Floating sandwich-type electro-Fenton: A feasible process to remove micro-pollutants through adsorption enrichment and enhanced oxidation efficiency

Pre-treatment of composite industrial wastewater by Fenton and electro-Fenton oxidation processes

The present study aims to characterize three industrial wastewater samples collected from petrochemical, food and beet sugar industries to determine the pollution potential and select the appropriate pre-treatment approach. According to the biodegradability profile of the multi-sourced mixed (composite) sample, the advanced oxidation process (AOPs) namely, Fenton (F) and Electro-Fenton (EF) were adopted as pre-treatment techniques and the operating parameters such as time, type of electrodes, pH, voltage, iron and H2O2 concentrations were critically examined. Analysis of Variance (ANOVA) was conducted to compare the performance efficiency of F& EF AOPs for treating the composite samples and the total operating costs for both approaches were assessed. The results revealed that, the initial values of the composite sample were 7.11, 19.2, 32.6, 19.3, 937, 1512, 860, 3.9, 2110 and 2.34 for pH, Total Dissolved Solids (TDS), Electrical Conductivity (EC), Salinity, BOD, COD, Oil and grease (O&G), Total Phosphorous (TP), Total Suspended Solids (TSS) and Total Kjeldahl Nitrogen (TKN), respectively. In addition, EF process achieved more removal efficiency for COD, O&G, BOD, TSS, and TKN (84.3%, 69%, 85%, 72% and 71.27%) compared to Fenton which displayed 78.43%, 66%, 69%, 70.1%, and 61%, respectively. Moreover, there are statistically significant differences (p < 0.05) between the initial and final (pretreated) values of the composite industrial wastewater for the addressed parameters and EF was significantly (p < 0.05) more effective than F process. The total operating costs were 3.117 and 2.063$ for F and EF, respectively, which confirmed that EF is more efficient and cost effective than F process. It was concluded that electro-Fenton process is favorable, eco-friendly and cost-effective option for pretreating real complicated multi-sourced industrial wastewater. The present study demonstrated a new avenue for achieving efficient management of industrial wastewater generated from similar industries.

Improvement of Fe(Ⅲ)/percarbonate system by molybdenum powder and tripolyphosphate: Co-catalytic performance, low oxidant consumption, pH-dependent mechanism

The homogeneous sodium percarbonate (SPC) systems are limited by narrow pH range, ineffective consumption of oxidant, and weak reusability of catalyst. Herein, molybdenum (Mo) powder and sodium tripolyphosphate (STPP) were selected to overcome these challenges. Sulfamethoxazole (SMX), as a model contaminant, was almost completely degraded in 60 min with higher removal rate (0.1367 min-1) than the Mo or STPP-absent system. In addition, Mo/STPP-Fe(Ⅲ)/SPC system was cost-effective in terms of oxidant consumption, requiring only 0.2 mM SPC. About activation mechanism, the main active species for SMX degradation was pH-dependent, with hydroxyl radical (·OH) as the dominant active species at pHi = 7 and ·OH, carbonate radical (CO3·-), and superoxide radical (O2·-) derived from a series of chain reaction at pHi = 10, respectively. Due to the generation of various electrophilic free radical, the system exhibited excellent performance towards electron-rich pollutants under a wide pH range. Furthermore, Mo exhibited excellent stability and reusability. SMX was degraded through hydroxylation, N-S cleavage, amino and sulfanilamide oxidation into intermediates whose toxicities were evaluated by Toxicity Estimation Software Tool (T.E.S.T.) software. This work provided new insights to Fe/SPC system towards high-efficiency and low consumption treatment of practical application.