Comparative evaluation of phosphate abatement using laterite soil and activated carbon

Abstract

Abstract: The present study aims to evaluate and compare the suitability of thermally activated laterite soil (TAL) and activated carbon (AC) as adsorbents in the abatement of phosphates (PO<inf>4</inf> 3?) from synthetic wastewater. The AC was derived from the wasted sludge of an activated sludge process by subjecting it to an activation temperature of 600 °C. The impregnation ratio of 1 (sewage sludge): 1 (KOH) was used for the present study. The soil and wasted sludge were characterized to determine the constituents, and the adsorbents were prepared by thermal and chemical activation, respectively. The AC exhibited a maximum iodine number of 837.51 mg/g using KOH as an activating agent. Batch and column studies were conducted to determine the dependency on pH, contact time, adsorbent dosage and initial PO<inf>4</inf> 3? concentration. An optimum PO<inf>4</inf> 3? removal using TAL and AC was achieved around pH 6. The removal efficiency of AC was found to be slightly higher than the efficiency obtained from TAL. The percentage removal of PO<inf>4</inf> 3? obtained from batch adsorption studies was found to be higher than that obtained by column studies. The equilibrium adsorption data from batch studies were attempted to fit with linear, Langmuir and Freundlich isotherm models. Residual and least square analysis confirms the Freundlich isotherm to be the best fit. Graphical abstract: [Figure not available: see fulltext.] © 2018, Islamic Azad University (IAU).