Interfacial adsorption facilitated arsenate immobilization in soil using biochar-supported nanoscale goethite

Abstract

As(V)-contaminated soil is a serious global environmental issue and As(V) immobilization is still a challenge. This study synthesizes and applies a high-performance biochar-supported nanoscale goethite (nGBC) to immobilize As(V) in soil, elucidating the interfacial mechanisms through various characterization methods and density functional theory calculations. nGBC was successfully synthesized at 600 °C for 2 h using 0.6 mol/L Fe³⁺, achieving a maximum adsorption capacity of 110.28 mg/g As(V). When the As(V) concentration in soil of 50 mg/g, the leaching As(V) concentration decreases to 0.0004 mg/L after 28 d remediation, which is lower than Class I groundwater quality limit. During the remediation, As(V) replaces hydroxyl groups on goethite, and forms stable bidentate binuclear complexes with surface iron. Consequently, nGBC transformed organic, carbonate, and exchangeable fractions into a more stable residue fraction. This study offers an effective material for stabilizing As(V)-contaminated soils and introduces a novel strategy for investigating the interfacial remediation mechanisms of heavy metal-contaminated soils.