Arsenic adsorption from groundwater using non-toxic waste as adsorbent (original) (raw)

DESALINATION AND WATER TREATMENT

Millions of people in the world are exposed to arsenic-contaminated groundwater. To decrease the concentration of arsenic in water, adsorption of arsenic was performed on a simple and easily available material, that is, eggshell. Powdered eggshell (ES) was prepared and was characterized by using Brunauer-Emmett-Teller, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy, and energy-dispersive X-ray spectroscopy (EDX). It was revealed from FTIR and EDX that the presence of CaCO 3 in ES is the major reason for arsenic adsorption. Removal of As(III) and As(V) as a function of the adsorbent dose, pH, contact time, and agitation speed were studied. The adsorption capacity is strongly influenced by the pH of the solution. ES removed 68.54% of As(III) and 72.01% of As(V) under optimum conditions from 2 mg/L As(III) and As(V) solutions. ES was also carbonized at 700°C, and it could remove 70.09% of As(III) and 76.44% of As(V) under similar conditions. Adsorption isotherms and kinetics were determined for As(III) and As(V). As(III) adsorption followed the Langmuir isotherm, revealing monolayer adsorption. As(V) adsorption followed the Freundlich isotherm, revealing multilayer adsorption. Similarly, adsorption of As(III) and As(V) on carbonized eggshell followed pseudo-second-order kinetics and on ES followed Elovich kinetics, both suggesting that the adsorption process is a chemisorption process. Also, the study of the intraparticle diffusion model concluded that there was surface adsorption along with an intraparticle diffusion mechanism during the adsorption of arsenic. The best isotherm and kinetic models were selected, based on the error values using the chi-square test, root mean square error, and average percentage error.