Résumé:
This research was aimed to further evaluate the potential of biosorption technique by exploiting locally available biosorbents undergoing minimum pretreatment steps. The toxic metal of interest for biosorption in this work is boron and biosorbents selected were wool and date pits powder as an agro-waste. Characteristics of the adsorbent were established using Fourier Transform Infrared spectroscopy (FTIR) and Brunauer–Emmett–Teller (BET) surface area. Batch adsorption experiments were performed to assess performances and process mechanisms. For DPP, with increasing pH, the adsorption efficiency progressively increases, becomes optimal in the pH zone 6 to 9 and then drastically decreases. The adsorption equilibrium was attained after 90 minutes and the experimental data were well described by Dubinin– Radushkevich and Tempkin adsorption isotherms. The boron adsorption process followed Elovich and pseudo-second order kinetic models and appeared to be controlled by both intraparticle diffusion and liquid film mass transfer. FTIR spectroscopy evidenced that hydroxyl groups are the primary active sites involved in binding of boron species. The kinetic and equilibrium studies show that DPP has considerable potential for the removal of boron from aqueous solution. This agricultural byproduct may be an eco-friendly material and cost effective alternative to more costly chemical sorbents. For woll, batch sorption studies revealed that pseudo-second order and Langmuir isotherm models were suitable to describe the metals sorption kinetics and equilibrium, respectively. Process optimization helped to evaluate the simultaneous effects of pH, initial metal concentration, biomass dose and temperature. Characterization of metal-biomass interactions responsible for biosorption was studied employing FT-IR. The results suggested the involvement of electrostatic interactions, ion exchange and a weak surface binding in adsorption of boron by the selected biosorbent. Research conducted in this thesis can be of value to industries searching for efficient, simple, and green alternative metal treatment methods to meet the regulatory limits for the boron discharges at a lower cost.
