Chunli Zheng

Adsorption behavior of Azo Dye C. I. Acid Red 14 in aqueous solution on surface soils

Azo dyes have received considerable attention because of their association with various human health problems. The aim of the investigation is to determine the adsorption behavior of azo dyes in aqueous solution on DG06, GSE17200, and GSE17201 soils using C. I. Acid Red 14 (AR14) as example. The experimental results indicate that the Freundlich model expresses the adsorption isotherm better than the Langmuir model and the pseudo-second-order model achieves adsorption of AR14 on the three soils well. Based on the pseudo-second-order model, the adsorption thermodynamic of AR14 on DG06 soil have been studied and the thermodynamics parameter of deltaG0 is determined and deltaG0 value shows the adsorption process of AR14 on DG06 is mainly physical in nature. Furthermore, the effects of temperature, pH and salinity (NaCl) on adsorption have been investigated. The decrease in pH or the increase in salinity enhances the adsorption of AR14 by DG06, GSE17200, and GSE17201.

Aerobic degradation of nitrobenzene by immobilization of Rhodotorula mucilaginosa in polyurethane foam.

Rhodotorula mucilaginosa Z1 capable of degrading nitrobenzene was immobilized in polyurethane foam. The nitrobenzene-degrading capacity of immobilized cells was compared to free cells in batches in shaken culture. Effects of pH and temperature on the nitrobenzene degradation showed that polyurethane-immobilized Z1 had higher tolerances toward acid, alkali, and heat than those of free cells. Kinetic studies revealed that higher concentrations of nitrobenzene were better tolerated and more quickly degraded by polyurethane-immobilized Z1 than by free cells. Moreover, the ability of polyurethane-immobilized Z1 to resist nitrobenzene shock load was enhanced. Experiments on the nitrobenzene degradation in different concentrations of NaCl and in the presence of phenol or aniline demonstrated that polyurethane-immobilized Z1 exhibited higher tolerance toward salinity and toxic chemicals than those of free cells. Immobilization therefore could be a promising method for treating nitrobenzene industrial wastewater. This is the first report on the degradation of nitrobenzene by a polyurethane-immobilized yeast strain.

Isolation and characterization of a novel nitrobenzene-degrading bacterium with high salinity tolerance: Micrococcus luteus.

Strain Z3 was isolated from nitrobenzene-contaminated sludge. Strain Z3 was able to utilize nitrobenzene as a sole source of carbon, nitrogen and energy under aerobic condition. Based on the morphology, physiological biochemical characteristics, and 16S rDNA sequence, strain Z3 was identified as Micrococcus luteus. Strain Z3 completely degraded nitrobenzene with initial concentration of 100, 150, 200, and 250 mg L(-1) within 70, 96, 120 and 196 h, respectively. Kinetics of nitrobenzene degradation was described using the Andrews equation. The kinetic parameters were as follows: q(max)=1.19 h(-1), K(s)=29.11 mg L(-1), and K(i)=94.00 mg L(-1). Strain Z3 had a high salinity tolerance. It degraded 200 mg L(-1) nitrobenzene completely in 5% NaCl (w/w%). Strain Z3 therefore could be an excellent candidate for the bio-treatment of nitrobenzene industrial wastewaters with high salinity. This is the first report on the degradation of nitrobenzene by M. luteus and the degradation of nitrobenzene achieved in such a high salinity.

Chemical profiles of urban fugitive dust PM2.5 samples in Northern Chinese cities

Urban fugitive dust PM2.5 samples were collected in 11 selected cities in North China, and 9 ions (SO4(2-), NO3(-), Cl(-), F(-), Na(+), NH4(+), K(+), Mg(2+), and Ca(2+)) and 22 elements (Si, Al, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Br, Rb, Sr, Sn, Sb, Ba, and Pb) were determined to investigate chemical profiles of PM2.5. The coefficient of divergence (CD) was used to compare the similarities of the chemical profiles for fugitive dust among three regions in North China, and the results showed that their composition are quite similar. Total water soluble ions occupied 9.3% and 10.0% on average of road dust and construction dust, respectively, indicating that most of the materials in urban fugitive dust samples were insoluble. Ca(2+) was the most abundant cation and SO4(2-) dominated in anions. Soil dust loading was calculated to occupy 70.8% and 83.6% in road dust and construction dust, respectively. Ca, Si, Fe, and Al were the most abundant elements in all the samples, and Ca was absolutely the most abundant specie among the 22 detected elements in construction dust samples. Chemical species ratios were used to highlight the characteristics of urban fugitive dust by comparing with other types of aerosols. High Ca/Al ratio was a good marker to distinguish urban fugitive dust from Asian dust and Chinese loess. In addition, low K(+)/K and NO3(-)/SO4(2-), and high Zn/Al and Pb/Al ratios were good indicators to separate urban fugitive dust from desert dust, Chinese loess, or urban PM2.5 samples.

Microscale spatial distribution and health assessment of PM2.5-bound polycyclic aromatic hydrocarbons (PAHs) at nine communities in Xi'an, China☆

Spatial variability of polycyclic aromatic hydrocarbons (PAHs) associated with fine particulate matter (PM2.5) was investigated in Xian, China, in summer of 2013. Sixteen priority PAHs were quantified in 24-h integrated air samples collected simultaneously at nine urban and suburban communities. The total quantified PAHs mass concentrations ranged from 32.4 to 104.7xa0ngxa0m-3, with an average value of 57.1xa0±xa023.0xa0ngxa0m-3. PAHs were observed higher concentrations at suburban communities (average: 86.3xa0ngxa0m-3) than at urban ones (average: 48.8xa0ngxa0m-3) due to a better enforcement of the pollution control policies at the urban scale, and meanwhile the disorganized management of motor vehicles and massive building constructions in the suburbs. Elevated PAH levels were observed in the industrialized regions (west and northwest of Xian) from Kriging interpolation analysis. Satellite-based visual interpretations of land use were also applied for the supporting the spatial distribution of PAHs among the communities. The average benzo[a]pyrene-equivalent toxicity (Σ[BaP]eq) at the nine communities was 6.9xa0±xa02.2xa0ngxa0m-3 during the sampling period, showing a generally similar spatial distribution to PAHs levels. On average, the excess inhalation lifetime cancer risk derived from Σ[BaP]eq indicated that eight persons per million of community residents would develop cancer due to PM2.5-bound PAHs exposure in Xian. The great in-city spatial variability of PAHs confirmed the importance of multiple points sampling to conduct exposure health risk assessment.

Treatment Technologies for Organic Wastewater

There are several contaminants in wastewater, with organic pollutants playing the major role. Many kinds of organic compounds, such as PCBs, pesticides, herbicides, phenols, polycylic aromatic hydrocarbons (PAHs), aliphatic and hetercyclic compounds are included in the wastewater, and industrial and agricultural production as well as the people living could be the source of organic wastewater endangering the safety of the water resource [1]. The wastewater of the farmland may contain high concentration of pesticides or herbicides; the wastewater of the coke plant may contain various PAHs; the wastewater of the chemical industry may contain various heterogeneity compounds, such as PCB, PBDE; the wastewater discharged by the food industry contains complex organic pollutants with high concentration of SS and BOD; and the municipal sewage contains different type of organic pollutants, such as oil, food, some dissolved organics and some surfactants. These organic pollutants in water can harm the environment and also pose health risks for humans.

Aerobic degradation of 2-picolinic acid by a nitrobenzene-assimilating strain: Streptomyces sp. Z2.

Streptomyces sp. Z2 was isolated from nitrobenzene contaminated activated sludge, which utilized nitrobenzene as a sole source of carbon, nitrogen, and energy under aerobic condition. It was found that besides nitrobenzene strain Z2 can degrade 2-picolinic acid. Strain Z2 completely degraded 2-picolinic acid with initial concentration of 500mg/L, 1000mg/L, 1500mg/L, 2000mg/L, 2500mg/L, and 3000mg/L within 36h, 50h, 72h, 100h, 136h, and 180h, respectively. Kinetics of 2-picolinic acid degradation was described using the Andrews equation. The kinetic parameters were as follows: q(max)=3.81h(-1), K(s)=83.10mg/L, and K(i)=252.11mg/L. During the biodegradation process, Z2 transformed 2-picolinic acid into a product which was identified as 6-hydroxy picolinic acid by UV-vis spectrometry, (1)H nuclear magnetic resonance spectroscopy, and mass spectrometry. 6-Hydroxy picolinic acid was then cleaved and mineralized with release of ammonia.

Sorption of Sulfadiazine, Norfloxacin, Metronidazole, and Tetracycline by Granular Activated Carbon: Kinetics, Mechanisms, and Isotherms

Activated carbon has widespread application in antibiotic-loaded wastewater treatment in recent years, owing to its developed pore structure, high superficies reactivity, and excellent mechanical and chemical stability. In this work, sorption experiments of four representative antibiotics, including sulfadiazine (SDZ), norfloxacin (NOR), metronidazole (MDE), and tetracycline (TC), over granular activated carbon (GAC), which was made from maize straw, were firstly studied. Kinetics, mechanism, and isotherm models related to the sorption process were employed. Results revealed that the sorption capacity by GAC followed the order SDZu2009>u2009NORu2009>u2009MDEu2009>u2009TC. The sorption kinetics of the four antibiotics well conformed to the pseudo-second-order model. Both the Weber-Morris intraparticle diffusion and Boyd kinetic models conveyed the information that film diffusion was dominant in the sorption process. The sorption isotherm was better fitted to the Langmuir model. This research may pave a basic way for removing antibiotics in municipal and industrial wastewater by activated carbon.

Decolorization of anthraquinone dye intermediate and its accelerating effect on reduction of azo acid dyes by Sphingomonas xenophaga in anaerobic–aerobic process

Decolorization of 1-aminoanthraquinone-2-sulfonic acid (ASA-2) and its accelerating effect on the reduction of azo acid dyes by Sphingomonas xenophaga QYY were investigated. The study showed that ASA-2 could be efficiently decolorized by strain QYY under aerobic conditions according to the analysis of total organic carbon removal and UV–VIS spectra changes. Moreover, strain QYY was able to reduce azo acid dyes under anaerobic conditions. The effects of various operating conditions such as carbon sources, temperature, and pH on the reduction rate were studied. It was demonstrated that ASA-2 used as a redox mediator could accelerate the reduction process. Consequently the reduction of azo acid dyes mediated by ASA-2 and the decolorization of ASA-2 with strain QYY could be achieved in an anaerobic–aerobic process.

Selective adsorption of metronidazole on conjugated microporous polymers

Conjugated microporous polymers (CMPs) have recently received extensive attention in oil/organic solvent-water separation field as a kind of ideal porous absorbents with tunable porosity, large surface areas, and super-hydrophobicity. However, reports on the application of CMPs in adsorption of hydrophilic contaminants from water are very few. In this work, we studied the adsorption of metronidazole (MNZ), a polar antibiotic, by two kinds of CMPs. The adsorption characteristics of MNZ by the CMPs, including adsorption kinetics, mechanism, and isotherm parameters were calculated. The adsorption kinetics of MNZ was well expressed by the pseudo-second-order model, and the adsorption process was found to be mainly controlled by film diffusion. The adsorption isotherm data agreed well with the Langmuir isotherm model, and the values of free energy E indicated that the adsorption nature of MNZ on the CMPs was physisorption. Increasing dispersion degree of the CMPs in MNZ solution resulted in greater adsorption. This work may provide fundamental guidance for the removal of antibiotics by CMPs.