Nutrient removal from wastewaters using treated incineration residues of expired medications: Kinetics, thermodynamics and isotherm modeling

ABSTRACT

Incineration residues of expired medications (IREMs) were chemically treated (IREM-T) by a combination of mixed salts (CaCl₂, MgCl₂) and thermal treatments with NaOH. They were characterized and used for simultaneous ammonia and phosphates adsorption from wastewater. Batch experiments were carried out to investigate the effect of contact time, adsorbent dose, initial concentration, pH and temperature. The maximum adsorption capacity for phosphate and ammonium on IREM-T was found to be 24.68 and 34.30 mg g⁻¹, respectively, at the same initial concentration of 50 mg L⁻¹ on 5 g L⁻¹ of IREM-T. Langmuir, Freundlich, Temkin and Dubinin–Radushkevich adsorption models were applied to analyze the adsorption data. The equilibrium data fitted well with the Langmuir isotherm. To examine the adsorption mechanism, pseudo-first-order, pseudo-second-order and intraparticle diffusion models were applied to analyze the experimental data. All the linear correlation coefficients of the second-order model were found to be statistically significant, indicating the applicability of this kinetic equation to the adsorption of both phosphate and ammonium ions. This study revealed that IREM-T has the potential to be an efficient adsorbent for simultaneous nutrient removal. The effectiveness of this material was evaluated by applying this process to Algiers urban wastewater.

GRAPHICAL ABSTRACT

KEYWORDS:

• Adsorption
• ammonium
• incineration residues
• phosphate
• wastewater