Thesis Abstract

The effects of the operating parameters such as in fluent Cr(VI) concentration, pH, biomass concentration, flow rate and temperature, on the Cr(VI) removal were investigated in the continuous system using a packed-bed reactor. Percentage removal curves were obtained for different flow rate, pH, temperature, biomass concentration and initial concentration of Cr(VI). It was found that the adsorption of Cr(VI) to the biomass was strongly dependent on these parameters, as expected. In particular, the in fluent pH and temperature were most significantly affected leading toa high percentage removal of Cr(VI); a decrease in the influent pH of 2, and an increase in the temperature up to 70°C enhanced the Cr(VI) reduction in the column significantly.Both Langmuir and Freundlich adsorption isotherms fitted reasonably well withthe data and showed high correlation coefficient (R2) values of 0.993 and 0.985 respectively. These results show that, the adsorbent can be used as a low cost alternative in biosorption of wastewaters containing lowerconcentrations of Cr(VI).Finally, the potential of the column packed with corncobbiomass for Cr(VI) detoxification has been found to be a good biosorbent in removal of Cr(VI) from aqueous solutions and also in the treatment of Cr(VI) containing industrial waste.

Thesis Overview

1.0 INTRODUCTIONOver the last three decades there has been increasing global concern over the public health impacts attributed to environmental pollution. The World Health Organization (WHO)estimates that about a quarter of the diseases facing mankind today occur due to prolonged exposure to environmental pollution (WHO, 2002).Pollution by heavy metals is one of the serious environmental threats as a result of various industrial discharges (Wang and Chen, 2009). Hexavalent chromium Cr (VI) is released into the environment by many industrial activities such as leather tanning, chrome plating, stainless steel welding, pigment production and nuclear weapon production (Gonzalez et al., 2003). Chromium exists in two oxidation states Cr(III) and Cr(VI), and the most toxic form is Cr(VI), which has been implicated in causation of liver damage, pulmonary congestion and oedema (Babu and Gupta, 2008; Raji and Anirudhan, 1998).Pollution of water due to presence of certain heavy metal ions is a severe socio-environmental problem caused by the discharge of industrial wastewater.