Kinetics Of Adsorption Of Arsenic Onto The Surface Of Goethite And Oxidation Of Arsenic In Homogeneous Aqueous Solution

Arsenic contamination of the water environment will greatly endanger human health, and the adsorption of arsenate and arsenite oxidation can significantly reduce the bioavailability of arsenic. The purpose of this article is to investigate mechanism of adsorption kinetics of arsenate and oxidation kinetics of arsenite by the research into influence of various factors on the adsorption rate of sodium arsenate onto goethite surface and the oxidation rate of sodium arsenite in homogeneous aqueous solution, so as to provide a theoretical basis for revealing the migration and transformation rules of arsenic in water environment.Firstly, article measured the adsorbance of sodium arsenate on the goethite surface under different time using single factor method in the case of static adsorption and plotted the kinetic curve. Then studying the influence of mixing intensity,initial sodium arsenate concentration pH and adsorbent particle size on the adsorption rate respectively and analyzing kinetic mechanism through Weber-Morris pore diffusion model. It was found that pseudo-2nd-order kinetic model could better describe the dynamic process of adsorption. Mixing intensity increased from 0 rpm to 210 rpm, adsorption rate constant increased by 20%. Initial sodium arsenate concentration decreased from 5mg/L to 3mg/L, adsorption rate constant increased by 157%. pH decreased from 7.4 to 2.2, adsorption rate constant increased by 17%. Adsorbent particle size decreased from 80-150 mesh to 300-500 mesh, adsorption rate constant increased by 23%. In addition, the influence of initial concentration on external and internal diffusion rate was much greater than mixing intensity,pH and adsorbent particle size.Article measured oxidation kinetic curve of sodium arsenite concentration versus time in homogeneous aqueous solution using single factor method and studied the influence of temperature,initial sodium arsenite concentration and pH on the oxidation rate respectively. Finally, the reason of the impact was analyzed. It was found that 1st-order dynamic model could better describe the kinetics of oxidation. Temperature increased from 15℃to 35℃, oxidation rate constant increased by 11.3%. Initial sodium arsenite concentration increased from 500μg/L to 2000μg/L, oxidation rate constant increased by 50.7%. pH increased from 5.6 to 9.8, oxidation rate constant increased by 11.8%. The influence of initial concentration on oxidation rate was greater than temperature and pH.