ABSTRACT

In the present study, complex wastewater from the food industry was used to study the effect of ozonation and catalysed ozonation for chemical oxygen demand (COD) removal. The catalysts used were synthesized from agro-waste, activated carbon (AC) and plastic waste, multiwalled carbon nanotubes (MWCNTs)(MWCNT). The effect of various operating parameters, like ozone dosage, catalyst dosage, pH, on COD removal of food industry wastewater was investigated. The maximum COD removal was observed at ozone dose of 2gm/hr. MWCNTs(MWCNT) catalysed ozonation removes 85% COD and 48% total organic carbon (TOC) removal within 180 min at pH 9 and 74% COD and 36% TOC removal was observed for activated carbon catalysed ozonation for the same experimental conditions. A significant inhibition of COD removal was observed in the presence of tertiary-butyl alcohol. Using para-chlorobenzoic acid (p-CBA) as a probe compound, the hydroxyl radical exposure was determined for AC and MWCNT catalysed ozonation. The hydroxyl radical exposure was measured to understand the mechanism of catalytic ozonation and compare the performance of two different catalysts in terms of hydroxyl radical generation. It was found that hydroxyl radical exposure increases with increasing catalyst dose, which confirms the hydroxyl radical (OH.) pathway for COD reduction. The kinetic studies showed a 5.5time increment in rate for MWCNT catalysed ozonation and a 4 time increment for activated carbon catalysed ozonation when compared with standalone ozonation. The synergistic factor for MWCNTs and ozone was found to be 1.83 and for activated carbon and ozone, 1.5.

Highlights

• Catalysts used were synthesized from waste.

• Application of activated carbon and multiwalled carbon nanotubes for catalytic ozonation of real food wastewater was investigated.

• Effectiveness of standalone ozonation and catalytic ozonation was identified and compared.

• A multiwalled carbon nanotube presents higher catalytic performance than activated carbon for ozonation of real food wastewater.

• Hydroxyl radical mechanism of catalytic ozonation was confirmed by using p-CBA as a probe compound.

摘要

在本研究中，食品工业的复杂废水被用来研究臭氧化和催化臭氧化对化学需氧量 (COD) 去除的影响。使用的催化剂由农业废弃物、活性炭 (AC) 和塑料废弃物、多壁碳纳米管 (MWCNT) (MWCNT) 合成。考察了臭氧用量、催化剂用量、pH 值等各种操作参数对食品工业废水 COD 去除的影响。在 2gm/hr 的臭氧剂量下观察到最大 COD 去除率。多壁碳纳米管 (MWCNT) 催化臭氧化在 pH 9 下 180 分钟内去除 85% COD 和 48% 总有机碳 (TOC)，在相同实验条件下观察到活性炭催化臭氧化去除 74% COD 和 36% TOC。在叔丁醇存在下观察到 COD 去除的显着抑制。p -CBA) 作为探针化合物，确定了 AC 和 MWCNT 催化臭氧化的羟基自由基暴露。测量羟基自由基暴露以了解催化臭氧化的机理，并比较两种不同催化剂在羟基自由基生成方面的性能。结果发现，羟基自由基暴露随着催化剂剂量的增加而增加，这证实了用于 COD 还原的羟基自由基 (OH.) 途径。动力学研究表明，与独立臭氧化相比，MWCNT 催化臭氧化的速率增加了 5.5 倍，活性炭催化臭氧化的速率增加了 4 倍。发现 MWCNT 和臭氧的协同因子为 1.83，活性炭和臭氧的协同因子为 1.5。

强调

• 使用的催化剂是从废物中合成的。

• 研究了活性炭和多壁碳纳米管在实际食品废水催化臭氧化中的应用。

• 确定并比较了独立臭氧化和催化臭氧化的有效性。

• 多壁碳纳米管对实际食品废水的臭氧化具有比活性炭更高的催化性能。

• 以对CBA为探针化合物，证实了催化臭氧化的羟基自由基机理。