Current World Environment Vol. 10(1), 270-280 (2015) Performance of Laterite Soil Grains as Adsorbent in the Removal of Chromium I.J. SYAMA 1 , ARUN KUMAR THALLA 2 and D.S. MANU 3 * Department of Civil Engineering, National Institute of Technology Karnataka, Surathkal, Karnataka, India. http://dx.doi.org/10.12944/CWE.10.1.33 (Received: January 16, 2015; Accepted: February 20, 2015) ABSTRACT The present study aims to examine the efficiency of laterite grains (LG) and acid activated laterite grains (AALG) as an adsorbent for removal hexavalent chromium and ferric ion from synthetic wastewater, under laboratory conditions. Adsorption of hexavalent chromium and ferric ion from synthetic wastewater is examined by batch and column studies wherein it is found to be dependent on pH, Contact time, adsorbent dosage and initial adsorbate concentration. Percentage removal enhances with the increase in adsorbent dosage and with low pH, the optimal removal is achieved at pH=2. AALG is found to investigate possibility of improvement in removal efficiency of hexavalent chromium. The removal efficiency of AALG is found to be significantly higher than the efficiency obtained from LG, at pH=7. An adsorbent dosage 2g of LG is found to be optimum for removal of ferric ion with low initial concentration of 2.5 mg/L. The equilibrium adsorption data obtained from batch studies were fitted with Langmuir and freundlich isotherm for both hexavalent chromium and ferric ions. The percentage removal obtained from batch adsorption studies were found to be higher than that obtained by column studies for both the adsorbates. Key words: Adsorption, Laterite, Chromium, Isotherms. INTRODUCTION Since last 5 decades, environmental pollution due to rapid industrialization has created more modern problems. Industries have a large prospective to cause streams, river, lake and sea pollution, thereby causing increased addition of heavy metals into the environment (Sahu et al. 2009). Environment pollution by toxic heavy metals occurs through industrial, military and agricultural processes (Ajmal, Ali Khan Rao, and Siddiqui 1996).A serious threat that posed to the environment due to the discharge of heavy metals into the streams there by causing accumulation leading to adulteration of food chain . Toxicity is caused due to the presence of heavy metals like Ni, Zn, Cu, Cd, Cr, and Hg are toxic even in trace amounts. Metal species produced due to the various activities, when released into the environment they increase persistently (Chand, Agarwal, and Kumar 1994). It is a mandate to monitor their levels within permissible limits as recommended by the World Health Organization (WHO) in drinking water, wastewater and water used for farming and recreational uses. Cr (VI) and Cr (III) are the two stable oxidation states of chromium. The Cr (VI) state is of especial interest because of its noxious. Thermodynamically stable chromate (CrO 4 2- ) and dichromate (Cr 2 O 7 2- ) anions which vary over a wide pH range are the usual hexavalent chromium wastes discharged into the surroundings. Cr (VI) compounds are noxious which causes lung cancer, as well as kidney, liver and skin damage in human beings (Kousalya, Gandhi, and Meenakshi 2010). As per Indian standards the acceptable limit of Cr (VI) that is to be discharged from industrial effluents to surface water is 0.1 mg\L. The maximum acceptable limit of the chromium content in drinking water is 0.05 mg/L. Various treatment skills have been developed