The escalating global water crisis, fueled by an influx of non-biodegradable contaminants, presents a formidable challenge to environmental scientists and policymakers alike. From industrial dyes to pharmaceutical residues, these pollutants infiltrate water systems, posing severe ecological and health risks. Rose Bengal (RB) dye, a fluorescein derivative, is notorious for its toxicity, impacting mucous membranes and breathing upon inhalation. Similarly, pharmaceuticals like Ofloxacin (Oflox), an antibiotic, are frequently detected in various water bodies due to improper disposal and human excretion, potentially fostering antibiotic-resistant bacteria. Addressing this pervasive issue, researchers are increasingly turning to advanced oxidation processes (AOPs), particularly photocatalysis, for their environmentally friendly, cost-effective, and highly efficient capabilities in breaking down organic pollutants into benign compounds. A recent study by Khushboo Kumari, N. S. Moyon, and Mohammed Ahmaruzzaman, featured in Scientific Reports, introduces a novel and sustainable approach to water decontamination. They developed a ternary nanocomposite consisting of tin oxide (SnO2), fly ashAsh is the non-combustible inorganic residue that remains after organic matter, like wood or biomass, is completely burned. It consists mainly of minerals and is different from biochar, which is produced through incomplete combustion.   Ash Ash is the residue that remains after the complete More (FA), and 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 (BC), harnessing waste and natural resources as a robust platform for photocatalytic degradation. This innovative composite not only tackles critical water pollution but also provides an appealing method for waste management and cost reduction.

The research meticulously engineered the nanocomposite using a sol-gel method, with the biochar specifically prepared from dried water hyacinth leaves collected from NIT Silchar, Assam. Comprehensive characterization techniques were employed to scrutinize the composite’s structural, morphological, compositional, and surface area properties. These included Transmission Electron Microscopy (TEM), X-ray Powder Diffraction (XRD), Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS), Photoluminescence (PL) spectroscopy, and UV-Vis Diffuse Reflectance Spectroscopy (DRS).

Biochar nanocomposite demonstrated extraordinary photocatalytic effectiveness under natural sunlight. It achieved an impressive 99.12% degradation of Rose Bengal dye and 88.08% degradation of Ofloxacin pharmaceutical. Remarkably, these high degradation rates were accomplished within a mere 60 minutes for each pollutant, utilizing a minimal catalyst dose of 0.01 g/L.

The study extensively investigated how various environmental factors influenced the photodegradation efficiency. 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 emerged as a critical determinant. For RB dye, the highest degradation efficiency of 99.12% was observed at pH 3. This is primarily because at lower pH levels, the photocatalyst’s surface acquires a positive charge, enhancing its electrostatic attraction with the negatively charged RB dye molecules. Ofloxacin, on the other hand, exhibited its peak degradation efficiency of 88.08% at pH 7, with performance declining beyond this point.

Regarding catalyst dosage, the research indicated a direct correlation between increasing the amount of Biochar nanocomposite and improved photodegradation efficiency. The optimal catalyst dose for both RB and Ofloxacin was determined to be 0.01 g/L. This specific dosage maximized the number of active sites available on the photocatalyst’s surface and enhanced photon absorption, leading to greater production of active radicals essential for degradation. However, exceeding this optimal dosage did not yield further improvements in degradation efficiency; instead, it led to a decline. This saturation effect is attributed to the aggregation of unbound catalyst particles, which increases the solution’s opacity and obstructs the path of photons, thereby hindering the degradation process.

The exceptional photocatalytic activity observed in the Biochar nanocomposite can be attributed to several key material properties. The composite possesses a diminished bandgap which enables the material to absorb a broader spectrum of visible light, significantly boosting its photocatalytic capabilities. Furthermore, photoluminescence (PL) spectroscopy revealed that the Biochar nanocomposite effectively reduced the recombination rate of photogenerated electron-hole pairs compared to its individual components. This efficient charge separation at the composite’s interface is crucial for its superior performance. The incorporation of functional groups on the surface of biochar also plays a vital role by significantly improving the dispersion of photocatalysts within the composite, contributing to the overall enhanced activity.

its impressive degradation capabilities, the Biochar nanocomposite exhibited remarkable reusability, a critical factor for practical applications. The photocatalyst maintained a degradation efficiency of over 75% for up to five consecutive cycles. This sustained operational capacity underscores the composite’s potential as a promising and cost-effective solution for long-term water treatment applications. The exceptional stability observed in the material is primarily attributed to the efficient charge segregation facilitated by the composite structure and the inherent reinforcement provided by the biochar matrix.

This study marks a significant advancement in environmentally sustainable water decontamination. The development of the Biochar nanocomposite provides a highly effective and reusable solution for addressing the pervasive issue of organic pollutants in water. Its ability to degrade both dyes and pharmaceuticals under visible light, coupled with its robust stability, positions it as a promising technology for future environmental remediation efforts.

Source: Kumari, K., Moyon, N. S., & Ahmaruzzaman, M. (2025). Environmentally sustainable fabrication of SnO2/fly ash/biochar nanocomposite for enhanced photocatalytic performance for degradation of Ofloxacin and Rose Bengal.