Kinetics, Isotherms, and Thermodynamic Modeling of the Adsorption of Phosphates from Model Wastewater Using Recycled Brick Waste

TLDR

Elevated phosphate concentrations in wastewater cause eutrophication, and their removal is essential, yet conventional chemical precipitation is costly and environmentally burdensome. This study evaluates recycled brick waste as an adsorbent for phosphate removal in wastewater treatment. Kinetic, isotherm, and thermodynamic analyses were performed to elucidate the adsorption mechanisms of phosphates onto brick particles. Adsorption capacity increased with contact time, dosage, and initial concentration, fitting pseudo‑second‑order kinetics and the Langmuir isotherm with a maximum capacity of 5.35 mg g⁻¹, and the process was exothermic, spontaneous, demonstrating bricks as a sustainable alternative.

Abstract

Phosphates in wastewater at elevated concentrations cause eutrophication of water bodies and their removal from treated wastewater is essential before effluents are discharged to the environment. Phosphates are predominately removed during wastewater treatment by chemical precipitation which is usually expensive and has a significant environmental footprint. The purpose of this study was to investigate the effectiveness of waste recycled bricks as adsorbent for phosphate removal during wastewater treatment. The kinetics, isotherms, and thermodynamics of adsorption were investigated to establish the mechanisms of adsorption. The results showed that adsorption capacities increased with an increase in contact time, adsorbent dosage, and initial phosphate concentration. The kinetic study indicated that adsorption was governed by several mechanisms with various processes dominating different stages of the adsorption. The adsorption process was better represented by the pseudo-second-order kinetics and the Langmuir isotherm adequately described the adsorption of phosphates onto brick particles with a maximum adsorption capacity of 5.35 mg/g. The thermodynamic studies showed that the adsorption process was exothermic and proceeded spontaneously, demonstrating that waste bricks can be used as a sustainable alternative for the effective removal of phosphates from wastewater.