Bo Lai

Removal of high concentration p-nitrophenol in aqueous solution by zero valent iron with ultrasonic irradiation (US-ZVI)

In this study, the US-ZVI system was used to produce the strong reductants including H and nascent Fe(2+) ions to eliminate the toxicity of the high concentration p-nitrophenol (PNP) wastewater. The effect of the reactor structure, initial pH, ZVI dosage, ultrasonic power and initial PNP concentration on the removal efficiency of PNP from water was investigated intensively. The results show that a higher removal rate can be obtained by using a conical structure reactor, and the lower initial pH can aid the acceleration of PNP removal rate by using US-ZVI system. Furthermore, the removal efficiencies of PNP increased obviously with the increase of initial ZVI concentration from 0 to 15 gL(-1). Also, the treatment capacity of ZVI was enhanced remarkably by the ultrasonic irradiation, and the US-ZVI system can maintain high treatment efficiency for the high concentration PNP wastewater (500-10,000 mgL(-1)). Meanwhile, the high removal efficiency of PNP was mainly resulted from the synergistic reaction of ZVI and US. At last, the main degradation product (i.e., p-aminophenol) was detected by gas chromatography-mass spectrum (GC-MS). Thus, the reaction pathway of PNP in the US-ZVI system is proposed as a reducing process by the H and nascent Fe(2+) ions.

Comparative study on the reactivity of Fe/Cu bimetallic particles and zero valent iron (ZVI) under different conditions of N2, air or without aeration.

In order to further compare the degradation capacity of Fe(0) and Fe/Cu bimetallic system under different aeration conditions, the mineralization of PNP under different aeration conditions has been investigated thoroughly. The results show that the removal of PNP by Fe(0) or Fe/Cu system followed the pseudo-first-order reaction kinetics. Under the optimal conditions, the COD removal efficiencies obtained through Fe(0) or Fe/Cu system under different aeration conditions followed the trend that Fe/Cu (air)>Fe/Cu (N2: 0-30 min, air: 30-120 min)>control-Fe (air)>Fe/Cu (without aeration)>Fe/Cu (N2)>control-Fe (N2). It revealed that dissolved oxygen (DO) could improve the mineralization of PNP, and Cu could enhance the reactivity of Fe(0). In addition, the degradation of PNP was further analyzed by using UV-vis, FTIR and GC/MS, and the results suggest that Fe/Cu bimetallic system with air aeration could completely break the benzene ring and NO2 structure of PNP and could generate the nontoxic and biodegradable intermediate products. Meanwhile, most of these intermediate products were further mineralized into CO2 and H2O, which brought about a high COD removal efficiency (83.8%). Therefore, Fe/Cu bimetallic system with air aeration would be a promising process for toxic refractory industry wastewater.

Comprehensive analysis of the toxic and refractory pollutants in acrylonitrile-butadiene-styrene resin manufacturing wastewater by gas chromatography spectrometry with a mass or flame ionization detector

Acrylonitrile-butadiene-styrene (ABS) resin manufacturing wastewater is a complicated, toxic and refractory industrial wastewater. Comprehensive and accurate analysis of the typical pollutants in ABS resin manufacturing wastewater is critical to develop cost-effective wastewater treatment technologies. In this paper, a comprehensively qualitative analysis combined with three complementary methods has been developed for the detection of typical pollutants in ABS resin manufacturing wastewater from three production sections, and thirty-seven compounds had been detected and further confirmed by this analysis method with standards. Simultaneous chromatographic separation and quantification of seven representative pollutants, including three mononuclear aromatics, three acrylonitrile dimers and one acrylonitrile derivative, were achieved by GC-FID system. The detection limits of this method for seven representative pollutants were in the range of 0.007-0.89 mg/L. The within-day and between-day precisions of this method were less than 6.5% (RSD, n=6). The recoveries of the representative pollutants reached 90-120%. The ABS resin manufacturing wastewater from E zone was successfully determined by this method, with two mononuclear aromatics and three acrylonitrile dimers accounting for 57.73% and 40.63% of the selected seven compounds, respectively. These results reveal that the removal of mononuclear aromatics and acrylonitrile dimers is a key to treat this wastewater.

Treatment of reverse osmosis (RO) concentrate by the combined Fe/Cu/air and Fenton process (1stFe/Cu/air-Fenton-2ndFe/Cu/air).

To decompose or transform the toxic and refractory reverse osmosis (RO) concentrate and improve the biodegradability, 1stFe/Cu/air-Fenton-2ndFe/Cu/air were developed to treat RO concentrate obtained from an amino acid production plant in northern China. First, their operating conditions were optimized thoroughly. Furthermore, 5 control experiments were setup to confirm the superiority of 1stFe/Cu/air-Fenton-2ndFe/Cu/air and synergistic reaction between Fe/Cu/air and Fenton. The results suggest that the developed method could obtain high COD removal (65.1%) and BOD5/COD ratio (0.26) due to the synergistic reaction between Fe/Cu/air and Fenton. Under the optimal conditions, the influent and effluent of 1stFe/Cu/air-Fenton-2ndFe/Cu/air and 5 control experiments were analyzed by using UV, FTIR, EEM and LC, which confirm the superiority of 1stFe/Cu/air-Fenton-2ndFe/Cu/air. Therefore, the developed method in this study is a promising process for treatment of RO concentrate.

Application of excitation and emission matrix fluorescence (EEM) and UV-vis absorption to monitor the characteristics of Alizarin Red S (ARS) during electro-Fenton degradation process.

Oxidative degradation of Alizarin Red S (ARS) in aqueous solutions by using electro-Fenton was studied. At first, effect of operating parameters such as current density, aeration rate and initial pH on the degradation of ARS were studied by using UV-vis spectrum, respectively. Then, under the optimal operating conditions (current density: 10.0mAcm(-2), aeration rate: 1000mLmin(-1), initial pH: 2.8), the identification of degradation products of ARS was carried out by using GC-MS and HPLC, meanwhile its degradation pathway was proposed according to the intermediates. Considering the location, intensity and intensity ratio of fluorescence center peak of the ARS in aqueous solution, a convenient and quick monitoring method by using excitation-emission matrix fluorescence spectrum technology was developed to monitor the degradation degree of ARS through electro-Fenton process. Furthermore, it is suggested that the developed method would be promising for the quick analysis and evaluation of the degradation degree of the pollutants with π-conjugated system.

Removal of FePO4 and Fe3(PO4)2 crystals on the surface of passive fillers in Fe0/GAC reactor using the acclimated bacteria

As past studies presented, there is obvious defect that the fillers in the Fe(0)/GAC reactor begin to be passive after about 60 d continuous running, although the complicated, toxic and refractory ABS resin wastewater can be pretreated efficiently by the Fe(0)/GAC reactor. During the process, the Fe(3)(PO(4))(2) and FePO(4) crystals with high density in the passive film are formed by the reaction between PO(4)(3-) and Fe(2+)/Fe(3+). Meanwhile, they obstruct the formation of macroscopic galvanic cells between Fe(0) and GAC, which will lower the wastewater treatment efficiency of Fe(0)/GAC reactor. In this study, in order to remove the Fe(3)(PO(4))(2) and FePO(4) crystals on the surface of the passive fillers, the bacteria were acclimated in the passive Fe(0)/GAC reactor. According to the results, it can be concluded that the Fe(3)(PO(4))(2) and FePO(4) crystals with high density in the passive film could be decomposed or removed by the joint action between the typical propionic acid type fermentation bacteria and sulfate reducing bacteria (SRB), whereas the PO(4)(3-) ions from the decomposition of the Fe(3)(PO(4))(2) and FePO(4) crystals were released into aqueous solution which would be discharged from the passive Fe(0)/GAC reactor. Furthermore, the remained FeS and sulfur (S) in the passive film also can be decomposed or removed easily by the oxidation of the sulfur-oxidizing bacteria. This study provides some theoretical references for the further study of a cost-effective bio-regeneration technology to solve the passive problems of the fillers in the zero-valent iron (ZVI) or Fe(0)/GAC reactor.

Comparative study on the characteristics, operational life and reactivity of Fe/Cu bimetallic particles prepared by electroless and displacement plating process

In this study, an electroless (electrode-less) copper plating technology was developed to prepare the high-reactive and robust iron–copper (Fe/Cu) bimetallic particles. First, effect of pretreatment and key preparation parameters (e.g., complexant, H3BO3, NiSO4·7H2O, pH and plating time) on the reactivity of Fe/Cu bimetallic particles were investigated, respectively. Their reactivity was evaluated according to the obtained Kobs for PNP removal. Also, the characteristics of Fe/Cu bimetallic particles prepared by electroless plating and displacement plating were comparatively observed by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The analysis results show that when Fe/Cu bimetallic particles were prepared by electroless plating, copper was uniformly deposited on the surface of Fe0 substrate, and only a few bulky particles were observed. However, plenty of loose copper blocks were heterogeneously distributed on the surface of Fe0 substrates when the Fe/Cu bimetallic particles were prepared by the conventional displacement plating. Furthermore, the operational life and reactivity of Fe/Cu bimetallic particles prepared by electroless and displacement plating process were comparatively investigated by the recycling experiment. The results suggest that the new Fe/Cu bimetallic particles have a longer operational life than that of the conventional Fe/Cu bimetallic particles. Meanwhile, it can be seen from the control experiments that the new Fe/Cu bimetallic particles have a stronger reactivity for the PNP removal both in Fe/Cu/air and Fe/Cu/N2 processes. As results, the new electroless plating for the preparation of Fe/Cu bimetallic particles is superior to the conventional displacement plating. In other words, the electroless copper plating is a promising technology to prepare the high-reactive and robust Fe/Cu bimetallic particles.

Fe0 and Fe0 fully covered with Cu0 (Fe0 + Fe/Cu) in a fixed bed reactor for nitrate removal

To develop a cost-effective, feasible and robust technology for nitrate removal by chemical degradation, a Fe0 and Fe0 fully covered with Cu0 (i.e., Fe0 + Fe/Cu) fixed reactor was set up in this study. The performance and mechanism of the Fe0 + Fe/Cu system for nitrate reduction were investigated thoroughly. First, the initial pH of the solution and the mass ratio of Fe0 and Fe/Cu (i.e., M(Fe0)/M(Fe/Cu) ratio) in the medium materials were optimized, and then two control experiments (Fe0 + quartz sand system and Fe0 + Cu0 system) were set up to confirm the superiority of the Fe0 + Fe/Cu system. The results suggest that high NO3−–N removal (>99.0%), Kobs (0.403 min−1) and low NH4+–N generation rate (61.1%) could be obtained by the developed system (Fe0 + Fe/Cu) with a short hydraulic retention time (HRT = 16 min). In addition, the operational life of the Fe0 + Fe/Cu system and Fe0 + quartz sand system were investigated comparatively, which shows that the operational life of the former was much longer than that of the latter. Finally, characteristics of the medium materials in the Fe0 + Fe/Cu system and Fe0 + quartz sand system were also observed by scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) before and after long-term operation. Therefore, the developed system in this study is a promising technology for nitrate contaminated water treatment.

Mineralization of ammunition wastewater by a micron-size Fe0/O3 process (mFe0/O3)

A micron-size Fe0/O3 process (mFe0/O3) was set up to mineralize the pollutants in ammunition wastewater, and its key operational parameters (e.g., initial pH, ozone flow rate, and mFe0 dosage) were optimized by the batch experiments, respectively. Under the optimal conditions, COD removal efficiency obtained by the mFe0/O3 process (i.e., 92.6% after 30 min treatment) was much higher than those of ozone alone (46.5%), mFe0 alone (38.3%) or mFe0/air (58.5%), which confirm the synergetic effect between mFe0 and ozone. In addition, the BOD5/COD (B/C) ratio was elevated from 0 to 0.54 after 30 min treatment by the mFe0/O3 process, which indicates the significant improvement of biodegradability. Furthermore, the analysis results of the UV-vis and excitation–emission matrix (EEM) fluorescence spectra further confirm that the toxic and refractory pollutants in ammunition wastewater had been completely decomposed or transformed into smaller molecule organic compounds. Meanwhile, the superiority of the mFe0/O3 process has been confirmed according the analysis results of COD removal, B/C ratio, UV-vis and EEM. Therefore, the mFe0/O3 process could be proposed as a promising treatment technology for toxic and refractory ammunition wastewater.

Passivation process and the mechanism of packing particles in the Fe0/GAC system during the treatment of ABS resin wastewater.

This study provides mechanistic insights into the passivation of the packing particles during the treatment of acrylonitrile–butadiene–styrene (ABS) resin wastewater by the Fe0/GAC system. The granular-activated carbon (GAC) and iron chippings (Fe0) were mixed together with a volumetric ratio of 1:1. GAC has a mean particle size of approximately 3–5 mm, a specific surface of 748 m2 g−1, a total pore volume of 0.48 mL g−1 and a bulk density of 0.49 g cm−3. The iron chippings have a compact and non-porous surface morphology. The results show that the packing particles in the Fe0/GAC system would lose their activity because the removal of TOC and for ABS resin wastewater could not carried out by the Fe0/GAC system after 40 days continuous running. Meanwhile, the availability of O2 and intrinsic reactivity of Fe0 play a key role on the form of passive film with different iron oxidation states. The passive film on the surface of iron chippings was formed by two phases: (a) local corrosion phase (0–20 d) and (b) co-precipitation phase (20–40 d), while that of GAC was mainly formed by the co-precipitation of corrosion products with and because and would not easily reach the Fe0 surface. Therefore, in order to avoid the occurrence of filler passivation, high concentrations of and in wastewater should be removed before the treatment process of the Fe/GAC system.