F U L L PA P ER

A new one-dimensional coordination polymer synthesizedfrom zinc and guanazole: Superior capture of organicarsenics

Chao-Yang Wang | Xiu-Wu Zhang | Jia-Wei Wang | Huifen Fu |

Peng Wang | Chong-Chen Wang

Beijing Key Laboratory of FunctionalMaterials for Building Structure andEnvironment Remediation, BeijingUniversity of Civil Engineering andArchitecture, Beijing, 100044, China

CorrespondenceChong-Chen Wang, Beijing KeyLaboratory of Functional Materials forBuilding Structure and EnvironmentRemediation, Beijing University of CivilEngineering and Architecture, Beijing100044, China.Email: wangchongchen@bucea.edu.cn

Funding informationBeijing Natural Science Foundation,Grant/Award Number: No. 8202016;BUCEA Post Graduate Innovation Project,Grant/Award Number: PG2019036;Beijing University of Civil Engineeringand Architecture Post GraduateInnovation Project, Grant/AwardNumber: PG2019036; Beijing TalentProject, Grant/Award Number: 2019A22;Project of Construction of InnovationTeams and Teacher Career Developmentfor Universities and Colleges under BeijingMunicipality, Grant/Award Number:IDHT20170508; Great Wall ScholarsTraining Program Project of BeijingMunicipality Universities, Grant/AwardNumber: CIT&TCD20180323; the BeijingNatural Science Foundation, Grant/AwardNumber: 8202016

Organic arsenic compounds in the environment are a global threat to human

health. This threat has created the urgency to develop highly efficient adsor-

bents with both high adsorption capacity and versatile removal of different

arsenic compounds. A novel 1D zinc(II) coordination polymer, formulated as

Zn2(datrz)2(bpy)Cl2 (BUC-70) (datrz = guanazole, bpy = 4,40-bipyridine), wassuccessfully synthesized through slow evaporation at room temperature. BUC-

70 exhibited an excellent adsorption capacity toward p-arsanilic acid (p-ASA)

and roxarsone (ROX) in water, which could be ascribed to As–O–Zn bonding

interactions and strong hydrogen-bonding interactions between the organic

arsenics and BUC-70. The maximum adsorption capacities toward p-ASA and

ROX were 738 and 937 mg�g−1, respectively. BUC-70 was effective in the

removal of p-ASA and ROX at low concentrations (<5 mg�l−1) from the simu-

lated p-ASA and ROX wastewater. Furthermore, the as-synthesized BUC-70

exhibited good adsorption property toward p-ASA and ROX in wastewater sim-

ulated by lake water and tap water. After adsorptive treatment using BUC-70,

the concentrations of both p-ASA and ROX were lower than the required con-

centrations of the drinking water standard of the World Health Organization

and the surface water standard of China. Continuous-flow, fixed-bed column

experiments were performed using BUC-70 loaded on cotton as packing mate-

rial to explore the potential large-scale application.

KEYWORD S

adsorption, coordination polymer, p-arsanilic acid, roxarsone, water stability

1 | INTRODUCTION

Arsenic is one of the most toxic contaminants, whichmight lead to many human diseases such as cancers,DNA hypomethylation, and arsenicosis.[1] Arsenic pol-lution mainly results from the discharge of industrial

production, agricultural production, natural volcaniceruption, and some natural phenomena.[2] In mostarsenic-contaminated groundwater, arsenic concentra-tions range from 0.5 to 2.5 mg�l−1.[3, 4] In some indus-trial wastewater, it can reach more than 100 mg�l−1.[3]Till now, the inorganic trivalent arsenic (As(III)) and

Received: 10 January 2020 Revised: 20 February 2020 Accepted: 25 February 2020

DOI: 10.1002/aoc.5637

Appl Organometal Chem. 2020;34:e5637. wileyonlinelibrary.com/journal/aoc © 2020 John Wiley & Sons, Ltd. 1 of 13

https://doi.org/10.1002/aoc.5637

pentavalent arsenic (As(V)) pollutants have beenwidely studied.[5–7] However, increasing attentionshould be paid to the organic arsenic pollutants. p-Arsanilic acid (p-ASA) and roxarsone (ROX) are com-mon organic arsenic compounds widely used as feedadditives to control the intestinal parasites in domesticanimals.[4, 8, 9] However, p-ASA and ROX are oftendischarged into the environment along with animalfaeces.[10, 11] Generally, p-ASA and ROX are deemedas low-toxic compounds.[10, 11] However, they can bebiologically transformed into virulent As(III) andAs(V) in the environment,[10, 11] implying their poten-tial threat to the ecological environment and humanhealth. Traditional purification methods and technolo-gies of organic arsenics mainly include coagulation/precipitation, adsorption, ion exchange, membrane sep-aration, and chemical precipitation.[11, 12] Among thesemethods, adsorption is one of the most promisingmethods because of its high efficiency, low cost, andsimple operation.[12, 13] However, traditional adsorbentssuch as activated carbons, goethite, carbon nanotubes,and iron and aluminum oxides[2, 7, 11, 12] did not pos-sess the adequate adsorption capacity. Therefore, it isof great significance to synthesize new adsorbents withhigh efficiency and high adsorption capacity for remov-ing organic arsenics from the environment.

Coordination polymers (CPs) and metal–organicframeworks (MOFs), new classes of crystalline porousmaterials, have been widely used in adsorption,[14, 15]

separation,[16] drug delivery[17, 18] and catalysis,[19–21] gasstorage,[22] and fluorescent sensors.[23–25] CPs as adsor-bents had attracted great interest because of their advan-tages, exceeding traditional zeolite materials, such ashuge surface area, high specificity, and adsorption capac-ity as well as the ease of fabrication.[22, 26] So far, manyattempts have been made to use CPs as efficient adsor-bents to eliminate As(III) and As(V) from the environ-ment.[12, 13, 27, 28] However, less attention has been paidto the adsorptive removal of p-ASA and ROX.[12, 29]

Therefore, it is essential to study CPs as adsorbents toremove p-ASA and ROX from the environment.

As previously reported, the adsorption capacities oforganic arsenics by CPs mainly depended on electrostaticinteractions, coordination bonding interactions, π–π*stacking, and hydrogen-bonding interactions.[12, 13, 30]

The amine group in p-ASA can be an important factor inenhancing the adsorptive affinity through strengtheningthe coordination bonds, π–π* stacking, and forming newadsorption sites through hydrogen-bonding synergisticadsorption effect.[29] Therefore, designing an MOF con-taining amine groups may be an ideal strategy for theefficient removal of organic arsenic pollutants at low con-centrations.[31] As the content of organic arsenics in real

organic arsenic wastewater is relatively low(<5 mg�l−1),[29] it is important to synthesize a new adsor-bent for removing organic arsenic at low concentrations.Guanazole, namely 3,5-diamino-1,2,4-triazole (Hdatrz),exhibits five potential coordination sites, which canbridge metal ions in different coordination modes. Todate, some CPs (or MOFs) synthesized using guanazolewith different topological structures have been reported,such as [Zn2(btc)(datrz)]n,

[32] [Zn2(btec)(Hdatrz)]n,[32]

and [Cd3(datrz)6(H2O)2].[33] In this work, guanazole was

used as an organic ligand to synthesize a new 1D zincCP, Zn2(datrz)2(bpy)Cl2 (BUC-70), for the efficientremoval of p-ASA and ROX. BUC-70 not only exhibitedexcellent adsorption capacity for p-ASA and ROX butalso presented the efficient removal of trace p-ASA andROX (0.5 mg�l−1).

2 | EXPERIMENTAL

2.1 | Synthesis

Zn(NO3)2�6H2O (1.0 mmol, 0.2975 g), Hdatrz (1.0 mmol,0.0991 g), and 4,40-bipyridine (bpy, 1.0 mmol, 0.1562 g)were dissolved in deionized water (500.0 ml), which wasslowly vaporized at room temperature for 30 days. Theyellow crystals of BUC-70 were obtained (yield 60%)using Zn(NO3)2�6H2O and then washed with deionizedwater and ethanol. BUC-70 was quickly synthesized bymixing Zn(NO3)2�6H2O (10 mmol, 2.9750 g), Hdatrz(10 mmol, 0.9910 g), bpy (1 mmol, 1.5620 g), anddeionized water (400 ml); then the solution was stirred ina 500-ml glass beaker for 40 min. Anal. calc. for BUC-70(C14H16Cl2N12Zn2): C, 30.32%; H, 2.89%; N, 30.32%.Found: C, 30.36%; H, 2.98%; N, 30.20%. IR (KBr) cm−1:3432, 3347, 3193, 3090, 1622, 1606, 1560, 1531, 1490,1414, 1394, 1321, 1284, 1220, 1140, 1108, 1067, 1011,972, 843, 816, 768, 728, 677, 639, 625, 612, 557, 483.

2.2 | Synthesis of BUC-70@cotton

BUC-70@cotton was fabricated using the fast synthesismethod except for the addition of 2.0 g of cotton fibers.BUC-70@cotton was washed with deionized water toremove the loose-bound BUC-70 and dried in a vacuumoven at 333 K for 12 h. The BUC-70 content of BUC-70@cotton was calculated as 0.2 g�g−1 using the massincrease of the cotton after the load process.

2.3 | Adsorption experiments

For the adsorption kinetics and thermodynamics experi-ment, 200.0 ml of organic arsenic solutions with different

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concentrations ranging from 10 to 300 mg�l−1 (pH = 7 forp-ASA and pH = 5 for ROX) and 40 mg of BUC-70 weremixed in a conical flask and constantly shaken (170 rpm)for 48 h. Then the solutions were filtered through a0.20-μm filter, and the residual organic arsenic concen-trations of the filtrates were determined using an ICP-500inductively coupled plasma optical emission spectrometer(Focused Photonics Inc., Hangzhou, China). To investi-gate the influence of coexisting inorganic ions, theadsorption experiments were performed using simulatedwastewater containing organic arsenics (p-ASA andROX) with an initial concentration of 30 mg�l−1. Thethree-dimension excitation emission matrix (3D EEM)fluorescence spectra of lake water and tap water wererecorded using a Hitachi F-7000 and Techcomp FL970spectrophotometer at room temperature.

2.4 | Breakthrough experiments

Breakthrough experiments were conducted using a glasscolumn, in which a desired amount of BUC-70@cottonsample (2 g, containing about 0.2 g of BUC-70) waspacked into the column. Then, the p-ASA or ROX

solution (1 mg�l−1) was pumped through the column top-down at a flow rate of 2 ml�min−1.

3 | RESULTS AND DISCUSSIONS

3.1 | Crystal structure description

The asymmetric unit of 1D BUC-70 was formed usingtwo cationic Zn2+ ions, two bpy ligands, two datrzligands, and two chloridions. As shown in Figure 1a, thedatrz ligand adopted the bidentate-bridging mode to linktwo zinc atoms. The Zn2+ atoms were tetrahedrally coor-dinated by two nitrogen atoms from one datrz ligand,one nitrogen atom from bpy ligand, and one chloridion.The Zn–N distance was in the range of 1.966(3)–2.081(3) Å, and Zn–Cl distance was 2.2242(12) Å, which werecomparable to previous reports.[34, 35] In BUC-70, the Zn2+ centers were coordinated by datrz ligands through thebidentate mode into a 1D zig-zag chain (Figure 1b) paral-lel to the ab plane. In addition, in BUC-70, the consecu-tive dimers were connected by an elaborate network ofhydrogen bonds (N4-H4B���N3 and N5-H5B���N3). The1D chains of BUC-70 were perpendicular to each other

FIGURE 1 (a) Highlight of the coordination polyhedron of the Zn(II) atoms; (b) the 1D chains of BUC-70; and (c) the packing view of

the 3D supramolecular structure of BUC-70 with the aid of hydrogen-bonding interactions

WANG ET AL. 3 of 13

in the ab plane, extending toward the c-axis to form a 3Dsupramolecular structure (Figure 1c). In the structure ofBUC-70, the carbon atoms (C3, C4, C6, and C7) and theircorresponding hydrogen atoms in bpy ligands are disor-dered in two positions, with a site-occupancy factor ratioof 0.58/0.42.

3.2 | Characterization

The experimental powder X-ray diffraction (PXRD) pat-terns of BUC-70 (Figure S1) matched well with the simu-lated one, implying the high water stability and phasepurity of the sample.[36] The Fourier-transform infrared(FT-IR) spectra of BUC-70 are shown in Figure S2; thebroad absorption peak at 3193 cm−1 can be assigned toυs(N–H)NH,NH2, the absorption peak at 3347 cm−1 was asso-ciated with υas(N–H)NH,NH2 of the guanazole ligand, andthe absorption peak at 3432 cm−1 was associated withυ(N–H)NH,NH2 and υ(O–H)H2O. Besides these, a medium-to-strong band in the range of 1615–1680 cm−1 and amedium band in the range of 1400–1490 cm−1 wereobserved; both of them were associated with υ (ZnN) orring stretching vibrations and δ(N–H)NH,NH2 of theguanazole ligand.[37] The strong bands at 1011, 1067,1108, and 1145 cm−1 were attributed to the bendingvibration of the hydroxyl group bound to zinc atoms (Zn–OH).[38] The thermal stability of BUC-70 was tested usingthermogravimetric analysis from 323 K to 1073 K underair flow. As shown in Figure S3 and Table S4, the thermaldecomposition process of the as-synthesized BUC-70 canbe divided into three stages. The initial weight loss of27.43% (calculated 28.16%) at ~630 K can be attributed tothe removal of 4,40-bipyridine. The second weight loss of34.72% (calculated 35.37%) in the range began at 712 K,corresponding to the removal of two L ligands. The thirddecomposition process began at 823 K, in which theweight loss of 10.00% can be associated with the removal

of two chlorine atoms (calculated 12.80%). The final resi-due of 28.03% (calculated 29.37%) after 1073 K was attrib-uted to the formation of ZnO, in which Zn was 23.59%,which was in good agreement with the Zn content inZn2(datrz)(bpy)Cl2 (calculated 23.60%). Furthermore,PXRD of the residue of BUC-70 is shown in Figure S4,confirming that the final residue was ZnO(PDF#04-001-7297). Based on the scanning electronmicroscope (SEM) observations (Figure S5), the pureBUC-70 exhibited stacked cube morphology with thelamellar laminated structures, and the lamellar shapecrystal size was ~2.1 μm × 2.3 μm with a thickness~0.5 μm. The specific surface areas and porosity of BUC-70 were analyzed using N2 gas adsorption/desorption iso-therms (Figure S6). The Brunauer–Emmett–Teller sur-face areas of the prepared BUC-70 were 8.76 m2�g−1, andthe mesopore volume was 0.02 cm3�g−1 (BJH, Barrett-Joyner-Halenda).[39]

3.3 | Effect of pH

It is well known that the pH value of the solution is oneof the key operating factors in practical water treat-ment.[40] The crystallinity of BUC-70 was stable in aque-ous solution with a wide pH range from 5 to 11, whichcan be affirmed by PXRD results (Figure S1). To evaluatethe effects of pH on the adsorptive removal of p-ASA andROX over BUC-70, a series of experiments were per-formed at pH range from 5.0 to 11.0 (Figure 2). It wasfound that the adsorption performances of p-ASAincreased with the increase in pH up to 7.0 and thendecreased significantly, whereas the adsorption capacitiesof ROX decreased rapidly with pH (Figure 2a), which canbe ascribed to the negative zeta potentials of BUC-70 inthe pH range of 5.0–11.0. As shown in Figure 2b, the sur-face charge of BUC-70 was negative at pH range from 5.0to 11.0, and the pKa of p-ASA and ROX was 1.9, 4.1, 9.2and 3.43, 6.38, 9.67, respectively (Figure S7).[29, 41]

FIGURE 2 (a) Effect of pH on p-ASA and ROX adsorption by BUC-70 and (b) zeta potential of BUC-70 at different pH

4 of 13 WANG ET AL.

Meanwhile, the maximum adsorption capacity was stillat a high level in a wide pH range (Figure 2). Therefore,electrostatic interactions are not responsible for itsadsorption activities.[41]

3.4 | Kinetic study

The time-dependent adsorption profiles of p-ASA andROX onto BUC-70 are shown in Figure 3. It could befound that the adsorption equilibrium time of p-ASA and

ROX onto BUC-70 was ~5 h and ~3 h, respectively,which were similar to other MOF-based adsorbents suchas MIL-68(In) (~6 h)[42] and MIL-101-(OH)3 (6~12 h).[30]

The corresponding experiments were performed for 48 hto ensure that equilibrium was reached.

As shown in Figure 4, adsorption kinetics data wereobtained using pseudo-first-order and pseudo-second-order models (equations S2 and S3). Kinetic parametersand correlation coefficients are shown in Tables S5 andS6. The high correlation coefficient R2 values (≥0.99) ofthe pseudo-second-order kinetic model indicated that

FIGURE 3 Effects of contact time on the adsorption capacity of (a) p-ASA and (b) ROX by BUC-70

F IGURE 4 Adsorption kinetics of BUC-70 for (a) p-ASA and (b) ROX

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adsorption behaviors of p-ASA and ROX onto BUC-70were more appropriately described by the pseudo-second-order model.[43] In addition, the calculated qe values(734.73 and 843.20 mg�g−1, respectively) of p-ASA andROX were consistent with the experimental values(728.02 and 841.72 mg�g−1, respectively) and confirmedthat p-ASA and ROX adsorption over BUC-70 followedthe pseudo-second-order kinetic model,[44] indicatingthat the adsorption process may be a chemisorptionprocess.[45]

3.5 | Adsorption isotherms

The maximum adsorption capacity (qm) was one of themost vital parameters to assess the adsorption perfor-mance of an adsorbent.[44] To obtain the qm values ofBUC-70 for p-ASA and ROX, the adsorption isothermsprocedures over BUC-70 were carried out using a seriesof concentrations of p-ASA or ROX ranging from 10 to300 mg�l−1 for 48 h. The adsorption isotherms of BUC-70for p-ASA and ROX (288 K, 298 K, and 308 K) are shownin Figure 5.

To understand the interactive behavior betweenBUC-70 and organic arsenic compounds (p-ASA andROX), Langmuir and Freundlich models (equations S4and S5, ESI) were used to analyze the obtained adsorp-tion isotherms (Figure 6). All the R2 values of the Lang-muir model were >0.99, being much better than those ofthe Freundlich model. These results indicated thatadsorption of p-ASA and ROX onto BUC-70 was consis-tent with the Langmuir model.[43, 44] The maximumadsorption capacities (qm) calculated using Langmuirplots are shown in Tables S7 and S8. The maximumadsorption capacities of p-ASA and ROX by BUC-70 were738 and 937 mg�g−1, respectively, which were substan-tially larger than most of the reported MOF-basedadsorbents (Table 1). As far as we know, the qm value of

BUC-70 for ROX is the highest among the previouslyreported values.[12, 44] Therefore, BUC-70 may be com-petitive adsorbents for the practical removal of p-ASAand ROX.

To calculate the standard free energy change (ΔG�,kJ�mol−1), enthalpy change (ΔH, kJ�mol−1), and entropychange (ΔS, J�mol−1�K−1), the adsorption was furtherdetermined to obtain isotherms at 288 K, 298 K, and308 K. The thermodynamic parameters are shown inTables S9 and S10. The negative values for ΔG� (from−26 to −32 kJ�mol−1) indicated that the adsorption pro-cess may be controlled by both physical and chemicalsorption.[34] The positive values of ΔH� (17.74 and81.73 kJ�mol−1 for p-ASA and ROX, respectively) con-firmed that the adsorption process was endothermicunder ambient conditions.[15] The positive values of ΔS�

(18.56 and 128.53 J�mol−1�K−1 for p-ASA and ROX,respectively) indicated the increased randomness at thesolid solution and the affinity of p-ASA and ROX ontoBUC-70.[48]

3.6 | Adsorption behavior of BUC-70toward low concentration of simulatedorganic arsenic wastewater samples

The adsorption capacity of BUC-70 at low organic arsenicconcentration is crucial for the practical treatment ofdrinking water[4]; 0.5 mg�l−1 (p-ASA and ROX) wasselected as the experimental concentration. As shown inFigure 7a,b, the organic arsenic concentration decreasedto 1.10 μg�l−1 (p-ASA) and 4.76 μg�l−1 (ROX) just in 5 min(0.2 g�l−1 of BUC-70), which was much lower than theWorld Health Organization standard for drinking water(10 μg�l−1).[29] To investigate the effect of the coexistingions on the adsorption capacities of BUC-70 for p-ASAand ROX, F−, NO3

−, SO42−, and PO4

3− withCinitial = 0.02 M were selected as foreign ions.[41, 43] As

FIGURE 5 Adsorption isotherms of BUC-70 for (a) p-ASA and (b) ROX

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TABLE 1 Comparison of p-ASA and ROX elimination from simulated wastewater using different metal–organic framework

(MOF)-based adsorbents

Arsenicspecies

MOF-basedmaterials

Adsorption capacity(mg�g−1) Removal mechanisms References

p-ASA Mesoporous ZIF-8 791.1 Complexation 46

p-ASA MOF-808(F) 621.1 Electrostatic, hydrogen bonding, π–π*stacking

44

p-ASA UiO-67 484 Complexation, hydrogen bonding, π–π*stacking

29

p-ASA NH2-MIL-68(In) 401.6 π–π* stacking, hydrogen bonding 42

p-ASA MIL-100(Fe) 366.0 Complexation 47

p-ASA MIL-101(OH)3 238.0 Hydrogen bonding, electrostatic interaction 30

p-ASA UiO-67-NH2 178 Complexation, hydrogen bonding, π–π*stacking

29

p-ASA MIL-101(OH) 163.0 Hydrogen bonding, electrostatic interaction 30

p-ASA BUC-70 738 Complexation (coordination), hydrogenbonding

This work

ROX UiO-66-20 730.0 Complexation 43

ROX MOF-808(F) 709.2 – 44

ROX MIL-100(Fe) 387.0 Complexation 47

ROX BUC-70 937 Complexation, hydrogen bonding This work

FIGURE 6 (a) Langmuir and (b) Freundlich models of p-ASA onto BUC-70, (c) Langmuir and (d) Freundlich models of ROX onto

BUC-70

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shown in Figure 7c,d, F−, NO3−, and SO4

2− exerted a neg-ligible effect on the adsorption capacity of BUC-70 for p-ASA and ROX, whereas PO4

3− strongly inhibited theadsorption behavior of BUC-70. As reported previously,phosphate and arsenate are chemically similar, whichcan form inner-sphere complexes with the hydroxylgroups on the surface of the adsorbent.[49–51] The pres-ence of PO4

3− greatly weakened the adsorption capacity

of BUC-70for p-ASA and ROX, which might be attributedto the competition between PO4

3− and organoarsenic.[41]

To further investigate the influence of the coexisting inor-ganic ions and dissolved organic matter (DOM), a seriesof aqueous p-ASA and ROX solutions prepared using tapwater and lake water were tested.[29, 41] The parametersof water quality and the 3D EEM fluorescence spectrumare shown in Table S12 and Figure 8, respectively.

FIGURE 7 (a) The relationship between the concentration of p-ASA and adsorption time (0.5 mg�l−1, 298 K); (b) the relationshipbetween the concentration of ROX and adsorption time (0.5 mg�l−1, 298 K); (c) effect of coexisting ions on p-ASA adsorption; and (d) effect

of coexisting ions on ROX adsorption

FIGURE 8 The three-dimension excitation emission matrix fluorescence spectrum of (a) tap water samples and (b) lake water samples

8 of 13 WANG ET AL.

According to the 3D EEM fluorescence spectrum of realwater samples, DOM in tap water and lake water showspeaks at A, C, and T, respectively, indicating that themajor fluorescent components of DOM in tap water andlake water are UV humic-like, Visible humic-like, andprotein-like tryptophan, respectively.[52, 53] The resultsrevealed that the adsorption capacity of BUC-70 for p-ASA and ROX was slightly inhibited in the simulatedwastewater (Figure 7a,b), which may be attributed to theinfluences from the coexisting inorganic ions andDOM.[41] However, the elimination efficiency was still94% within 60 min, indicating the great prospects for theapplication of BUC-70 for p-ASA and ROX adsorption innatural water.

The SEM (Figure 9a,b) and elemental mapping(Figures S8 and S9) of cotton and BUC70@cotton indi-cated that BUC-70 was the successful load on the surfaceof cotton, which is similar to the previous reports.[54–56]

After BUC-70 was loaded onto cotton, new peaksappeared at 1400–1490 and 1615–1680 cm−1 (Figure S10),which corresponded to υ (ZnN) or ring stretching vibra-tions and δ(N–H)NH,NH2 of the guanazole ligand.[37] Thisconfirmed the interaction between BUC-70 andcotton.[54–56] As shown in Figure S11, pristine cottoncould not remove organic arsenics from water, whereas

with BUC-70 particles embedded onto the cotton matrix,the adsorption capacity increased dramatically, indicatingthe removal of organic arsenics primarily by the sorptionof BUC-70.[55]

The breakthrough curves of p-ASA and ROX overBUC-70@cotton are shown in Figure 9c,d. The resultsindicate that the residual concentration maintained a sat-isfactory level in the effluent (Ct < 30 μg�l−1) for a longtime (980 min for p-ASA and 2100 min for ROX), indicat-ing BUC-70@cotton might be a promising adsorptionmaterial for large-scale application.[47] Notably, theadsorption capacity of BUC-70@cotton was almostexhausted after 90 h of continuous inflow of ROXsolution.

3.7 | Mechanism of p-ASA and ROXadsorption on BUC-70

Generally, electrostatic interactions, hydrogen bonding,π–π* stacking, coordination, and hydrophobic interac-tions were used to explain the liquid-phase adsorptionmechanism of organic compounds over CPs.[30, 57, 58]

To obtain an insight into adsorption mechanism, PXRD,FT-IR, SEM, elemental mapping, and X-ray

FIGURE 9 (a) Scanning electron microscope (SEM) image of cotton; (b) SEM image of BUC-70 crystals grown inside cotton fibers;

(c) breakthrough curves of ROX over BUC-70@cotton (Ce is the concentration of p-ASA in the effluent at time); and (d) breakthrough

curves of p-ASA over BUC-70@cotton (Ce is the concentration of ROX in the effluent at time)

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Photoelectron Spectroscopy (XPS) were used to analyzethe composition, morphology, and microstructure ofBUC-70 for p-ASA and ROX adsorption. The PXRD ofBUC-70 before and after adsorption of p-ASA and ROXare shown in Figure S12; several new peaks appearedafter the adsorption process, implying that some newphase may come into being.[40] The PXRD patternpeaks of the final products matched with those of(Zn3(AsO4)2)3(H2O)4 (PDF#97-005-9279), implying theformation of (Zn3(AsO4)2)3(H2O)4.

[59] The SEM observa-tions (Figure S5) also indicated that the morphology ofBUC-70 exhibited a slight change after the adsorptionprocess, which was consistent with the PXRD results(Figure S12). The FT-IR spectra of BUC-70 before andafter the test are shown in Figure S2. After the adsorp-tion test, the intense adsorption peaks of the as-synthesized BUC-70 at 3432 and 3347 cm−1 (–NH2 and–OH)[60, 61] became a broad peak (3354 and 3405 cm−1

for p-ASA and ROX, respectively), which might beattributed to the formation of abundant surface activesites, such as Zn–OH and N–H, produced by the disso-ciative adsorption of water.[61] As the previous reportsindicate, the new bands at 897, 850, and 781 cm−1

(BUC-70 after adsorbing p-ASA) and 897, 851, and781 cm−1 (BUC-70 after adsorbing ROX) might beattributed to the formation of Zn–O–As bonds.[62–64]

The small peak at 656 cm−1 (after adsorption of p-ASAand ROX) might be attributed to the asymmetricstretching of As–OH.[65] The elemental mapping results(Figure 10) confirmed the presence of arsenic on BUC-70 after the adsorption test.

XPS was conducted to study the exchange of arsenicspecies on the surface of BUC-70 (Figure 11). As shownin Figure 11a, a new As3d core level peak appeared inthe wide-scan XPS spectra of BUC-70 after p-ASA and

ROX adsorption, indicating the immobilization of p-ASA and ROX on BUC-70.[7] As shown in Figure 11b,there were almost no π–π* stacking peaks on the C1sspectra of BUC-70 before and after adsorption of p-ASAand ROX, indicating that π–π* stacking was not thedominant force for the adsorption process.[29] The O1sspectra (Figure 11c) of pristine BUC-70 consisted oftwo peaks at 532.47 and 531.19 eV, which wereassigned to H2O and Zn–OH bonds.[41, 61, 66] Comparedwith the spectra of virgin BUC-70, new peaks at530.66 eV (BUC-70 after adsorbing p-ASA) and530.96 eV (BUC-70 after adsorbing ROX) verify the for-mation of the Zn–O–As bond.[61, 67] Therefore, the firstlikely adsorption sites on BUC-70 were the Zn–OHgroups, which provided four Zn–OH groups in a unitZn2 cluster to attract a maximum of four equivalentorganic arsenic species.55

It is obvious that BUC-70 and organic arsenics (p-ASA and ROX) had obvious ample H-donor and H-acceptor moieties, such as –NH2 and –OH.[29, 41] Thus,hydrogen bonding might be a possible contribution toadsorption.[30, 44, 61] As shown in Figure 11d, afteradsorption of p-ASA and ROX, hydrogen-bonded –NH2

groups appeared on the N1s spectra of BUC-70, indi-cating that hydrogen bonding between BUC-70 andorganic arsenics (p-ASA and ROX) also played animportant role in the adsorption process.[29] As shownin Figure 2, with the increase in pH, the maximumadsorption capacity gradually decreased, which mightbe due to the highly negative charge on the surface ofBUC-70 preventing the interaction (coordination) withthe negative adsorbate.[30] In conclusion, hydrogen-bonding and coordination interactions (Zn–O–As)enabled BUC-70 to exhibit superior adsorption abilitiesto p-ASA and ROX (Figure 12).

FIGURE 10 Elemental mapping of BUC-70 before and after adsorption of p-ASA and ROX

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4 | CONCLUSIONS

In summary, a new water-stable CP (BUC-70) with out-standing adsorption property was designed, synthesized,

and used for the efficient removal of p-ASA and ROX.The adsorption kinetics of p-ASA and ROX over BUC-70satisfied the pseudo-second-order kinetic model, and theadsorption isotherms followed the Langmuir model.

FIGURE 11 Wide-scan XPS spectra of (a) BUC-70 before and after adsorption of p-ASA and ROX; (b) C1s XPS spectra of BUC-70before and after adsorption of p-ASA and ROX; (c) O1s XPS spectra of BUC-70 before and after adsorption of p-ASA and ROX; and (d) N1s

XPS spectra of BUC-70 before and after adsorption of p-ASA and ROX

FIGURE 12 Mechanism of p-ASA

and ROX adsorption on BUC-70

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BUC-70 performed well in the adsorption of p-ASA andROX in simulated wastewater (arranged by naturalwater) with various coexisting ions and DOM. BUC-70exhibited a high removal capacity for p-ASA and ROXfrom the simulated organic arsenic wastewater atlow concentrations (0.5 mg�l−1). Although BUC-70cannot be recycled, BUC-70@cotton can ensure that theresidue is still attached to cotton after adsorption satura-tion. Therefore, the arsenics can be extracted by BUC-70@cotton from treated water without producing anysludge at the bottom of the water. Finally, CPs and MOFsmight provide potential opportunities to treat pollutedwater.

ACKNOWLEDGMENTSThis work was supported by the Beijing Natural ScienceFoundation ( NO. 8202016), Great Wall Scholars TrainingProgram Project of Beijing Municipality Universities(CIT&TCD20180323), Project of Construction of Innova-tion Teams and Teacher Career Development for Univer-sities and Colleges under Beijing Municipality(IDHT20170508), Beijing Talent Project (2019A22),and BUCEA Post Graduate Innovation Project(PG2019036).

ORCIDChong-Chen Wang https://orcid.org/0000-0001-6033-7076

REFERENCES[1] K. Jomova, Z. Jenisova, M. Feszterova, S. Baros, J. Liska,

D. Hudecova, C. J. Rhodes, M. Valko, J. Appl. Toxicol. 2011,31, 95.

[2] T. Yang, Y. Liu, L. Wang, J. Jiang, Z. Huang, S.-Y. Pang,H. Cheng, D. Gao, J. Ma, Water Res. 2018, 147, 321.

[3] T. S. Y. Choong, T. G. Chuah, Y. Robiah, F. L. G. Koay,I. Azni, Desalination 2007, 217, 139.

[4] X. Liu, W. Zhang, Y. Hu, H. Cheng, Microchem. J. 2013,108, 38.

[5] P. Maria, M. Xiaoguang, G. P. Korfiatis, J. Chuanyong, Envi-ron. Sci. Technol. 2006, 40, 1257.

[6] Y.-N. Wu, M. Zhou, B. Zhang, B. Wu, J. Li, J. Qiao, X. Guan,F. Li, Nanoscale 2014, 6, 1105.

[7] Q. Hu, Y. Liu, X. Gu, Y. Zhao, Chemosphere 2017, 181, 328.[8] X. Liu, W. Zhang, Y. Hu, E. Hu, X. Xie, L. Wang, H. Cheng,

Chemosphere 2015, 119, 273.[9] Y. Hu, W. Zhang, H. Cheng, S. Tao, Environ. Sci. Technol.

2017, 51, 3508.[10] C. Y. Wang, H. Fu, P. Wang, C. C. Wang, Appl. Organomet.

Chem. 2019, 33, e5021.[11] D. Mohan, C. U. Pittman Jr., J. Hazard. Mater. 2007, 142, 1.[12] C. Wang, J. Luan, C. Wu, Water Res. 2019, 158, 370.[13] L. Hao, N. Wang, C. Wang, G. Li, Chemosphere 2018, 202, 768.[14] X. Wang, W. Liu, H. Fu, X.-H. Yi, P. Wang, C. Zhao, C.-

C. Wang, W. Zheng, Environ. Pollut. 2019, 249, 502.

[15] J. J. Li, C. C. Wang, H. Fu, J. R. Cui, J. R. Li, Dalton Trans.2017, 46, 10197.

[16] J. Zhang, C. C. Wang, P. Wang, Y. L. Cao, RSC Adv. 2016, 6,73595.

[17] K. Deng, Z. Hou, X. Li, C. Li, Y. Zhang, X. Deng, Z. Cheng,J. Lin, Sci. Rep-UK 2015, 5, 7851.

[18] M.-X. Wu, Y.-W. Yang, Adv. Mater. 2017, 29, 1606134.[19] Y.-C. Zhou, X.-Y. Xu, P. Wang, H. Fu, C. Zhao, C.-C. Wang,

Chinese J. Catal. 2019, 40, 1912.[20] D.-D. Chen, X.-H. Yi, C. Zhao, H. Fu, P. Wang, C.-C. Wang,

Chemosphere 2020, 245, 125659.[21] H. Liu, C. Xu, D. Li, H. L. Jiang, Angew. Chem. Int. Ed. 2018,

57, 5379.[22] M. Inukai, M. Tamura, S. Horike, M. Higuchi,

S. Kitagawa, A. K. Nakamura, Angew. Chem. Int. Ed. 2018, 57,8687.

[23] D.-M. Chen, C.-X. Sun, Y. Peng, N.-N. Zhang, H.-H. Si, C.-S. Liu, M. Du, Sensor. Actuat. B-Chem. 2018, 265, 104.

[24] C.-Y. Wang, B. Yu, H. Fu, P. Wang, C.-C. Wang, Polyhedron2019, 159, 298.

[25] X.-X. Song, H. Fu, P. Wang, H.-Y. Li, Y.-Q. Zhang, C.-C. Wang, J. Colloid, Interf. Sci. 2018, 532, 598.

[26] J. W. Shin, A. R. Jeong, S. Jeoung, H. R. Moon,Y. Komatsumaru, S. Hayami, D. Moon, K. S. Min, Chem.Commun. 2018, 54, 4262.

[27] W. Yu, M. Luo, Y. Yang, H. Wu, W. Huang, K. Zeng, F. Luo,J. Colloid Interface Sci. 2019, 269, 264.

[28] Y. Jia-Le, Y. Yan-Hong, L. Ru-Ping, Q. Jian-Ding, Talanta2018, 190, 255.

[29] C. Tian, J. Zhao, X. Ou, J. Wan, Y. Cai, Z. Lin, Z. Dang,B. Xing, Environ. Sci. Technol. 2018, 52, 3466.

[30] M. Sarker, Y. S. Ji, S. H. Jhung, J. Hazard. Mater. 2017,335, 162.

[31] J.-B. Lin, J.-P. Zhang, X.-M. Chen, J. Am. Chem. Soc. 2010,132, 6654.

[32] P. Cui, X. Li, J. Mol. Struct. 2015, 1081, 182.[33] R.-B. Zhang, Z.-J. Li, Y.-Y. Qin, J.-K. Cheng, J. Zhang, Y.-

G. Yao, Inorg. Chem. 2008, 47, 4861.[34] F. X. Wang, X. H. Yi, C. C. Wang, J. G. Deng, Chinese J. Catal.

2017, 38, 2141.[35] J. J. Li, C. C. Wang, J. Guo, J. R. Cui, P. Wang, C. Zhao, Poly-

hedron 2018, 139, 89.[36] H. Atallah, M. E. Mahmoud, A. Jelle, A. Lough, M. Hmadeh,

Dalton Trans. 2018, 47, 799.[37] Z. Rui-Bo, L. Zhao-Ji, Q. Ye-Yan, C. Jian-Kai, Z. Jian, Y. Yuan-

Gen, Inorg. Chem. 2008, 47, 4861.[38] Y. Zhang, M. Yang, X.-M. Dou, H. He, D.-S. Wang, Environ.

Sci. Technol. 2005, 39, 7246.[39] W. Xiong, G. Zeng, Z. Yang, Y. Zhou, C. Zhang, M. Cheng,

Y. Liu, L. Hu, J. Wan, C. Zhou, R. Xu, X. Li, Sci. Total Environ.2018, 627, 235.

[40] Y. Gu, D. Xie, Y. Wang, W. Qin, H. Zhang, G. Wang,Y. Zhang, H. Zhao, Chem. Eng. J. 2019, 357, 579.

[41] Z. Li, X. Liu, W. Jin, Q. Hu, Y. Zhao, J. Colloid Interface Sci.2019, 554, 692.

[42] Y. Lv, R. Zhang, S. Zeng, K. Liu, S. Huang, Y. Liu, P. Xu,C. Lin, Y. Cheng, M. Liu, Chem. Eng. J. 2018, 339, 359.

[43] B. Li, X. Zhu, K. Hu, Y. Li, J. Feng, J. Shi, J. Gu, J. Hazard.Mater. 2016, 302, 57.

12 of 13 WANG ET AL.

[44] Z.-J. Lin, H.-Q. Zheng, Y.-N. Zeng, Y.-L. Wang, J. Chen, G.-J. Cao, J.-F. Gu, B. Chen, Chem. Eng. J. 2019, 378, 122196.

[45] K. S. Park, Z. Ni, A. P. Côté, J. Y. Choi, O. M. Yaghi, P. Natl.Acad. Sci. 2006, 103, 10186.

[46] B. K. Jung, J. W. Jun, Z. Hasan, S. H. Jhung, Chem. Eng. J.2015, 267, 9.

[47] J. W. Jun, M. Tong, B. K. Jung, Z. Hasan, C. Zhong,S. H. Jhung, Chem. A Eur. J. 2015, 21, 347.

[48] A. Özcan, S. Tunali, T. Akar, I. Kiran, J. Hazard. Mater. 2005,124, 200.

[49] C. Su, R. W. Puls, Environ. Sci. Technol. 2001, 35, 4562.[50] C. Su, R. W. Puls, Environ. Sci. Technol. 2001, 35, 1487.[51] H. Zeng, B. Fisher, D. E. Giammar, Environ. Sci. Technol.

2007, 42, 147.[52] P. G. Coble, Mar. Chem. 1996, 51, 325.[53] C. Zhao, C.-C. Wang, J.-Q. Li, C.-Y. Wang, P. Wang, Z.-J. Pei,

RSC Adv. 2015, 5, 73490.[54] X.-D. Du, X.-H. Yi, P. Wang, W. Zheng, J. Deng, C.-C. Wang,

Chem. Eng. J. 2019, 356, 393.[55] P. Wan, M. Yuan, X. Yu, Z. Zhang, B. Deng, Chem. Eng. J.

2019, 382, 122921.[56] J. Zhao, M. D. Losego, P. C. Lemaire, P. S. Williams, B. Gong,

S. E. Atanasov, T. M. Blevins, C. J. Oldham, H. J. Walls,S. D. Shepherd, Adv. Mater. Interfaces 2014, 1, 1400040.

[57] B. K. Jung, Z. Hasan, S. H. Jhung, Chem. Eng. J. 2013, 234, 99.[58] J. Hu, Z. Tong, Z. Hu, G. Chen, T. Chen, J. Colloid Interface

Sci. 2012, 377, 355.[59] F. Hawthorne, M. Cooper, Y. Abdu, N. Ball, M. Back, K. Tait,

Mineral. Mag. 2012, 76, 45.

[60] Z. Zhang, S. Xian, H. Xi, H. Wang, Z. Li, Chem. Eng. Sci. 2011,66, 4878.

[61] J. Li, Y.-n. Wu, Z. Li, B. Zhang, M. Zhu, X. Hu, Y. Zhang,F. Li, J. Phys. Chem. C 2014, 118, 27382.

[62] C. Wang, X. Liu, J. P. Chen, L. Kang, Sci. Rep. 2015, 5, 16613.[63] S. Hou, Y. N. Wu, L. Feng, W. Chen, Y. Wang, C. Morlay,

F. Li, Dalton Trans. 2018, 47, 2222.[64] C. O. Audu, H. G. T. Nguyen, C.-Y. Chang, M. J. Katz, L. Mao,

O. K. Farha, J. T. Hupp, S. T. Nguyen, Chem. Sci. 2016, 7,6492.

[65] N. Mahanta, J. P. Chen, J. Mater. Chem. A 2013, 1, 8636.[66] Z. Shujuan, L. Xiao-Yan, C. J. Paul, J. Colloid Interface Sci.

2010, 343, 232.[67] M. Jian, L. Bao, G. Zhang, R. Liu, X. Zhang, Colloids Surfaces

a. 2015, 465, 67.

SUPPORTING INFORMATIONAdditional supporting information may be found onlinein the Supporting Information section at the end of thisarticle.

How to cite this article: Wang C-Y, Zhang X-W,Wang J-W, Fu H, Wang P, Wang C-C. A new one-dimensional coordination polymer synthesizedfrom zinc and guanazole: Superior capture oforganic arsenics. Appl Organometal Chem. 2020;34:e5637. https://doi.org/10.1002/aoc.5637

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