Immobilized microbial technology has recently emerged as a prominent research focus for the remediation of heavy metal pollution because of its superior treatment efficiency, ease of operation, environmental friendliness, and cost-effectiveness. This study investigated the adsorption characteristics and mechanisms of Cd²⁺ solutions by Lactobacillus plantarum adsorbed immobilized on distiller’s grains biochar (XIM) and Lactobacillus plantarum–encapsulated immobilized on distiller’s grains biochar (BIM). The findings reveal that the maximum adsorption capacity and efficiency were achieved at a pH solution of 6.0. Specifically, at an adsorption equilibrium concentration of cadmium at 60 mg/L, XIM and BIM had adsorption capacities of 8.40 ± 0.30 mg/g and 12.23 ± 0.05 mg/g, respectively. BIM demonstrated noticeably greater adsorption capacities than XIM at various cadmium solution concentrations. A combination of isothermal adsorption modeling, kinetic modeling, scanning electron microscopy–energy dispersive X-ray spectroscopy, X-ray diffractometer (XRD), and Fourier-transform infrared spectroscopy (FTIR) analyses showed that cadmium adsorption by XIM primarily involved physical adsorption and pore retention. In contrast, the adsorption mechanism of BIM was mainly attributed to the formation of Cd(CN)₂ crystals.

[Objective] To assess the bioremediation potential of garbage enzymes in heavy metal-contaminated lead-zinc mine soils. [Method] A pot experiment evaluated garbage enzymes application effects on: (1) Pb/Zn/Cd bioavailability and phytoavailability, (2) soil fertility parameters, (3) soil enzyme activities, and (4) physiological responses of Chinese cabbage. [Results] Garbage enzymes significantly reduced heavy metal bioavailability, decreasing leaf Pb/Zn/Cd concentrations by 66.8%/17.6%/37.4% and root levels by 34.3%/23.4%/46.8% versus controls. Soil fertility improved substantially, with available N/P/K increments of 2.43–31.2%, 1.86–45.5%, and 3.40–22.3%, respectively. Key soil enzymes (urease, sucrase, catalase, phosphatase) exhibited enhanced activities. Garbage enzymes treated plants showed increased biomass (fresh weight), chlorophyll (21.8%), and soluble sugars, alongside reduced stress markers: nitrate-N (-24.3%), malondialdehyde (-33.6%), proline (-18.9%), and superoxide dismutase (-42.1%). [Conclusions] Garbage enzymes demonstrate dual functionality in metal immobilization and soil revitalization, offering an eco-sustainable solution for restoring agricultural productivity in contaminated ecosystems.

Soil contamination with heavy metals is a significant environmental issue that adversely affects plant growth and agricultural productivity. Biochar and microbial inoculants have emerged as a promising approach to solving this problem, and previous studies have focused more on the remediation effects of single types of materials on heavy metal soil pollution. This study examined the impact of both standalone and combined applications of distiller’s grains biochar, Lactobacillus plantarum thallus, and the bacterial supernatant on the availability of cadmium (Cd), lead (Pb), and zinc (Zn) in soil, its physicochemical features, and its enzyme activities; this study also examined the growth, physiological and biochemical characteristics, and heavy metal accumulation of Sorghum-sudangrass. The findings suggest that the application of distiller’s grains biochar, Lactobacillus plantarum thallus, and the bacterial supernatant can improve the soil’s physical and chemical properties and enhance soil enzyme activity while reducing the availability of heavy metals in the soil. Furthermore, the addition of these materials promoted plant growth, increased stress resistance, and significantly decreased the accumulation of heavy metals in the plants. A thorough analysis of the results shows that applying 0.025% Lactobacillus plantarum thallus along with 4.4% distiller’s grains biochar produced the best results.

Pb²⁺ and Cd²⁺ represent common heavy metal contaminants in aquatic environments, posing significant risks to ecosystem stability and human health. To develop efficient adsorbents for removing Cd²⁺ and Pb²⁺ while achieving resource utilization of industrial by-products (red mud and distiller’s grains), this study synthesized a novel composite biochar—red mud–Lactobacillus plantarum composite biochar (RM)—by immobilizing red mud and Lactobacillus plantarum onto biochar derived from distiller’s grains. The structural and chemical properties of RM were characterized using SEM-EDS, XRD, and FTIR. Batch adsorption experiments were conducted to evaluate the effects of various experimental factors on Cd²⁺ and Pb²⁺ adsorption. The adsorption process was further elucidated through kinetic and isothermal models, revealing that it follows the pseudo-second-order kinetic model. Equilibrium data were best described by the Langmuir model for Cd²⁺ and the Freundlich model for Pb²⁺. The maximum adsorption capacities reached 12.13 mg/g for Cd²⁺ and 130.10 mg/g for Pb²⁺. The primary mechanisms involved in Cd²⁺ and Pb²⁺ adsorption by RM include surface complexation, cation–π interactions, ion exchange, and coprecipitation. These findings demonstrate that RM represents a promising and effective adsorbent for the remediation of heavy metal-contaminated water.

The heavy metals in a zinc smelting waste dump area, northwest of Guizhou Province Henan, were investigated, and the subsequent evaluation of the pollution characteristics and health risks was conducted in the present study. The results indicated that the average levels of Cd, Pb, and Zn in slag and its surrounding soil significantly exceeded the soil background values in Guizhou Province and the values specified in the Soil Environmental Quality Risk Control Standard for Soil Contamination of Agricultural Land. The total non-carcinogenic risk values for children and adults, resulting from various heavy metals in waste slag through multiple exposure routes, were found to be 28.89 and 16.81 times higher than the acceptable level of 1, respectively, with Pb contributing to most of the risks. The integrated pollution index mean values for all crops exceeded the threshold value of 3.0 for heavy pollution, indicating that consuming crops from the study area posed significant risks to the general population. It was also noted that the potential health risks of heavy metals for children were higher than for adults. The heavy metal contents in soil and corn decreased with increasing distance from the slag heap, consuming corn grown on farmland 150 meters from the slag heap still posed health risks to humans.