Department of Chemical Engineering, Indian Institute of Technology Roorkee, Roorkee, 247667, India.
Department of Chemical Engineering, Indian Institute of Technology Guwahati, Guwahati, Assam, 781039, India.
Environ Sci Pollut Res Int. 2017 Jan;24(2):1953-1966. doi: 10.1007/s11356-016-7986-1. Epub 2016 Oct 31.
Purified terephthalic acid (PTA) plant of a petrochemical unit generates wastewater having high pollution load. Acid treatment of this wastewater reduces the chemical oxygen demand (COD) load by more than 50%, still leaving substantial COD load (>1500 mg/L) which should be removed. The present study reports on the use of a bio-waste-adsorbent bagasse fly ash (BFA) for the reduction of COD and other recalcitrant acids from this wastewater. The BFA showed basic character and was mesoporous with a BET specific surface area of 82.4 m/g. Optimum conditions for the adsorptive treatment of acid-pretreated PTA wastewater were found to be as follows: initial pH (pH) = 4, BFA dosage = 15 g/L, and contact time = 3 h. Adsorption treatment resulted in 58.2% removal of COD, 96.3% removal of terephthalic acid (TA), and 99.9% removal of benzoic acid (BA). TA and BA were removed from the pretreated PTA wastewater through precipitation and sedimentation of un-dissociated acid molecules inside the mesopores of the BFA. The results showed that the COD removed by the BFA followed pseudo-second-order kinetics. Equilibrium sorption data were best correlated by the Freundlich isotherm. The process of adsorptive removal of COD was found to be exothermic. The change in the Gibbs free energy was found to be negative, suggesting that the adsorption process is spontaneous and feasible for the treatment of PTA wastewater.
石化装置精对苯二甲酸（PTA）厂产生的废水具有高污染负荷。该废水的酸处理可将化学需氧量（COD）负荷降低 50%以上，但仍留有大量 COD 负荷（>1500mg/L）需要去除。本研究报告了使用生物废物吸附剂甘蔗渣粉煤灰（BFA）来降低该废水中 COD 和其他难降解酸的情况。BFA 呈碱性，具有中孔结构，BET 比表面积为 82.4m/g。吸附预处理 PTA 废水的最佳条件如下：初始 pH（pH）=4，BFA 用量=15g/L，接触时间=3h。吸附处理可使 COD 去除率达到 58.2%，对苯二甲酸（TA）的去除率达到 96.3%，苯甲酸（BA）的去除率达到 99.9%。TA 和 BA 通过 BFA 中孔内未离解酸分子的沉淀和沉降从预处理 PTA 废水中去除。结果表明，BFA 去除的 COD 遵循伪二级动力学。平衡吸附数据与 Freundlich 等温线拟合最佳。吸附去除 COD 的过程是放热的。吉布斯自由能的变化为负值，表明吸附过程是自发的，可用于处理 PTA 废水。
