KINETICS AND ADSORPTION EFFICIENCY OF AMBO SANDSTONE FOR THE REMOVAL OF HEAVY METALS (Cr And Ni) FROM AQUEOUS SOLUTION

Abstract

In developing countries, most of the industries such as electroplating, textile, fertilizer, batteries, leather, and others discharge large amount of untreated wastewater into water bodies. This untreated water contains toxic heavy metals. There are many techniques for removing toxic chemicals from wastewater such as membrane filtration, ion exchange, and adsorption and coagulation methods. However, the adsorption method is most commonly used due to its cost-effective, efficient, simple and easy to operate, and environmentally friendly according to many studies. The aim of this study was to assess the adsorption efficiency of Ambo sandstone for the removal of Cr and Ni from aqueous solution. The various parameters investigated in this study included pH, dose of adsorbent, agitation speed, contact time, size of adsorbent and initial metal ions concentration. Adsorption isotherm and kinetics studies were also studied. The results indicated that optimum conditions for Cr(VI) and Ni(II) adsorption were at pH 7 and 9, dosage 0.75 g and 1.5 g, agitation speed 160 and 120 rpm, contact time 12 and 15 h and initial concentration 10 and 30 mg/L, respectively. Different particle size also used for these adsorption and small size particle has high parentage of removal efficiency for Cr (85) and Ni (95.2). The adsorption equilibrium data correlate well with Freundlich model for Cr(VI) (R2 = 0.999) and Ni(II) (R2 = 0.93). Kinetic data correlated well with the pseudo-first order for Cr and pseudo-second order for Ni. The maximum adsorption capacity (qmax) of Ambo sandstone was found to be 1.02 mg/g for Cr(VI) and 1.79 mg/g for Ni(II). Therefore, it is recommended that Ambo sandstone can be used, as a low cost and abundant source for the removal of heavy metals as an alternative to more costly materials.