Aluminum chloride induced ferrate activation for p-arsanilic acid removal: The significant synergism mechanism and enhanced role of reactive Fe(IV)/Fe(V)

• Published in: Separation and purification technology 2024-09, Vol.343, p.127121, Article 127121
• Main Authors: Kong, Yanli, Lu, Fan, Huang, Zhiyan, Nie, Yong, Chen, Zhonglin, Ma, Jiangya
• Format: Article
• Language: English
• Subjects: Coagulation; Iron species; Oxidation; P-arsanilic acid; Potassium ferrate
• ISSN: 1383-5866; 1873-3794
• DOI: 10.1016/j.seppur.2024.127121

[Display omitted] •A novel highly centralized oxidation and coagulation (HOC) system of K2FeO4/AlCl3 was constructed.•K2FeO4 and AlCl3 in HOC system had a significant synergism mechanism.•AlCl3 induced K2FeO4 self-decomposition into more Fe(V)/Fe(IV) and enhanced the Fenton reaction.•AlCl3 increased the contribution of Fe(V)/Fe(IV) of K2FeO4 for ASA removal.•K2FeO4 also affected the transformation and distribution of aluminum hydrolyzed species. The practical applications of potassium ferrate (K2FeO4) are limited due to self-decomposition at nearly neutral pH and low removal efficiency for electron deficient pollutants. That is, K2FeO4 was often insufficient to produce sufficient oxidative material, so the lack of oxidative reactivity remained a pressing problem. This study proposed an effective induction of K2FeO4 activation by aluminum chloride (AlCl3) in a novel highly concentrated simultaneous oxidation and coagulation (HOC) system of K2FeO4/AlCl3. It innovatively focused on the interaction between K2FeO4 and AlCl3 for the removal of p-arsanilic acid (ASA) in a HOC system. The HOC system exhibited higher ASA removal (62.6%) in a shorter period of time compared to K2FeO4 oxidation (28.0%) and pre-oxidation-coagulation (POC) system (51.6%) with the addition of 1.5 mgAl/L of AlCl3 at pH 7. AlCl3 could induce the self-decomposition of K2FeO4, and more importantly, it could facilitated the conversion of Fe(VI) into the more reactive Fe(V)/Fe(IV) species for ASA removal. Moreover, AlCl3 hydrolysis promoted the in-situ H2O2 generation from K2FeO4 decomposition, enhancing Fenton-like reaction and increasing OH and O2– for ASA removal. K2FeO4 greatly influenced AlCl3 hydrolysis and promoted rapid transformation of small polyaluminum Ala and medium polyaluminum Alb to colloidal high polyaluminum Alc. The content of Fe elements in the flocs produced by the HOC-ASA floc system was 19.27%, which was much higher than the 4.58% of the POC-ASA system, which enhanced the interfacial reaction and electron transfer and facilitated the removal of ASA.