Biomass-based sustainable solutions for pulp & paper industry wastewater: a review of adsorption and advanced oxidation

This review critically examines the existing and emerging techniques for treating wastewater produced by Pulp and Paper Industry (PPI), highlighting their advantages, limitations, and environmental implications. PPI is one of the largest freshwater users and a major producer of industrial wastewater. Its effluents are contaminated, with high concentration of COD, suspended particles, organic matter, BOD, colorants, lignin derivatives, chlorinated compounds, and heavy metals. This review presents detailed examination of traditional treatment techniques such as sedimentation, coagulation-flocculation, activated sludge processes, and chemical oxidation that have been widely used. Response Surface Methodology (RSM) using Central Composite Design (CCD) was applied to optimize pH, adsorbent dose, contact time, and initial concentration for maximizing chlorophenol removal efficiency. The quadratic model developed was found statistically significant (F-value = 12.99) with excellent agreement between predicted and experimental results, confirming its robustness. The optimized conditions—around pH 6, 3 g/L adsorbent dose, and 40–45 min contact time—yielded the highest removal efficiency, validating the model’s predictive accuracy. Hybrid treatment systems, integrating multiple techniques, have gained attention due to their ability to enhance pollutant removal and reduce operational costs were also studied. The comparison of different treatment methods showed that combined systems such as electrocoagulation, adsorption, and advanced oxidation processes (AOPs) remove pollutants more effectively than single treatment methods and also help reduce operational problems. The review also explains the role of lignin-degrading enzymes, methods to reduce membrane fouling, and the need for low-energy hybrid treatment systems for better wastewater treatment. Future studies should focus on large-scale industrial applications, reducing energy use, improving membrane fouling, adsorbents regeneration, and evaluating the overall environmental and economic benefits of these treatment methods. Overall, this review provides a significant resource for industry professionals and researchers seeking more sustainable and innovative solutions in this field.