A bio-nanocluster (Fe₃O₄@bacteria) was prepared by simply mixture using the bacterial suspension and Fe₃O₄ nanoclusters to remove Congo red (CR) contamination from water resources. The bio-nanocluster was characterized by SEM, TEM and XPS. Adsorption efficiency, adsorption process and adsorption mechanism were comprehensively investigated. The maximum adsorption capacity (Q_m) of CR dye onto the Fe₃O₄@bacteria peaked at 320.1 mg/g, which was 2.88 times that of Fe₃O₄ under the same condition. Based on the equilibrium and kinetic studies, the Langmuir isotherm theory and pseudo-first-order model is appropriate to describe the adsorption process. The adsorption of CR is spontaneous and exothermic according to the thermodynamics parameters (ΔG^θ, ΔH^θ and ΔS^θ). The adsorption force dominated the Van der Waals force, biofloculation and chemisorption. The Fe₃O₄@bacteria could be applied potentially as an absorbent with high efficiency and environmentally friendly remediation of dyeing wastewater.

Aims The adsorption behavior and mechanisms of the surface modified activated carbon with bacteria was evaluated. Methods 16S rRNA was employed to indentify the hydrocarbon‐degrading bacteria. The bacteria was characterized by TEM and electron microscope. The surface modified activated carbon with bacteria was characterized by SEM. The adsorption behavior was tested by static adsorption and dynamic adsorption. Conclusion The adsorption efficiency of the modified activated carbon was high when pH was weak acidic, and the adsorption capacity increased with the increase of temperature ranging from 20°C‐35°C. The adsorption capacity peaked at 234.6 mg/g at 25°C, which was six fold higher than that of activated carbon. The pseudo‐first‐order kinetic can more accurately assess Congo Red adsorption on the two adsorbents. The adsorption of Congo Red by bacteria surface modified activated carbon fitted well with the Langmuir's model. The adsorption process was endothermic, and the biological floccules were formed during the adsorption. The physical adsorption is the main driving force. Significance and impact of the study The results indicate that the bacteria surface‐modified activated carbon can be used effectively as an adsorbent to eliminate Congo Red from aqueous solutions.

The remove of oxytetracycline hydrochloride (OTC) antibiotics from water presents both significant challenges and importance. In this study, magnetic activated carbon (MAC) was synthesized from powdered activated carbon and ferric compounds using an alkaline co-precipitation process. Various characterizations techniques employed to assess the microscopic morphology, pore structure, and surface functionality of the adsorbents. The maximum equilibrium adsorption (q_m) of MAC for OTC at temperature of 20, 25, 30, 35, and 40°C were found to be 93, 112, 118, 108, and 117 mg/g, respectively, as determined by the Langmuir isotherm adsorption model. Thermodynamic and adsorption site energy analyses indicated that the adsorption process is a spontaneous endothermic reaction at elevated temperatures. During the OTC removal process, both chemisorption and physisorption mechanisms were observed, with adsorption site energies ranging from 4 to 16 kJ/mol, suggesting that chemical adsorption likely played a predominant role. The adsorbent material demonstrated excellent adsorption efficiency and a spontaneous nature, making it a promising candidate for the environmentally friendly treatment of antibiotic-contaminated wastewater.