Mass-transfer processes of toxic hexavalent chromium adsorption onto food waste adsorbent

Heavy metal pollution caused by industrial operations is a global environmental issue. Chromium, used in chrome plating, textile dyeing, wood preservation, and metal fnishing, is classifed as a highly toxic agent to humans and other living organisms. To minimize health risks, these contaminant should be removed from the aquatic ecosystem. In the present study, a bioadsorbant was fabricated from vegetable waste biomass : potato peels (PP) was tested for the adsorption of toxic hexavalent chromium [Cr(VI)] from simulated wastewater. Due to the health effects associated to Cr(VI) toxicity, it is mandatory to treat chromium-bearing wastewaters before disposal in to the environment to avoid consequent health problems. The research of cheaper, locally available and renewable materials as precursors for producing activated carbon with comparable functionalities to the commercial product. The purpose of this study is to highlight vegetable waste and to examine the efficiency of potato peels towards the removal of hexavalent chromium from aqueous solution. The physicochemical and textural characterization of the prepared adsorbent was accomplished by using available techniques. The influence of the operating parameters were investigated in batch mode. Eight bottles were used during the batch experiments under the following operating conditions: Mass of PP and PAC: 0.25 g to 1.5 g,time: 0-60mn, pH:2-12,initial concentration of Cr (VI) : 10-30mg/l, Temperature: 30 to 60°C. Adsorption kinetics was assessed by fitting the experimental data with the chosen kinetic models. The ability of potato peels to adsorb Cr(VI) ion was determined from the adsorption isotherms plots and the thermodynamic parameters were estimated. Furthermore, a comparison of the results obtained is carried out with commercial powdered activated carbon (PAC). The best removal efficiencies are obtained at pH of order 2 and 12 for PAC and PP respectively, an optimal mass of PP at 0,5 g and 1 g of PAC at 300 rpm. The most appropriate model is Langmuir model and the kinetics are the pseudo second order. The adsorption reaction is a chemisorption according to Elovich's model and the diffusion is extraparticle by Webber and Morris model. The results obtained from this study suggest that the adsorbent prepared from plant biomass could be an interesting low-cost adsorbent to remove chromium VI. Keywords: Chromate VI, bioadsorbent, adsorption, kinetic, isotherms