Strength characteristics and microscopic mechanism of activated MgO-modified biochar carbonization curing Zn2+ polluted soil

Abstract

Conventional curing agents are associated with environmental impacts when treating Zn²⁺contaminated soils. To overcome this limitation. In this study, we study a new type of MgO-CSB curing agent. Namely, corn stover biochar is modified with activated MgO. Modification of corn stover biochar using activated MgO, and carbonation curing was adopted to solidify/stabilize the Zn²⁺contaminated soil. The curing efficacy of Zn²⁺contaminated soil under modified mass ratio, Zn²⁺ concentration, carbonation time, and curing agent incorporation was investigated. The findings indicate that the optimal adsorption efficiency was attained following the co-pyrolytic modification of activated MgO with corn stover biochar at 700°C. The optimal modified mass ratios for curing were found to be 1:1, 1:2, and 2:1 at Zn²⁺ concentrations of 0.1 %, 0.5 %, and 1 %, respectively. At a lower Zn²⁺ concentration, peak carbonization intensity is achieved at 0.5 hours, while at a 1 % Zn²⁺ concentration, peak intensity is reached at 1 hour. The deformation modulus of the cured soil increases as the curing agent dosage increases and the soil aggregates become denser. SEM results show that: The carbonization and curing reaction products are mainly nesquehonite and Mg (OH)₂. The internal structural damage of the cured soil was aggravated by the increase in Zn²⁺concentration, and the generation of nesquehonite and Mg (OH)₂ was inhibited; The carbonation time was extended to 1 h and the soil structure stability was enhanced.