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Surface discharge plasma (SDP) combined with activated carbon (AC) was employed to eliminate dissolved organic matter from micro-polluted source water, with humic acid (HA) as the model pollutant. Synergistic effect on HA removal was observed in the SDP-AC system; HA removal efficiency reached 60.9% within 5-min treatment in the SDP-AC system with 5.0 g AC addition, whereas 16.7 and 17.4% of HA were removed in sole SDP system and AC adsorption, respectively. Scanning electron microscope and Boehm titration analysis showed that chemical reactions between active species and functional groups of AC occurred. The existence of isopropanol or benzoquinone exhibited inhibitive effects on HA removal in the SDP system, while these inhibitive effects were weakened in the SDP-AC system. The influences of AC on ozone equivalent concentration and HO concentration were evaluated, and there were approximately 39 and 20% decline in ozone equivalent concentration and HO concentration within 6-min treatment in the SDP-AC system, respectively, compared with those in the sole SDP system. Dissolved organic carbon, specific ultraviolet absorbance, and UV absorption ratios analysis demonstrated that the SDP treatment destroyed the chromophoric groups, double bonds, and aromatic structure of HA molecules, and these destructive actions were strengthened by AC. [ABSTRACT FROM AUTHOR]

Plasticizer pollution brought huge risks to ecological environment and human health. Surface discharge plasma (SDP) was employed to eliminate plasticizer in natural water, with dimethyl phthalate (DMP) as a typical plasticizer. Experimental results showed that DMP degradation efficiency reached 82.8% within 60 min’s SDP treatment, and the elimination process fitted well the first-order kinetic model. Low initial DMP concentration, alkaline condition, and low natural organic matter content were all conducive for DMP degradation. The contributions of OH radical and O 2 − to DMP elimination were 91.9% and 78.1%, respectively. Total organic carbon (TOC), UV–vis spectroscopy, and atomic force microscopy analysis demonstrated that DMP molecular structure was destroyed after the SDP treatment, and some small molecular fractions were generated. Approximately 47.8% of TOC and 73.5% of COD were eliminated after 60 min’s SDP treatment. Phthalic acid monomethyl ester, phthalic acid, o-phthalic anhydride, acetic acid, formic acid, and oxalic acid were detected as the byproducts. Carbon balance analysis among these intermediates showed that total carbon content was approximately 4.64 × 10 -2 mmol before treatment, and it was 4.578 × 10 -2 mmol after treatment, suggesting that some C-containing intermediates still existed but not detected. DMP degradation pathways in the SDP system were proposed. [ABSTRACT FROM AUTHOR]

Phthalates, as additives in the plastic production process, were able to enter the water environment, causing huge risks to ecological environment and human health. The potential of phthalates elimination in aqueous using sodium percarbonate (SPC) activated by discharge plasma (marked as “SPC + plasma”) was evaluated, with dimethyl phthalate (DMP) as a model pollutant. Experimental results showed that about 92.1% of DMP was eliminated in the “SPC + plasma” system with the treatment time of 30 min, which was 30.7% higher than that in sole plasma system, and the synergetic intensity for DMP elimination reached up to 127.0; and the energy yield was also raised by 131%. H 2 O 2 and OH radicals formation were promoted but ozone concentration decreased in the “SPC + plasma” system. Appropriate SPC dosage benefited DMP elimination, and the synergetic intensity increased from 2.0 to 127.0 as the SPC dosage increased from 0.06 mmol L −1 to 0.12 mmol L −1 . OH radicals, O 2 · − , 1 O 2 , and CO 3 · − played crucial roles in DMP elimination, and the roles of O 2 · − and 1 O 2 were strengthened in the “SPC + plasma” system. Ultraviolet–visible spectroscopy measurement, total content of organic carbon, atomic force microscopy and three-dimensional fluorescence analysis demonstrated that DMP molecular structure was destroyed during treatment, and some smaller molecular fractions were generated. The main intermediates included phthalic acid monomethyl ester, phthalic acid, o-phthalic anhydride, acetic acid, formic acid, and oxalic acid. The possible enhancement mechanisms for DMP elimination in the “SPC + plasma” system were proposed. [ABSTRACT FROM AUTHOR]

Humic acid (HA), a predominant type of natural organic matter in surface water, had several potential environmental and health risks. A gas phase surface discharge plasma system was employed to eliminate HA from micro-polluted surface water, and the effects of some concomitant inorganic ions on HA removal were evaluated. The experimental results showed that approximately 89.4% of HA could be smoothly eliminated after 40 min of the discharge plasma treatment, and the HA removal process could be fitted well by the first-order kinetic model. The presence of anions such as CO 3 2− and Cl − in the natural water were adverse for the HA removal due to their competition for the active species, whereas the effects of NO 3 − and SO 4 2− on the HA removal could be neglected; this deduction was also confirmed via the evolution of fluorescence spectra intensity of OH radicals. Although Cu 2+ could react with H 2 O 2 via Fenton-like reaction, its presence was still adverse for the HA removal due to the complexing effect of Cu 2+ with HA molecules. In addition, the HA removal processes were characterized by UV–Vis spectrum, DOC removal, specific absorbance parameters, and three-dimensional fluorescence spectrum analysis. [ABSTRACT FROM AUTHOR]

Humic acid (HA) was a predominant natural organic matter in ground water and surface waters. The removal of HA from micro-polluted source water using a gas phase surface discharge plasma at different grounding modes was studied, and three kinds of grounding modes (iron wire mesh, aluminized paper, and water) were selected. The experimental results illustrated that approximately 95.3% of HA in water was removed within 30 min’s discharge plasma treatment in the iron wire mesh electrode system, and it was 89.5% and 84.6% in the aluminized paper electrode system and water electrode system, respectively; although the strongest streamer discharge and the highest ozone equivalent concentration were both observed in the iron wire mesh electrode system. The discharge plasma treatment resulted in a relatively more homogeneous surface topography in the HA molecules as analyzed by scanning electron microscope (SEM), especially in the iron wire mesh electrode system and in the aluminized paper electrode system. The decomposition process of HA at different grounding modes was analyzed and compared via the evolution of the UV–Vis spectrum, dissolved organic carbon (DOC), specific ultraviolet absorbance (SUVA) and UV absorption ratios with treatment time. In addition, the HA removal efficacy in this study was comparable with those of some other techniques. [ABSTRACT FROM AUTHOR]

Degradation of humic acid (HA), a predominant type of natural organic matter in ground water and surface waters, was conducted using a gas phase surface discharge plasma system. HA standard and two surface waters (Wetland, and Weihe River) were selected as the targets. The experimental results showed that about 90.9% of standard HA was smoothly removed within 40 min's discharge plasma treatment at discharge voltage 23.0 kV, and the removal process fitted the first-order kinetic model. Roles of some active species in HA removal were studied by evaluating the effects of solution pH and OH radical scavenger; and the results presented that O 3 and OH radical played significant roles in HA removal. Scanning electron microscope (SEM) and FTIR analysis showed that HA surface topography and molecular structure were changed during discharge plasma process. The mineralization of HA was analyzed by UV–Vis spectrum, dissolved organic carbon (DOC), specific UV absorbance (SUVA), UV absorption ratios, and excitation-emission matrix (EEM) fluorescence. The formation of disinfection by-products during HA sample chlorination was also identified, and CHCl 3 was detected as the main disinfection by-product, but discharge plasma treatment could suppress its formation to a certain extent. In addition, approximately 82.3% and 67.9% of UV 254 were removed for the Weihe River water and the Wetland water after 40 min of discharge plasma treatment. [ABSTRACT FROM AUTHOR]

A gas phase surface discharge plasma combined with organic acids system was developed to enhance active species mass transfer and dye-containing wastewater treatment efficacy, with Acid Orange II (AO7) as the model pollutant. The effects of discharge voltage and various organic acid additives (acetic acid, lactic acid and nonoic acid) on AO7 decoloration efficiency were evaluated. The experimental results showed that an AO7 decoloration efficiency of approximately 69.0% was obtained within 4 min of discharge plasma treatment without organic acid addition, which was improved to 82.8%, 83.5% and 88.6% within the same treatment time with the addition of acetic acid, lactic acid and nonoic acid, respectively. The enhancement effects on AO7 decoloration efficiency could be attributed to the decrease in aqueous surface tension, improvement in bubble distribution and shape, and increase in ozone equivalent concentration. The AO7 wastewater was biodegradable after discharge plasma treatment with the addition of organic acid. AO7 decomposition intermediates were analyzed by UV–vis spectrometry and GC–MS; 2-naphthol, 1,4-benzoquinone, phthalic anhydride, coumarin, 1,2-naphthoquinone, and 2-formyl-benzoic acid were detected. A possible pathway for AO7 decomposition in this system was proposed. [ABSTRACT FROM AUTHOR]