Removal of methylene blue from aqueous solution using raw laterite: an adsorption study

Existing methods for dye removal have their limitations and can be expensive and not very effective. Therefore, the search for efficient, effective, less expensive, and environmentally-friendly ways to remove industrial dyes from water remains open. Methylene blue (MB) removal from aqueous solutions is studied using raw laterite soil as a low-cost adsorbent. The physico-chemical properties and surface area were determined. Effects of parameters such as contact time, laterite dosage, pH, and ionic salts on MB adsorption by raw laterite were examined. The results showed that the maximum removal efficiency of MB adsorption was observed at pH values above 10, after 60 min of contact time, and with an adsorbent (raw Laterite) dose of 1.00 g in 100mL of dye solution. Increasing the salt concentration decreased the absorption of dye from solution. Ionic salt media containing, CaCl₂ and KCl have shown maximum and minimum influence, respectively, on the adsorption of MB by raw laterite soil. At the optimum conditions, the experimental adsorption capacity of raw laterite was 2.930 mg/g. The experimental data fitted the pseudo-second order kinetic model (R² = 0.99). The Freundlich adsorption isotherm model (R² = 0.99) showed the best fit to the experimental adsorption data. According to the Freundlich isotherm model, the calculated adsorption capacity of raw laterite was 2.949 mg/g. Desorption studies with several solvents revealed that the adsorbent could successfully retain MB, up to 33.89%. Therefore, it can be considered that raw laterite soil is effective in removing MB from aqueous solutions.