Comparison on Copper (II) Desorption from Loess Soil with and without Biochars Derived from Flax and Rape Straws

It has been reported that biochar is capable of adsorbing and immobilizingheavy metals in soils due to its prominent properties, such as the porous structure,large and charged surface, and functional groups on surface. The desorption of Cu (II)(Cu) from loess soil was studied and compared using batch washing method, with andwithout biochars derived from flax and rape straws. The effects of contact time, initial pHvalue of solution, temperature, initial concentration of Cu in soil, and co-existing Ca2+ ondesorptions were investigated. The pseudo-second-order kinetic model could be usedto describe the desorbing process well. The leaching ability (η) of Cu from solid phaseincreased in overly acidic solutions. Increasing temperature improved desorption of Cufrom loess soil. When the initial concentration of Cu in soil increased, the η values ofCu decreased. Slight effect of Ca2+ on the η value of Cu was found. No significant immobilizationof Cu by biochars was found because loess soil is much capable of holdingCu, possibly due to high content of carbonates. The results could provide references forimmobilization remediation of loess soils contaminated with heavy metals using biocharsas amendment.