Removal of nickel and methylene blue from aqueous solutions by steel slag as a low cost adsorbent

Abstract

Nowadays, wastewater from various industries contains a large number of harmful heavy metals and coloring agents, which have to be removed to restore the quality of the environment. In this study, the removal of nickel ions (Ni²⁺) and methylene blue (MB) from the aqueous solution using steel slag as a low cost adsorbent was investigated. The chemical and mineralogical compositions, as well as the surface area of slag, were analyzed by using X-ray fluorescence spectroscopy, X-ray diffraction, and the Brunauer-Emmett-Teller method (BET). The effect of several important parameters such as contact time, adsorbent dose, pH, temperature, and initial adsorbate concentration on the adsorption process was studied systematically by batch experiments. The adsorption data were well correlated with the Langmuir isotherm model by all samples. The maximum adsorption capacity of the raw slag samples was 36.49 mg/g for Ni²⁺ and increased from 0.68 to 1.98 mg/g for MB after being acid-activated. The determined thermodynamic parameters indicate that the adsorption of Ni2+ and MB on steel slag is spontaneous in nature, endothermic (for Ni²⁺), and exothermic (for MB).