The removal and adsorption mechanisms of free amino acid l-tryptophan from aqueous solution by biomass-based activated carbon by H3PO4 activation: regeneration study

The objective of this work is to examine the effectiveness of low cost material as adsorbent for the removal of free amino acid l-tryptophan from aqueous solutions in order to avoid the formation of undesirable disinfection by-products, trihalomethanes and iodinated trihalomethanes, during the water chlorination. The adsorbent was prepared from date pits and activated with H3PO4 (DPH). The textural properties of DPH were characterized by FT-IR spectroscopy, SEM analysis and N2 adsorption-desorption isotherms. DPH possesses a large specific surface area (1040 m2 g–1) and a high total pore volume (1.089 cm3 g–1). Batch adsorption experiments were investigated to examine the effects of contact time, initial concentration, temperature, ionic strength and pH on the l-tryptophan adsorption. Among three isotherm models, the Langmuir model gave a perfect fit for the experimental data of l-tryptophan with a maximum monolayer adsorption capacity of 144.93 mg g–1 on DPH. The functional groups on the DPH surface can attract the l-tryptophan via π–π hydrophobic interactions, dipole-dipole hydrogen bonding and n–π interactions. The thermodynamic parameters suggested that the l-tryptophan adsorption is spontaneous and exothermic with a physisorption process. After four cycles, the regeneration efficiency of the used DPH was about 59.9 %.Graphical abstract

Source: Physics and Chemistry of the Earth, Parts ABC - August 1, 2019 Category: Science Source Type: research