Aluminosilicate-catalyzed electroreduction of nitrate anion—An approach through alkalinity analysis

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• 作者：Ahmed Enmili^a ; ^{aenmili@gmail.com} ; Abdelkrim Azzouz^c ; ^{azzouz.a@uqam.ca} ; ^{abdelkrimazzouz@yahoo.com} ; Vasilica-Alisa Arus^b ; Fré ; dé ; ric Monette^a
• 关键词：Water treatment ; Nitrate electroreduction ; Clay minerals ; Catalysis ; Alkalinity
• 刊名：Electrochimica Acta
• 出版年：2016
• 出版时间：20 December 2016
• 年：2016
• 卷：222
• 期：Complete
• 页码：1064-1071
• 全文大小：1473 K
• 卷排序：222

文摘

Aluminosilicate catalysts (bentonite, illite-montmorillonite mixture ([I + M]), kaolinite and clinoptilolite) showed catalytic activity in the electroreduction of nitrates using stainless steel electrodes in the presence of salts. Addition of NaCl and KCl resulted in process enhancement, affording nitrate removal yields of up to 95% after 30–60 min. They were found to improve of the ionic strength of the aqueous media, without undergoing precipitation with increasing alkalinity in time. Their neutral intrinsic pH seems to preserve the composition of the stainless steel electrodes, and to prevent salt electrolysis into metals as with magnesium. The process selectivity towards nitrogen was examined through a judicious approach involving deeper insights in alkalinity evolution. The lower alkalinity in the presence of catalyst was partly explained in terms of ammonia consumption via ion-exchange. A part of alkalinity was found to arise from the continuous formation of ammonia, favored by chemical equilibrium shift for compensating the adsorbed amount of NH4+ cations until saturation. These results demonstrate unequivocally that low cation exchange capacity and/or previous saturation of the catalyst by NH4+ cations are essential requirements for hindering the formation of ammonia. This opens new prospects for silica-rich materials for effective nitrate removal without residual ammonia in waters.