The effects of Cd on the growth and Cd uptaking in corn (Zea mays L.) were explored under different Cd stress. The results showed that no reduction in shoot and root dry matter yields were noted when the plants were grown at Cd supply levels ≤100 μmol l⁻¹ nutrient solution. The Cd concentration in the shoots and roots of corn increased sharply with increasing external Cd supply levels, peaked at 50 μmol l⁻¹, and then decreased slowly with further increasing Cd levels due to high Cd toxic effects on root growth. The concentrations of chlorophyll a, chlorophyll b and chlorophyll a + b in the leaf of corn decreased slowly with increasing external Cd supply levels. Proline concentrations of corn increased when the plants were grown under the external Cd influence. The lower concentration of Cd treatments did not influenced the growth of corn significantly, and increased the uptake of Cd, the higher levels of Cd supply caused significantly physiological resposes and decreased the Cd uptaking.

Soil heavy metal pollution has become an important environmental problem in the world. Therefore, it is particularly important to find effective remediation methods for heavy metal contaminated soil. Biochar (BC) is a kind of soil heavy metal passivator with a wide range of applications. It also has a good effect on the control of soil heavy metal pollution. However, BC does not have sufficient fixation capacity for para-anionic contaminants. Nano-zero-valent iron (nZVI) has a strong reducing ability, which can make up for this defect of BC. Therefore, to improve the passivation effect of heavy metals, nanomaterial modification is proposed to optimize biochar performance. Nanoparticles are used as carriers to impregnate biochar (BC). Biochar-supported nano-ferric zero-valent materials are prepared to repair soil contaminated by heavy metals. Results show that the physicochemical properties of modified biochar are significantly optimized. At 5%, the modified biochar (1:3) treatment group had the best remediation effect on Cd-contaminated soil, which significantly promoted soil catalase activity. The modified biochar (3:1) treatment group had the best remediation effect on As-contaminated soil, and significantly increased soil pH, Cation Exchange Capacity (CEC), and available Fe content. Modified biochar (1:3) with 3% added content was used to repair actual composite heavy metal contaminated soil, and the relative percentage content of Cu, Zn, As, Cd, and Pb residue state increased by 10.28%, 7.81%, 7.44%, 9.26%, and 12.75%, respectively. The effects of nZVI@BC on the remediation effect and soil enzymes of Cd- and As-contaminated soil under different factors such as mass ratio of carbon and iron and dosage were studied. The remediation mechanism of Cd- and As-contaminated soil was clarified, and a good solidification and stabilization effect was obtained. This provides a theoretical basis for nZVI@BC remediation of soil contaminated by Cd and As. It has good application value in the treatment and remediation of complex heavy metal contaminated soil.

The swelling behaviors and water retention of superabsorbent materials prepared from acrylic acid/acrylamide copolymer and acid-modified attapulgite under ultrasonic treatment and different pH conditions were investigated. The results demonstrated that a suitable amount of attapulgite can effectively improve the absorption capacity. The superabsorbent achieved the highest absorptions of 1257.54 g g⁻¹ and 209.45 g g⁻¹ in distilled water and a 0.9 wt% NaCl solution, and a higher water absorbency occurred over a wide pH range of 5–9 when the ultrasonic power was 200 W, and the attapulgite content was 10%. Addition of attapulgite could significantly increase the water absorption and retention of this kind of material, which can be applied as a sand-fixing material.