Performance And Mechanism Of Phosphate Adsorption From Wastewater On Modificated Palygorskite

In this paper, natural palygorskite clay were modificated by means of acid treatment and heat treatment by means of modified attapulgite clay. Modified materials and adsorption products were characterized and analyzed by XRD and XPS. Adsorption of low concentrations of phosphate on modified palygorskite clay was investigated through various static and dynamic experiments. The thermodynamics, kinetics and mechanism of modified palygorskite clay on phosphate adsorption were investigated.Best modified conditions of palygorskite clay is that solid-liquid ratio of palygorskite and hydrochloric acid is 1:3, and temperature of heating treatment is 600-700℃. Through XRD and XPS analysis, most of dolomite in palygorskite clay were removed in the acid treatment process. Doping and other chemical reactions happen between residual dolomite and palygorskite to form new material compositions MgO and Ca2SiO4 in the follow-up heating treatment process.Adsorption of phosphate on modificated palygorskite was affected by Reaction temperature, reaction time, initial concentration of phosphate and solid -liquid ratio, but the impact was slight. It was showed that adaptability of phosphate adsorption by modified palygorskite clay on the water quality was very good under certain conditions. The optimum parameters under the experimental conditions was that when the initial concentration of phosphate was 1 mg / L, solid to liquid ratio was 2 g / L, shock speed was 180r/min, and reaction time was 2h at room temperature, the removal efficiency of phosphate adsorption on modified palygorskite clay was close to 100%.Under the concentration and temperature range of this study, Adsorption isotherms of modified palygorskite clay fitted to Langmuir isotherms equation. It is showed that the adsorption process belongs to monolayer surface adsorption. The separation characteristics factor RL is 0 0,△G <0,△S >0, and the△G values were between -21.46~-30.46 KJ·mol-1, the phosphate adsorption on modified palygorskite clay was spontaneous, endothermic and the coexistence of physical adsorption and chemical adsorption. Adsorption of low concentrations of phosphate on modified palygorskite clay fitted to uasi-second order kinetic equation; the apparent activation energy of phosphate adsorption was 18.58 KJ ? mol-1. It indicates that the adsorption was joint controlled by film diffusion and chemical adsorption. Thermodynamics and kinetics study also showed that adsorption of low concentration of phosphorus on modified palygorskite clay is the coexistence of physical adsorption and chemical adsorption process.