Kochito, et al (2024) Manganese oxide-coffee husk and khat (Catha edulis) leftover 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 nanocomposites for removal of Cr (VI) from wastewater. Bull. Chem. Soc. Ethiop. https://dx.doi.org/10.4314/bcse.v38i5.3

This study focuses on the synthesis and application of manganese oxide-biochar nanocomposites made from coffee husk (CH) and khat leftovers (KL) to remove Cr(VI) from wastewater. The raw biochars were produced by pyrolyzing the biomassBiomass is a complex biological organic or non-organic solid product derived from living or recently living organism and available naturally. Various types of wastes such as animal manure, waste paper, sludge and many industrial wastes are also treated as biomass because like natural biomass these More at 300°C for one hour. Additionally, the biochar nanocomposites were created by treating the biomass with KMnO4 before pyrolysisPyrolysis is a thermochemical process that converts waste biomass into bio-char, bio-oil, and pyro-gas. It offers significant advantages in waste valorization, turning low-value materials into economically valuable resources. Its versatility allows for tailored products based on operational conditions, presenting itself as a cost-effective and efficient More, resulting in materials capable of removing up to 99.84% of Cr(VI) from water.

Industrial activities release heavy metals like chromium into the environment, posing significant health risks. Cr(VI) is particularly hazardous due to its high solubility and mobility, which allows it to infiltrate water sources and accumulate in living organisms. Traditional methods for removing Cr(VI), such as electrochemical techniques, ultrafiltration, ion exchange, and chemical precipitation, often involve high costs, energy consumption, and the generation of toxic sludge. In contrast, adsorption offers a more efficient and cost-effective solution.

Activated biochar, especially when combined with metallic oxide nanoparticles, has shown promise in improving adsorption capabilities for contaminants like Cr(VI). This study explored using manganese oxide-biochar nanocomposites, leveraging the abundant biomass waste of coffee husk and khat leftovers in Ethiopia. The synthesis involved immersing biomass in KMnO4, drying, and pyrolyzing the mixture, resulting in nanocomposites with enhanced porosityPorosity of biochar is a key factor in its effectiveness as a soil amendment and its ability to retain water and nutrients. Biochar’s porosity is influenced by feedstock type and pyrolysis temperature, and it plays a crucial role in microbial activity and overall soil health. Biochar More and surface area.

Characterization techniques, including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) analysis, confirmed the successful integration of manganese oxides into the biochar matrix. These analyses showed the amorphous structure and the presence of functional groups essential for Cr(VI) adsorption.

Batch adsorption studies revealed that the pristine biochars of CH and KL removed 74.98% and 84.78% of Cr(VI), respectively. However, the nanocomposites exhibited significantly higher removal efficiencies of 99.63% for MnOX-CHBNC and 99.84% for MnOX-KLBNC. The adsorption followed the Langmuir isotherm model, indicating monolayer adsorption on homogeneous surfaces, and adhered to pseudo-first-order kinetics.

The study also examined the effects of 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, adsorbent dose, contact time, and initial Cr(VI) concentration on adsorption efficiency. The optimum pH was found to be 2, as lower pH values enhance the positively charged surfaces of the adsorbents, facilitating the electrostatic attraction of Cr(VI) anions. The optimal adsorbent dose was determined to be 0.1 g for both nanocomposites, providing the highest removal efficiency without excessive aggregation that could reduce the effective surface area.

Moreover, the nanocomposites maintained high removal efficiencies over six adsorption-desorption cycles, demonstrating their potential for repeated use in practical applications. This reusability, combined with the low-cost production from abundant biomass waste, underscores the feasibility of these nanocomposites for large-scale wastewater treatment.

In conclusion, the manganese oxide-biochar nanocomposites derived from coffee husk and khat leftovers offer an effective, sustainable, and economical method for removing Cr(VI) from wastewater. These findings highlight the dual environmental benefits of managing agricultural waste and mitigating water pollution, paving the way for broader application in wastewater treatment technologies. Further studies involving real industrial effluents could provide additional insights into scaling up this promising technology.