A cost-effective approach for abatement of cyanide using iron-impregnated activated carbon: kinetic and equilibrium study

Abstract

The present study is devoted for eliminating cyanide from wastewater through adsorption onto a surface impregnated with iron. It is seen that the impregnation of iron improves the removal efficacy of cyanide. Ferric nitrate nonahydrate has been used as impregnating agent, and Corncob, a waste material, has been used as a progenitor for the preparation of adsorbent. For determining the optimum conditions for impregnation of iron, response surface methodology has been employed. Combined effect of weight ratio, time, and temperature has been tested, and optimum condition has been obtained with weight ratio (1.0), time (1.50 h), and temperature (400 °C), and the sample made at this condition is named as iron-impregnated activated carbon (IIAC). While studying the adsorptive behavior of IIAC in contrast to activated Corncob without impregnation (ACWI), it has been found that for a cyanide solution of 50 mg L−1, ACWI can remove only 61% of cyanide and IIAC is able to remove around 91% at a constant adsorbent dosage of 10 g L−1. The minimum (− 1) and maximum (+ 1) level of particle sizes (45–150 µm), adsorbent dosage (5–20 g L−1), and initial concentration (IC) of cyanide (5–50 mg L−1) on cyanide removal have been examined using ANOVA, at room temperature (25 °C) for knowing the dependence on the same. Maximum cyanide removal (99.58%) has been achieved at an optimum particle size of 100 µm, adsorbent dosage of 3.95 g L−1, IC of 27.5 mg L−1 at pH 7.5 with IIAC. Langmuir and Freundlich isotherm models have been used for analyzing equilibrium data where Freundlich isotherm has been suitable. Different kinetic models have been employed to fit the data. Pseudo-second-order kinetic model has been found to be most applicable.