The treatment of industrial wastewater from dye and textile operations poses a critical environmental challenge globally due to the complex chemical structures and low biodegradability of azo dyes. In a recent paper published in Scientific Reports, authors Vishal Kumar U. Shah, Pratima Gajbhiye, Anand Mohan Yadav, Jay B. Trivedi, Aparna Singh, Aditee Pandya, Xu Yong, Choon Kit Chan, Saurav Dixit, Anand Patel, and Md Irfanul Haque Siddiqui investigated a physical and chemical purification method. The team collected authentic, heavily contaminated wastewater directly from an operating dyeing and printing facility in Kadodra, Surat, Gujarat, India, ensuring that the trial reflected realistic industrial complexities rather than simplified synthetic laboratory solutions. Their research successfully pioneered a sequential treatment combining tailored agricultural waste charcoalCharcoal is a black, brittle, and porous material produced by heating wood or other organic substances in a low-oxygen environment. It is primarily used as a fuel source for cooking and heating.   More with targeted ozone gas oxidation to concurrently lower chemical oxygen demand and eliminate dense coloration.

The primary discovery centers on the exceptional efficiency of agricultural waste derived from Canna indica leaves when modified by specific alkaline activating agents. When the plant material is pyrolyzed and treated with potassium hydroxide, it develops a highly sophisticated, interconnected mesoporous network with a significantly increased total surface area. This physical expansion allows the modified charcoal to act as an intense sponge, yielding a maximum theoretical adsorption capacity of 357.14 milligrams of pollutant per gram of material. In direct comparison, raw biochar modified with sodium hydroxide achieved a lower maximum theoretical capacity of 333.33 milligrams per gram. The superior execution of the potassium-treated variant stems from its enhanced ability to preserve internal pathway volumes and fracture complex polymer matrices during processing, providing a high density of active capture points.

The scientific analysis confirmed that the primary control mechanism regulating pollutant removal is chemisorption, meaning that strong chemical bonds are forged between the functional groups on the charcoal surface and the passing dye molecules. Structural evaluation highlighted that the abundance of hydroxyl, carboxyl, and aromatic carbon groups on the biochar allows for intense hydrogen bonding and electrostatic attraction. This chemical bonding works in perfect harmony with the physical pore filling of the mesoporous material. By testing the process against variable concentrations of real textile effluent, the researchers demonstrated that a high correlation exists with pseudo-second-order kinetic paths, proving that chemical interactions limit the overall speed of the initial absorption phase.

The inclusion of an integrated ozonation stage immediately following the biochar filtration yields a profound synergistic reaction that overcomes the limitations of standalone carbon filtration. Injecting ozone gas into the pre-treated solution at an optimized rate triggers direct and indirect advanced oxidation processes. The ozone gas directly attacks electron-rich double bonds within the complex ring structures of the hazardous azo dyes, effectively shattering the chromophore molecules responsible for the wastewater color. Concurrently, in the neutral to slightly alkaline environment, the ozone rapidly decomposes into highly reactive hydroxyl radicals that non-selectively oxidize persistent organic materials into harmless base components. This dual action enables the system to clean highly concentrated waste fluid that possesses an initial chemical oxygen demand of 2850 milligrams per liter and a color density of 1450 platinum-cobalt units.

Statistical evaluation using Response Surface Methodology under a Box-Behnken Design established the exact hierarchy of importance for the operational variables. The team discovered that solution acidity is the single most critical factor determining overall success, followed sequentially by the absolute adsorbent dose, total contact duration, and the precise ozonation gas flow rate. The statistical model successfully predicted optimal purification when utilizing 2.5 grams per liter of potassium-modified charcoal at a slightly alkaline 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 of 8.21, paired with a contact time of 17 hours and an ozone injection rate of 79.48 milliliters per minute. Under these exact parameters, the system achieved a validated 95.66% decrease in chemical oxygen demand and 98.23% removal of all visible color, offering a highly practical, reliable, and economically viable roadmap for large-scale industrial water purification.

Source: Shah, V. K. U., Gajbhiye, P., Yadav, A. M., Trivedi, J. B., Singh, A., Pandya, A., Yong, X., Chan, C. K., Dixit, S., Patel, A., & Siddiqui, M. I. H. (2026). Integrated adsorption-ozonation process using activated canna indica biochar for enhanced COD and color removal from real textile effluent. Scientific Reports.