Bacillus subtilis-CuO nanocomposites as a sustainable solution for Congo red dye remediation: Adsorption studies and kinetic modeling
Turki Alamri, Jawahir A. Mokhtar, Elhagag Ahmed Hassan, Steve Harakeh, Hatoon A. Niyazi, Hanouf A. Niyazi, Turki S. Abujamel, Hend Alrasheedi, Noura A. Chehab, Mohamed Abd El–Aal
Abstract
Aquatic ecosystem contamination with Congo red (CR), leads to significant environmental issues due to its persistence and toxicity. This study aims to develop a sustainable and effective strategy for CR removal through combined CuO nanoparticle (NP) adsorption and Bacillus subtilis dried biomass (DBS) biosorption. Congo red removal was evaluated by using DBS, pure CuO nanoparticles, and CuO/DBS nanocomposites containing 10 % and 50 % of CuO. The adsorption of CR dye was examined under varying parameters, including contact time, pH, initial dye concentration, and temperature. The XRD and FTIR analyses confirmed the successful incorporation of CuO NPs onto the surface of DBS. The TEM image of the nanocomposite with 50 % CuO showed semi-spherical particles with an average diameter of 76.3 nm and some large agglomerated particles. The results demonstrated that the adsorbents exhibited effective adsorption performance for CR dye under optimal conditions (30 min contact time, pH 7, and an initial CR concentration of 10 ppm). The adsorption kinetics of the tested samples followed a pseudo-second-order model, while the Langmuir isotherm provided the best fit for CR removal. According to the Langmuir model, the maximum adsorption capacity (q m ) reached 255.1 mg/g for the 50 % CuO/DBS nanocomposite. The bio-nanocomposite system exhibited better CR removal efficiency compared to individual components, supporting the synergistic effect through the combination of biological and nanotechnological principles. The results offer a dual strategy for wastewater treatment, providing an efficient, eco-friendly process for eliminating toxic dyes while ensuring cost-effectiveness and environmental compatibility.