Adsorption of mercury(II) to volcanic rock: Characteristics, equilibrium, thermodynamics, regeneration and wastewater treatment applications

Abstract

Andesite was employed to effectively extract mercury(II) in aqueous solution. After evaluating its characteristics, andesite was characterized applying modern techniques such as FTIR, BET and TGA methods. The study employed SEM and TEM measurements to analyze the variation in the surface shape and crystallinity of the metal due to adsorption. Adsorbent quantity (0.05-1) mg, contact time (5-60) minutes, pH (2–10), temperature (25–60)°C, and dose [2.738, 4.413, 12.550, 15.520, 39.95] ppb, all affect the amount of removal that increases with the increase in contact time, pH, dose and temperature, but drops as the metal ion concentration rises . The ideal values for contact time, pH, metal ion concentration, dose, and temperature were found to be, respectively, 30 minutes, 8, 15.520 ppb, 0.4 mg, and 40°C. The calculation of thermodynamic parameters, including ΔH, ΔG, and ΔS, was imperative in establishing that the mechanism of heavy metal adsorption on andesite was endothermic, exhibiting a physical nature that escalated with temperature rise. The Freundlich adsorption equation's linear form is matched by the adsorption of mercury(II) on andesite, constant n was 1.85, 1.06, 1.1, and 1.1, whereas the Langmuir constant qm was found to be 1.85, 2.41, 3.54, and 2.28 mg/g at 25°C to 60°C. Furthermore, adsorption follows a pseudo-second-order, rate constant was 3.08, 3.24, 3.24 and 13 under the identical temperature conditions, as opposed to a first-order, rate constant was 4, 3, 2.6, and 2. Hg2+, NH4+, Cl-, Br-, NO3-, SO42-, Na+, K+, H2S, and CH3SH were all extracted from wastewater by this application.