Heng Lin

The Application of Electro-Fenton Process for the Treatment of Artificial Sweeteners

This chapter presents the degradation and mineralization of emerging trace contaminants artificial sweeteners (ASs) in aqueous solution by electro-Fenton process in which hydroxyl radicals were formed concomitantly by •OH formed from electrocatalytically generated Fenton’s reagent in the bulk solution and M(•OH) from water oxidation at the anode surface. Experiments were performed in an undivided cylindrical glass cell with a carbon-felt cathode and a Pt or boron-doped diamond (BDD) anode. The effect of catalyst (Fe2+) concentration and applied current on the degradation and mineralization kinetics of ASs was evaluated. The absolute rate constants for the reaction between ASs and •OH were determined. The formation and evolution of short-chain carboxylic acids as well as released inorganic ions, and toxicity assessment during the electro-Fenton process have been reported and compared.

Degradation of bisphenol A by electro-enhanced heterogeneous activation of peroxydisulfate using Mn-Zn ferrite from spent alkaline Zn-Mn batteries

Mn-Zn ferrite (Mn0.6Zn0.4Fe2O4) was prepared by a gel method using spent alkaline Zn-Mn batteries as raw materials and employed as catalyst to degrade bisphenol A (BPA) by electro-enhanced heterogeneous activation of peroxydisulfate (PDS). The effects of initial pH, current density, PDS concentration, and Mn-Zn ferrite dosage on BPA removal were investigated. The formation of reactive radicals was verified by electron paramagnetic resonance (EPR) spectroscopy. The results of radical quenching experiments indicate that surface-bound sulfate and hydroxyl radicals played an important role in BPA removal. The stability of Mn0.6Zn0.4Fe2O4 catalyst was investigated by cycling experiments, which indicates Mn0.6Zn0.4Fe2O4 is stable and can be reused. This work also provides an alternative way for the reutilization of spent alkaline Zn-Mn batteries.

Selective adsorption of phenanthrene dissolved in Tween 80 solution using activated carbon derived from walnut shells

In order to remove phenanthrene (PHE) from surfactant solution, activated carbon (AC) was prepared from waste walnut shells and characterized by Brunauer-Emmett-Teller (BET), field-emission scanning electron microscopy (FESEM), Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). For solutions containing PHE and Tween 80, the former was effectively removed and the latter could be economically recovered after adsorption by the prepared AC. The π-π interactions and oxygen containing functional groups of AC play important roles in the PHE adsorption process. The adsorption kinetics process could best be described using the pseudo-second-order model and adsorption isotherm results indicated that the Langmuir model best fitted the data. Adsorption thermodynamic parameters, including enthalpy change, Gibbs free energy change and entropy change were calculated. Under optimal conditions, PHE removal and Tween 80 recovery reached 95% and 90%, respectively. The results suggest that AC provided an efficient alternative for selective adsorption of PHE and recovery of Tween 80 after the soil washing processes. After adsorption AC could be regenerated with ethanol and even if AC were regenerated twice PHE removal reached 80%.