Exploring the viability of peracetic acid-mediated antibiotic degradation in wastewater through activation with electrogenerated HClO.

Electrochemical advanced oxidation processes (EAOPs) face challenging conditions in chloride media, owing to the co-generation of undesirable Cl-disinfection byproducts (Cl-DBPs). Herein, the synergistic activation between in-situ electrogenerated HClO and peracetic acid (PAA)-based reactive species in actual wastewater is discussed. A metal-free graphene-modified graphite felt (graphene/GF) cathode is used for the first time to achieve the electrochemically-mediated activation of PAA. The PAA/Cl- system allowed a near-complete sulfamethoxazole (SMX) degradation (kobs =0.49 min-1) in only 5 min in a model solution, inducing 32.7- and 8.2-fold rise in kobs as compared to single PAA and Cl- systems, respectively. Such enhancement is attributed to the occurrence of 1O2 (25.5 µmol L-1 after 5 min of electrolysis) from the thermodynamically favored reaction between HClO and PAA-based reactive species. The antibiotic degradation in a complex water matrix was further considered. The SMX removal is slightly susceptible to the coexisting natural organic matter, with both the acute cytotoxicity (ACT) and the yield of 12 DBPs decreasing by 29.4 % and 37.3 %, respectively. According to calculations, HClO accumulation and organic Cl-addition reactions are thermodynamically unfavored. This study provides a scenario-oriented paradigm for PAA-based electrochemical treatment technology, being particularly appealing for treating wastewater rich in Cl- ion, which may derive in toxic Cl-DBPs.

Iron(III) extraction from chloride media by N,N'-tetrasubstituted malonamides: an interfacial study.

The interfacial behaviour of two N,N'-tetrasubstituted malonamides, N,N'-dimethyl-N,N'-diphenyl malonamide (DMDPHMA) and N,N'-dimethyl-N,N'-dicyclohexylmalonamide (DMDCHMA), in the liquid-liquid (L/L) extraction of iron(III) from hydrochloric acid solutions, was studied. The experimental results obtained validate the absence of third phases for these systems. The equilibrium adsorption constants and surface excess concentrations, estimated by the Szyszkowski model, explain the experimental extraction efficiency patterns for both malonamides in the two diluents tested, 1,2-dichloroethane (1,2-DCE) and toluene. A solvation type mechanism is in accordance with all the results obtained, accounting for the structural and diluent effects observed.