Zhu, et al (2024) Adsorption of Cd²⁺ by Lactobacillus plantarumImmobilized on Distiller’s Grains BiocharBiochar is a carbon-rich material created from biomass decomposition in low-oxygen conditions. It has important applications in environmental remediation, soil improvement, agriculture, carbon sequestration, energy storage, and sustainable materials, promoting efficiency and reducing waste in various contexts while addressing climate change challenges. More: Mechanism and Action. Microorganisms. https://doi.org/10.3390/microorganisms12071406

Cadmium (Cd) is a highly toxic heavy metal with severe environmental and health impacts. Its presence in industrial wastewater poses a significant threat to both human health and wildlife. Recent research focuses on innovative methods for removing heavy metals from wastewater, with immobilized microbial technology emerging as a promising solution due to its efficiency, environmental friendliness, and cost-effectiveness. This blog post explores a study that investigates the adsorption characteristics and mechanisms of cadmium removal using Lactobacillus plantarum immobilized on distiller’s grains biochar.

The study utilized two types of immobilized bacterial biochar: Lactobacillus plantarum adsorbed on distiller’s grains biochar (XIM) and encapsulated Lactobacillus plantarum on distiller’s grains biochar (BIM). The adsorption performance of these biochars was evaluated under varying conditions such as pHpH is a measure of how acidic or alkaline a substance is. A pH of 7 is neutral, while lower pH values indicate acidity and higher values indicate alkalinity. Biochars are normally alkaline and can influence soil pH, often increasing it, which can be beneficial More, dosage, initial Cd2+ concentration, and adsorption duration.

Adsorption Capacity and Efficiency

The maximum adsorption capacity and efficiency were observed at a pH of 6.0. At an equilibrium concentration of 60 mg/L of cadmium, XIM and BIM exhibited adsorption capacities of 8.40 mg/g and 12.23 mg/g, respectively. BIM consistently showed higher adsorption capacities than XIM across different cadmium concentrations.

Adsorption Mechanism

The adsorption mechanisms were investigated using various analytical techniques including isothermal adsorption modeling, kinetic modeling, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR).

For XIM, cadmium adsorption primarily involved physical adsorption and pore retention. The SEM and EDS analyses showed the presence of cadmium on the surface and within the pores of XIM, but no significant structural changes or new crystal formations were detected post-adsorption.

BIM, on the other hand, demonstrated a different mechanism. The adsorption process involved the formation of Cd(CN)2 crystals, as evidenced by XRD patterns and FTIR spectra. The SEM images showed significant morphological changes on the BIM surface, with pores covered by granular materials, indicating that BIM had a higher adsorption capacity for cadmium due to ion exchange and surface complexation reactions.

Factors Influencing Adsorption:

The adsorption performance varied with changes in biochar dosage, solution pH, and initial cadmium concentration. The adsorption capacity increased with the dosage up to a certain point, beyond which the efficiency plateaued. The optimal dosage was found to be 0.05 g for both XIM and BIM.

Adsorption efficiency improved with increasing solution pH, reaching a maximum at pH 6.0. At lower pH levels, high concentrations of H+ ions competed with Cd2+ for adsorption sites, reducing the overall adsorption efficiency.

The initial concentration of cadmium also influenced the adsorption process. Both XIM and BIM showed higher adsorption capacities with increasing cadmium concentrations, stabilizing at higher concentrations.

The study concludes that Lactobacillus plantarum immobilized on distiller’s grains biochar, especially when encapsulated, is highly effective in adsorbing cadmium from aqueous solutions. The encapsulated biochar (BIM) demonstrated superior adsorption capacity due to its unique mechanism involving the formation of Cd(CN)2 crystals. These findings suggest that using biochar derived from distiller’s grains as a carrier for immobilized microorganisms offers a viable and efficient method for treating cadmium-contaminated wastewater. This approach not only provides an effective solution for heavy metal remediation but also adds value to waste by-products from the liquor industry, promoting sustainable environmental practices.