ABSTRACT

A two-step process involving coagulation-flocculation followed by solar photocatalysis – based Advanced Oxidation Process (AOP) using TiO₂-Reduced Graphene Oxide (TRGO) nanocomposite as catalyst has been employed for the treatment of pulp and paper mill effluent. As the effluent is loaded with a high amount of organics with initial chemical oxygen demand (COD) as high as 3516, a pre-treatment is required before applying photocatalytic treatment. Coagulation-flocculation was identified as an effective pre-treatment strategy. Among the various coagulants tested, CuSO₄.5H₂O showed the best % COD reduction of 84 at pH 6, at a loading of 5 g/L. The primary treatment of coagulation improved the biodegradability index from 0.23 to 0.37. TRGO photocatalyst, employed in the second stage of photocatalytic treatment was synthesised by an ultrasound assisted solvothermal method and well characterised by various spectroscopic/analytical tools. The composite was found to be an efficient solar photocatalyst and achieved 1.76 and 2.1 times more COD reduction than synthesised TiO₂ and commercial P25 respectively. The final effluent after the combined treatment was neutral and the biochemical oxygen demand (BOD) and COD were 11.7 and 120 mg/L respectively which were below the given limit of National Environmental Quality Standards.

摘要

_{使用 TiO 2}还原氧化石墨烯 (TRGO) 纳米复合材料作为催化剂的两步工艺包括凝聚-絮凝和太阳能光催化 - 基于高级氧化工艺 (AOP)已用于处理纸浆和造纸厂废水。由于流出物中含有大量有机物，初始化学需氧量 (COD) 高达 3516，因此在进行光催化处理之前需要进行预处理。混凝-絮凝被确定为一种有效的预处理策略。在测试的各种混凝剂中，CuSO ₄ .5H ₂O 在 5 g/L 的负载下，在 pH 6 下显示出最佳的 % COD 减少 84。混凝的初级处理将生物降解性指数从0.23提高到0.37。用于光催化处理第二阶段的 TRGO 光催化剂是通过超声辅助溶剂热法合成的，并通过各种光谱/分析工具进行了很好的表征。_{该复合材料被发现是一种高效的太阳能光催化剂，其 COD 减少量分别比合成的 TiO 2}和商业 P25高 1.76 倍和 2.1 倍。联合处理后的最终出水为中性，生化需氧量（BOD）和COD分别为11.7和120 mg/L，低于国家环境质量标准规定的限值。