Heated laterite as a low-cost adsorbent for arsenic removal from aqueous solution

Existing works reported that the laterite prepared using chemical treatment improved its removal performance compared to the raw laterite. However, this treatment has several drawbacks such as costly and potentially produces pollutant. To overcome this issue, the present work proposed heated laterite (HL) for removal of Arsenic (III) (As(III)) from aqueous solution as a low-cost adsorbent without any chemical use. HL was firstly obtained via the heat treatment a temperature of 550 oC for raw material with geometric sizes of 0.6 to 1.0 mm. Properties of HL in terms of surface morphology, energy dispersive X-ray, porosity, surface area, and Fourier transform infrared spectroscopy were then characterized. Effects of physicochemical parameters such as pH, agitation speed, adsorbent dosage, and initial concentration for optimal adsorption performance of As(III) were investigated. Gibbs free energy, enthalpy, and entropy of the adsorption were also determined, from which the sorption capacity and isotherm were estimated using Langmuir and Freundlich isotherm models. Langmuir model was found to be more reliable than Freundlich in describing the process behavior. This study found that the removal performance of HL was strongly affected by the physicochemical parameters. As the main finding, the optimal conditions for a low-cost and green adsorbent were adsorbent dose of 6 g L-1, with an initial As(III) concentration of 0.5 mg L-1, pH 7, and agitation speed of 250 rpm, which successfully removed 98.8% of As(III)