SH/Mn-surface-functionalized MOF Multifunctional Adsorbent for As(III) Efficient Removal from Wastewater
Arsenic (As) contamination poses severe environmental risks, especially for developing countries. In this paper, an innovative binary (Mn and -SH) multifunctional adsorbent, ZIF-67-SH@Mn, was successfully synthesized as a prospective absorbent to efficiently remove As(III) from wastewater. The structure of ZIF-67-SH@Mn was characterized before and after the adsorption of As(III) using SEM–EDS, FTIR, BET, pH pzc and XRD. SEM–EDS confirmed the successful introduction of Mn and S, BET analysis revealed a high specific surface area of 197.21 m 2 /g, and FTIR demonstrated the key role of -SH groups in As(III) coordination. These findings indicate that Mn oxidation and -SH bonding synergistically enhance As(III) removal. The leaching experiment showed that the release amounts of Mn 2 ⁺ and Co 2 ⁺ from the adsorbent within 48 h complies with national standards. Batch adsorption experiments determined the optimal conditions: initial concentration 1 mg/L, temperature 298 K, pH 5, reaction time 4 h, and using an ultra-low adsorbent dosage ZIF-67-SH@Mn only 0.2 g/L, achieving As(III) removal efficiency of 70.33% and a maximum adsorption capacity of 21.84 mg/g. The adsorbent achieved 79.36% As(III) removal efficiency in river (RW) and wine water (WW), with RW ≥ WW ≥ DI performance regardless of initial concentration. The adsorption of As(III) by ZIF-67-SH@Mn followed pseudo-second-order kinetics and the Langmuir model, indicating a chemisorption-dominated and monolayer adsorption process. Thermodynamic analysis revealed a spontaneous and endothermic process. The intraparticle diffusion model indicated that particle internal diffusion not only determines the adsorption process but also plays an important role in surface adsorption in the rate-determining step. The adsorption mechanism of ZIF-67-SH@Mn for As(III) involved electrostatic adsorption, multifunctional group interactions (including -NH, -OH, -SH), and oxidation. ZIF-67-SH@Mn exhibits excellent As(III) removal efficiency and is a highly efficient, low-cost adsorbent with good application prospects in wastewater remediation.
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