Imidazole-modified clinoptilolite as an efficient adsorbent for removal of 2, 4, 6-trichlorophenol: fabrication, characterization, kinetic and isotherm studies

Chlorophenol compounds, especially trichlorophenols, are on the US environmental protection agency's list of priority pollutants due to the carcinogenicity and mutagenicity. In this study, for improving of the removal efficiency of 2, 4, 6- trichlorophenol (2, 4, 6-TCP) using a naturally based and eco-friendly adsorbent; raw clinoptilolite, acidic Clinoptilolite, modified clinoptilolite with silane and imidazole-modified clinoptilolite (ImidClino) was evaluated. Morphology of the modified adsorbent was analyzed using FE-SEM, TGA, XRD, FT-IR, BET and EDAX. Adsorption process of 2, 4, 6-TCP onto Imid-Clino adsorbent as solution pH, adsorbent dose, agitation speed, contact time, initial 2,4,6-TCP concentration and temperature was investigated. From the results, it has been observed that the highest removal efficiency is 86% at contact time of 3-hour, initial 2,4,6-TCP concentration of 30 mg/L, adsorbent dosage of 40 mg and agitation speed of 150 rpm at pH 5.0 that is related to ImidClino. The equilibrium data were studied using Langmuir, Freundlich, Radlich-Peterson, Temkin and Elovich isotherms. Moreover, kinetic syudies were evaluated by pseudo-first-order (PFO), pseudo- second order (PSO), intra- particle diffusion (IPD) and Elovich models. The results indicated that Langmuir-Freundlich isotherm and PSO model had the most agreement with the experimental data. Thermodynamic parameters showed the 2, 4, 6TCP adsorption onto Imid-Clino was exothermic and spontaneous. The desorption studies have shown that the removal efficiency of this contaminant after four stages of adsorption and desorption decreased about 4%. The obtained reaults confirmed that the Imid-Clino can be used as potential adsorbent in practical applications for removal of 2, 4, 6-TCP from industrial wastewater and other water contaminated with 2, 4, 6-TCP.