Fe-loaded biochar obtained from food waste for enhanced phosphate adsorption and its adsorption mechanism study via spectroscopic and experimental approach

The re-utilization of food waste is an eco-friendly method for valorizing waste. In this study, food waste was blended with iron (Fe-FW) and optimized using the response surface methodology (RSM) to produce Fe-loaded food waste biochar (Fe-FWB); moreover, the waste was utilized to probe the adsorption of phosphate in water, where pyrolysis time (1.0, 2.5, and 4.0 h), temperature (300, 450, and 600 degrees C), and Fe concentrations (0.1, 0.3, and 0.5 M) were set as independent variables. After optimizing the Fe-FWB, batch experiments were performed to examine the phosphate sorption characteristics of Fe-FW and Fe-FWB. A pseudo-second order and Elovich kinetic model thoroughly explained the adsorption kinetics, which was indicative of the rate-limited sorption via diffusion or surface coverage after the rapid initial adsorption. The Freundlich and Redlich-Peterson isotherm models more accurately simulated the adsorption of phosphate onto Fe-FW and Fe-FWB than the Langmuir isotherm model. The thermodynamic results presented a positive value of Delta G(0), clearly indicating that the reaction was not spontaneous; positive values of Delta H-0 and Delta S-0 affirmed the endothermic characteristic of phosphate uptake into Fe-FW and Fe-FWB, with an increase in randomness. The adsorption of phosphate onto Fe-FW and Fe-FWB decreased as the solution pH increased from 3 to 11. In the presence of interfering anions, phosphate adsorption onto Fe-FWB was influenced by the coexistence of HCO3-, SO42-, and NO3-. These results suggest that the synthesized Fe-loaded food waste biochar can be used as an emerging adsorbent for phosphate removal from aqueous solutions.

Automated summary

The study optimized the production of Fe-loaded food waste biochar by blending food waste with iron and investigated its adsorption of phosphate in water. The synthesized Fe-loaded food waste biochar showed potential as an effective adsorbent for phosphate removal from aqueous solutions.