Catalytic reduction of in-flow aqueous Cr(VI) using a slurry of activated carbon fiber-supported Ni nanoparticles in a coiled flow inverter,Reaction Chemistry & Engineering

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Catalytic reduction of in-flow aqueous Cr(VI) using a slurry of activated carbon fiber-supported Ni nanoparticles in a coiled flow inverter
Reaction Chemistry & Engineering ( IF 3.4 ) Pub Date : 2022-08-09 , DOI: 10.1039/d2re00226d
Rakshit Kajala ₁ , Shivam Singh Tomar ₁ , Nishith Verma _{1,

2} , K. D. P. Nigam ₃

Affiliation

This study presents a coiled flow inverter (CFI) for the first time as an alternative technology to the conventional packed bed reactors for carrying out the in-flow aqueous phase catalytic reduction of hexavalent chromium (Cr(VI)). Cr(VI) is reduced to its less-toxic trivalent state, namely, Cr(III), utilizing an environmentally benign reducing agent – formic acid. An aqueous slurry of micron-sized activated carbon fiber (ACF)-supported Ni metal nanoparticles is used for the first time to successfully catalyse the reduction reaction in the serially connected CFI units. The data show the Cr(VI) to Cr(III) conversion of ∼98% for the 4 mM-Cr(VI) solution under the optimized conditions, 200 cc min⁻¹ feed flow rate, 5 mg mL⁻¹ Ni/ACF catalyst dose, and 0.8 M concentration of formic acid, in four CFI units connected in series. A pseudo first-order kinetic rate constant of 1.94 min⁻¹ measured for the reduction reaction is found to be in the same order of magnitude as that reported in the literature for the batch mode. The data also confirm the competitive efficiency of the proposed CFI-mediated heterogeneous reaction compared to that of the presently used packed bed reactors for the catalytic reduction of aqueous Cr(VI), attributable to the intensified mixing characteristics of the CFI.

中文翻译：

在盘绕流逆变器中使用活性炭纤维负载的 Ni 纳米颗粒浆液催化还原流入的水性 Cr(VI)

本研究首次提出了一种盘管流动逆变器（CFI）作为传统填充床反应器的替代技术，用于进行六价铬（Cr（VI））的流入水相催化还原。利用对环境无害的还原剂——甲酸，将Cr( VI ) 还原成毒性较小的三价状态，即 Cr( III )。首次使用微米级活性碳纤维 (ACF) 负载的 Ni 金属纳米粒子的水浆成功催化串联 CFI 单元中的还原反应。数据显示，对于 4 mM-Cr(VI)，Cr( VI )到 Cr( III ) 的转化率约为 98%) 溶液在优化条件下，200 cc min ^-1进料流速，5 mg mL ^-1 Ni/ACF 催化剂剂量和 0.8 M 浓度的甲酸，在四个串联的 CFI 单元中。发现为还原反应测得的1.94 min ^-1的伪一级动力学速率常数与文献中报道的间歇模式的数量级相同。数据还证实了所提出的 CFI 介导的非均相反应与目前使用的用于催化还原水性 Cr( VI ) 的填充床反应器相比具有竞争效率，这归因于 CFI 的强化混合特性。

更新日期：2022-08-09

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