ABSTRACT
102Over the last century, continued population growth and industrialization has resulted in the degradation of a variety of water ecosystems. Such pollution is primarily caused by the discharge of inadequately treated industrial and municipal wastewater. Hexavalent chromium is one such toxic heavy metal which is considered to be a major pollutant in wastewater. The critical parameters affecting the adsorption of Cr(VI) are investigated by using both sweet lime and orange peel powder. The adsorption of Cr(VI) is totally depend on parameters like pH, contact time, temperature, and initial adsorbate concentration. It was observed that the percentage of adsorption increased with the increase of agitation speed up to 180 rpm. The percentage of adsorption increased with increase in particle size from 75 to 180, whereas the uptake also increased. The increase in percentage of adsorption and uptake with increase in particle size might be attributed to the increase in specific surface area of the adsorbent. As the pH increased, a sharp decrease in percentage of adsorption was observed and maximum adsorption capacity is observed at pH 1.25.
The adsorption kinetic models are important in the process of removal of toxic heavy metals from the aquatic environment. The equilibrium adsorption isotherms are also analyzed by studying Langmuir and Freundlich adsorption isotherms. The Kinetic modeling is also done by pseudo first order and pseudo second order kinetic models. The different statistical errors such as sum of the square of the error (SSE), sum of the absolute error (SAE), and average relative error (ARE) are calculated. From error analysis and correlation coefficient (R 2), the best fit for kinetic model was observed for pseudo second order kinetic model. The scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) analysis are also done to study the physical parameters of adsorbents. From the result, it can be concluded that sweet lime peel powder is best adsorbent for removal of chromium from wastewater as compared to orange peel powder.
