Sorption Studies on the Remediation of Cadmium (II) Ions Contaminated Water Using Succinic Acid Modified Red Onion Skin Extract

Abstract

Batch experiments were conducted for the removal of cadmium (II) ions from synthetic wastewater using succinic acid modified red onion skin extract (SROSE). Effects of pH, initial metal ion concentration and contact time were investigated. Maximum metal removal for cadmium was observed at pH 6.2, initial metal ion concentration of 20 mg/L, 28^oC temperature and 50 min. contact time. The experimental data were analyzed based on Freundlich, Langmuir, Temkin and Flory-Huggins adsorption isotherms; and the results obtained from the correlation coefficients of the plots indicated that Freundlich adsorption isotherm gives the best fit for the experimental data. The thermodynamic parameters were calculated and the results obtained indicated that the sorption process was spontaneous and exothermic.  The likely mechanism responsible for the Cd (II) ions removal was analyzed using the Dubinin-Radushkevich (DR) isotherm at different temperatures, and the results obtained showed that the major sorption mechanism was particle diffusion. Kinetic studies revealed that the adsorption of metal ions followed a pseudo-second order reaction.