A new adsorbent (aluminum modified talc) for phosphate removal from alkaline solutions and optimization of data by central composite design

Abstract

A new adsorbent material, aluminum modified talc clay, was synthesized for phosphate adsorption from solutions. The raw talc and aluminum coagulation were not effective than modified talc. Due to this reason, phosphate adsorption from synthetic solutions on modified talc was investigated in a batch system as a function of pH, time, concentration, temperature, solid amount and aluminum loading effect. Optimum conditions for modified talc were determined as pH (11), temperature (40 degrees C), concentration (200 mg/L), time (20 min), solid amount (1 g/50 mL), and aluminum loading (1.5 g AlCl3/10 g talc/50 mL pure water). Optimization of phosphate adsorption onto modified talc was realized by central composite experimental design using Minitab 16.0 program. The statistically importance sequence of parameters were dosage, dosage-dosage, pH-dosage, pH, pH-pH, concentration, dosage-concentration, pH-concentration and concentration-concentration. The kinetics of removal obeyed the pseudo-second-order model rather than pseudo-first-order model. The isotherm data fitted well to the Langmuir isotherm. The thermodynamic analysis of phosphate adsorption indicated non-spontaneous and physical adsorption of phosphate. The rate controlling mechanism for adsorption was particle diffusion. The XRD analysis for raw talc was done. FTIR-ATR analysises for raw, modified and phosphate adsorbed modified talc were done. SEM images before and after adsorption was interpreted. According to obtained results, the modified talc was found as an effective adsorbent for phosphate removal from uncomplex wastewaters for control of eutrophication and for production of drinking water. Maximum phosphate capacity was calculated as 37.45 mg/g.