Preparation of Fe@GAC and Fe@GAR and Their Application for Removal of Crystal Violet from Wastewater

Abstract

Two types of granular adsorbents-supported zero-valent iron (ZVI) were prepared and applied to remove crystal violet (CV). One type of ZVI was synthesized by the chemical reduction method and deposited on the surface of granular porous adsorbent (Fe@GAC). The other type of ZVI was synthesized by direct reduction of iron ore tailing powder with the coke in high temperature reducing atmosphere and was embedded in granular porous adsorbent (Fe@GAR). Fe@GAC and Fe@GAR were characterized by SEM, EDX, XRD, FTIR, and BET. The effect of parameters like contact time, initial CV concentration, pH values, and temperature on the removal of CV was investigated. According to the results, the Langmuir model was in good agreement with the experimental data, where the maximum removal capacity of Fe@GAC and Fe@GAR was found to be 95.24 mg/g and 123.45 mg/g at 293 K, respectively. The kinetic studies indicated that the pseudo-second-order kinetic model agreed well with the experimental data. Thermodynamic parameters were calculated and analyzed, which suggested that the removal processes were spontaneous and endothermic. The mechanism of CV removal by Fe@GAC and Fe@GAR included adsorption and simultaneous chemical reduction. Compared with Fe@GAC, Fe@GAR owned more amount of ZVI, larger specific surface area and higher removal capacity, which made it a more promising adsorbent in wastewater treatment.