Paper and pulp industry is one of the notorious polluters of the environment. It has been categorized as one of the most polluting industries due to discharge of huge volumes of highly colored and toxic waste water in the environment causing pollution of land air and water. According to industry experts, approximately 85% of the water used in the paper and pulp industry is used as process water, resulting in relatively large quantities of contaminated water and necessitating the use of onsite wastewater treatment solutions. Treatment options include primary treatment such as clarification to remove solids and particulate matter, and secondary biological treatment processes for removing biodegradable organic matter and decreasing the effluent toxicity.One of the components of effluent is lignin which is mostly burned to generate the power. However, because lignin-rich wastes are wet and lignin has a lower energy content than coal, its value in this role is limited to well under $50/dry ton. Therefore conversion of lignin to higher value fuels and chemicals will significantly enhance overall biorefinery competitiveness and reduces the dependence on fossil fuels.There are several techniques which are common for lignin valorization viz. pyrolysis, combustion and photocatalysis. Sonophotocatalytic degradation of organic molecules is the most effective and economic process for solving the toxic environmental impact of hazardous wastes and toxic pollutants in aqueous medium.
Sonophotocatalysis offers a superior solution to many other conventional treatment solutions employed in paper and pulp industry. The main advantages of this method are that (i) it offers a good replacement for the energy-intensive conventional treatment methods with the capacity for using renewable and pollution-free solar energy, (ii) leads to the formation of harmless products, (iii)mild reaction conditions and finally,the reaction time is modest and a lesser chemical input is required.The effective cost for setting up of this recycling plant can be recovered easily from valuable chemicals generated as the end product, Also, its dependence on solar energy makes it a green technology and reduces the overall contribution to global warming.