SELECTING OF AN EFFECTIVE ADSORBENT FOR TREATING PHOSPHATE CONTAMINATION

Abstract

Experimental research on the adsorptive capacity of Granular Activated Carbon GAC, Phosphate Rock PR, Saw Dust SD and Rice Husk RH for phosphate removal from simulated wastewater was conducted. Results showed that the removal efficiency of four adsorbents was the consequence of RR (82.6%) ˃ SD (43.72%) ˃ GAC (41.28%) ˃ RH (34.4%). To understand the action of phosphate uptake, factors influencing the adsorption process using the best adsorbent (PR) including pH, mixing speed, contact time, the weight of the adsorbent, initial phosphate concentration, and temperature were investigated. It was found that the equilibrium data fitted very well with the Langmuir model with a high determination coefficient (R2). The maximum uptake capacity (qmax) was 24.716 mg/g. Adsorption data were modeled using the pseudo-first, pseudo-second-order, Intraparticle diffusion, and Elovich models. It was found that the pseudo-second-order kinetic equation could best describe the adsorption kinetics. Thermodynamic parameters showed that the adsorption of investigated phosphate onto PR was exothermic, spontaneous in nature and the process is physisorption. It was found that sodium hydroxide (0.1 M NaOH) was an efficient adsorbent solution in the recovery of phosphate pollutants among different adsorbents: HCl, H2SO4, NaOH, Na2CO3, EDTA, and deionized distilled water (DDW) from PR. The breakthrough curves for the adsorption column test were obtained in a continuous adsorption fixed-bed experiment, The measured breakthrough times for RH, GAC, SD, and PR were found to be 10, 30, 40, and 60 min, respectively.