Abstract BACKGROUND This study evaluates a newly synthesized O ‐diaminopyridine‐based chitin composite (CHI‐DIPY) for the effective elimination of selenite (Se 4+ ) ions from polluted water. The adsorbent was tested using wastewater collected from an open‐pit coal mine containing an initial selenium concentration of about 3 mg/L. Successful synthesis and structural integrity of CHI‐DIPY were confirmed using FT‐IR, XPS, BET, SEM–EDX, TGA, 1 H‐NMR, 13 C‐NMR, and MS analyses. Key operational parameters, including pH, contact time, initial selenium concentration, adsorbent dosage, co‐ion interference, temperature, and elution conditions, were systematically optimized. RESULTS Under optimal conditions (25 °C, pH 4, 25 min contact time, and 250 mg/L initial Se concentration), CHI‐DIPY achieved a maximum adsorption capacity of 110 mg/g. Equilibrium data were best described by the Langmuir isotherm model, with a theoretical capacity of 109.98 mg/g. Kinetic studies followed a pseudo‐second‐order model, predicting a capacity of 123.45 mg/g. Thermodynamic analysis indicated that adsorption was spontaneous and exothermic (Δ H = −18.305 kJ mol −1 ; Δ G = −3.212 to −0.446 kJ mol −1 over 298–353 K). CHI‐DIPY exhibited strong selectivity for selenite in the presence of competing ions and demonstrated excellent reusability, with 99% selenium desorption using 1 M H 2 SO 4 . CONCLUSION CHI‐DIPY is a highly efficient, selective, and regenerable adsorbent for selenite removal. Application to real coal‐mine wastewater reduced selenium concentrations below WHO and EPA limits in a single treatment cycle, highlighting its strong potential for practical environmental remediation. © 2026 Society of Chemical Industry (SCI).
Abdelaziz et al. (Fri,) studied this question.
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