Adsorption of hexavalent chromium from aqueous solutions using Canadian peat and coconut fiber

Abstract

Chromium compounds widely used in chemical processes are one of the biggest hazardous pollutants in industry effluents. The aim of the research is to investigate the role of the organic matter - Canadian Peat and coconut fiber in the removal processes of toxic chromium compounds from aqueous solutions. Characterization of organic matter has been carried out using scanning electron microscope with EDS, X-ray diffraction, Fourier transform infrared spectroscopy and BET measurements in order to analyze the surface and the porosity of the materials. In the study different concentrations of Cr have been investigated on the adsorption process and it has been found that maximum removal approximately 94% for coconut fiber and 91% for Canadian peat can be achieved in the lowest concentration equal to 25mg/dm3 after 72h. Langmuir, Freundlich and Temkin adsorption isotherm models have been used in order to describe the sorption parameters using the experimental data. Pseudo first, second order and Webber-Morris kinetics models have been verified to check the nature (chemical, physical) of Cr(VI) sorption on the materials. It has been found that pseudo-second order is the best fit for the adsorption what suggest that the process is of chemical nature. Regeneration of organic matter has been carried out by washing it with different eluents. Sodium citrate has the highest degree of chromium ions elution (53–65%). The removal efficiency was maintained for both materials after the elution process. Obtained results show that both organic materials can be effectively used for the removal of toxic chromium compounds from the aqueous solutions.