Phosphoric acid-modified biochar enhances electrokinetic in situ leaching technology to remediate Pb²⁺ contaminated soil

The present study instead phosphoric acid-modified peanut shell biochar was prepared and applied to treat Pb2+ contaminated soil. Firstly, its adsorption performance was verified. A variety of methods were used to characterize the materials before and after modification. The specific surface area analysis showed that the specific surface area of the modified biochar increased from 1.9475 to 4.2742 m(2)/g, and the total pore volume increased while the mean aperture decreased. Scanning electron microscopy showed that the surface of the modified biochar became rougher and rougher as the concentration of phosphoric acid increased. Fourier transform infrared spectroscopy proves that resulting in the successful recombination of phosphoric acid groups on biochar. The results showed that the best effect was achieved when the ratio of phosphoric acid to peanut shell was 1:2. The adsorption conforms to pseudo-secondary kinetics and Langmuir adsorption isotherms. XRD results showed that Pb-5(PO4)(3)OH crystal peak was formed after phosphoric acid-modified peanut shell biochar adsorption of Pb2+, indicating that Pb2+ was precipitated on the surface of phosphoric acid-modified peanut shell biochar during adsorption. The quantitative determination of the adsorption mechanism showed that 66.12% of Pb2+ was immobilized by the formation of mineral precipitation. Later, phosphoric acid-modified peanut shell biochar was used to improve electrokinetic in-situ leaching remediation techniques to treat soil Pb2+. The results showed that the average removal rate of Pb2+ increased from 54.56 to 74.3%, and the lead content of weak acid leaching decreased from 14.09 to 2.83%. Residual lead increased from 10.12 to 15.79%.