Ozone and Ammonium Hydroxide Modification of Biochar Prepared from Pisum sativum Peels Improves the Adsorption of Copper (II) from an Aqueous Medium

This study evaluated the effectiveness of unmodified and modified biochar derived from Pisum sativum peels waste biomass as an adsorbent of copper (II) from aqueous medium under batch adsorption experiments at room temperature. The unmodified biochar was chemically modified by ozone oxidation followed by reaction with ammonium hydroxide and labeled as Pea-B and Pea-BO-NH2. The adsorption behavior of Cu2+ ions and the effect of required experimental parameters as initial Cu2+ ions concentrations, biochar dose, reaction time, and pH were intensively studied. The unmodified biochar (Pea-B) and modified biochar (Pea-BO-NH2) had significant copper (II) adsorption capacities of 126.25 and 156.25 mg/g, respectively, with 100% removal efficiency. The prepared biochars were characterized by Brunauer, Emmett and Teller (BET), Barrett, Joyner, Halenda (BJH), Scan Electron Microscope (SEM), Fourier Transform Infrared (FTIR), Thermal gravimetrical analysis (TGA) and Energy Dispersive Spectroscopy (EDAX) analyses. EDAX and FTIR analyses proved that amino groups were successfully formed onto the modified biochar surface. The data of adsorption experiments at equilibrium were studied by using various isotherm models as well as the error function equations were applied to the data of isotherm models. The analysis of the experimental data of Pea-B and Pea-BO-NH2 biochars showed that the best fit isotherm models were the Langmuir and Tempkin isotherm models, respectively. The adsorption rate of copper (II) was analyzed using different kinetic models and the pseudo-second-order was expressed as the most appropriate model for both Pea-B and Pea-BO-NH2 biochars.