Application of natural and synthetic goethite for the removal of methylene blue from aqueous solutions

Abstract

Unregulated discharge of untreated effluents into the environment by industries constitutes one of the major sources of pollution. Adsorption technique was since discovered as a highly efficient and cheap technique for effluent detoxification. The search for an efficient, low-cost, and readily available adsorbent necessitated this study, which investigates the sorption of methylene blue (MB) from aqueous solution by natural goethite (NGT) and synthetic goethite (SGT) particles using batch equilibrium technique. The effects of initial concentration, NGT particle size, adsorbent dosage and solution pH were evaluated, and found to have remarkable influence on the adsorption processes with optimum (pH of 12, concentration of 200 mg/L for MBNGT, 250 mg/L for MB-SGT and 0.112 mm mesh for NGT). The adsorption characteristics were quite similar, though with the adsorption capacities of 1.826 mg/g (NGT) and 27.322 mg/g (SGT). Results of isotherm modeling revealed the order of fittings; Langmuir (R2 = 0.9727) > Freundlich (0.9323) > Temkin (0.8113) for MB-NGT and Temkin (0.9217) > Freundlich (0.9171) > Langmuir (0.8529) for MB-SGT. An evaluation of isotherm investigation results with those of the kinetics and thermodynamic study (Ugbe & Abdus-Salam, 2020), suggest a combined physisorption and chemisorption mechanism. Therefore, this study provides useful information on the application of both goethite forms for MB removal.

Keywords

• adsorption
• natural goethite
• synthetic goethite
• methylene blue
• isotherms