Preparation of modified-biochar from Laminaria japonica: Simultaneous optimization of aluminum electrode-based electro-modification and pyrolysis processes and its application for phosphate removal

• Electro-modification and pyrolysis processes were modeled and optimized using RSM.
• Quadratic regression model was accurately developed for phosphate adsorption.
• Physically and chemically modified-biochar (SOEM-biochar) was successfully prepared.
• Pseudo-second-order and Sips models fit the adsorption data of the SOEM-biochar.
• Maximum phosphate adsorption capacity of SOEM-biochar was 460.3 mg/g.

The preparation conditions of electro-modification (current density) and pyrolysis (pyrolysis temperature and heating rate) processes were simultaneously optimized using response surface methodology with the quadratic regression model associated with Box–Behnken design. By numerical optimization, the phosphate adsorption capacity of 245.06 mg/g was achieved, corresponding to 99.9% of the predicted values under statistically optimized conditions (current density: 38.78 mA/cm2, pyrolysis temperature: 584.1 °C, heating rate: 6.91 °C/min). By considering R2 and three error functions values, the experimental results of adsorption kinetics, and the equilibrium isotherms at different temperatures (10–30 °C) showed that predictive pseudo-second-order and Sips isotherm models could adequately interpret the phosphate adsorption process for ‘statistically optimized electrically modified’-biochar (SOEM-biochar). The maximum phosphate adsorption capacities of SOEM-biochar were found to be 273.9, 345.1, and 460.3 mg/g at 10, 20, and 30 °C, respectively, which are higher than that of other adsorbents reported in the literature.

Figure optionsDownload as PowerPoint slide