Abstract
The electro-Fenton (EF) process was applied to treat mother liquor of gas field wastewater (ML-GFW). The Fe-Fe electrodes were used and H2O2 was added to the EF system. Effect of initial pH on chemical oxygen demand (COD) removal efficiency, specific electrical energy consumption (SEEC), specific electrode plate consumption (SEPC) and organic matter removal mechanism was investigated. The results showed that COD removal efficiency reached the maximum (71.9%) at initial pH of 3 after reaction for 3 h. Besides, considering with the SEEC and SEPC, pH of 3 was also the best choice, at which SEEC was 4.7 kW h kgCOD−1, SEPC was 0.82 kgFe kgCOD−1. Organic matter removal was achieved by two ways: oxidation and flocculation, and oxidation played a major role. With the analysis of GC-MS, the possible degradation pathways of the representative contaminants in the ML-GFW were given.
Highlights
In recent years, the consistently high growth rate of Chinese economy is supported by energy consumption which is heavily dependent on oil-based resources [1,2]
The pH in the EF process can control the activity of oxidant and substrate, speciation factor of iron and H2O2 so that it can be considered as a pH-dependent process [13]
The amount of HCOÀ3 in the mother liquor of gas field wastewater (ML-GFW) was 2.84 × 103 mg l−1 in table 1, and the buffering capacity of HCOÀ3 was of great influence to the experiment, because it contributed to the stabilization of H2O2 and resulted in prolonged reactivity [19]
Summary
The consistently high growth rate of Chinese economy is supported by energy consumption which is heavily dependent on oil-based resources [1,2]. Gas field wastewater treatment technologies include physical methods, biological methods and physico-chemical methods mainly. The applications of the biological treatments on gas field wastewater are often challenged by poor load and impact resistance ability, and microbes are sensitive to the toxicity of pollutants in the wastewater [6]. Regarding physico-chemical methods, advanced oxidation processes (AOPs) are effective for the treatment of wastewater that contains non-biodegradable, inhibitory or toxic compounds [7] such as the gas field wastewater. AOPs can be classified into four categories: homogeneous chemical oxidation (H2O2/Fe2+ and H2O2/O3), photocatalytic processes (H2O2/UV and TiO2/UV), sonochemical oxidation and electro-chemical oxidation [8]. As one of the most efficient electro-chemical oxidation treatments, the application of electro-Fenton (EF) processes for gas field wastewater treatment is still limited
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