Catalytic fast pyrolysis (CFP) of Kraft lignins with HZSM-5 zeolite for producing aromatics was investigated using analytical pyrolysis methods. Two Kraft lignins were fast pyrolyzed in the absence and presence of HZSM-5 in a Curie-point pyrolyzer. Without the catalyst, fast pyrolysis of lignin predominantly produced phenols and guaiacols that were derived from the subunits of lignin. However, the presence of HZSM-5 changed the product distribution dramatically. As the SiO2/Al2O3 ratio of HZSM-5 decreased from 200 to 25 and the catalyst-to-lignin ratio increased from 1 to 20, the lignin-derived oxygenates progressively decreased to trace and the aromatics increased substantially. The aromatic yield increased considerably as the pyrolysis temperature increased from 500°C to 650°C, but then decreased with yet further increase of pyrolysis temperature. Under optimal reaction conditions, the aromatic yields were 2.0 wt.% and 5.2 wt.% for the two lignins that had effective hydrogen indexes of 0.08 and 0.35.
Titanium dioxide is coated on the surface of MCM-41 wafer through the plasma enhanced chemical vapor deposition (PECVD) method using titanium isopropoxide (TTIP) as a precursor. Annealing temperature is a key factor affecting crystal phase of titanium dioxide. It will transform an amorphous structure to a polycrystalline structure by increasing temperature. The optimum anatase phase of TiO2 which can acquire the best methanol conversion under UV-light irradiation is obtained under an annealing temperature of 700°C for 2 h, substrate temperature of 500°C, 70 mL·min-1 of oxygen flow rate, and 100 W of plasma power. In addition, the films are composed of an anatase-rutile mixed phase, and the ratio of anatase to rutile varies with substrate temperature and oxygen flow rate. The particle sizes of titanium dioxide are between 30.3 nm and 59.9 nm by the calculation of Scherrer equation. Under the reaction conditions of 116.8 mg·L-1 methanol, 2.9 mg·L-1 moisture, and 75°C of reaction temperature, the best conversion of methanol with UV-light is 48.2% by using the anatase-rutile (91.3/8.7) mixed phase TiO2 in a batch reactor for 60 min. While under fluorescent light irradiation, the best photoactivity appears by using the anatase-rutile (55.4/44.6) mixed phase TiO2 with a conversion of 40.0%.
The residues of tetracycline antibiotics in water have attracted many concerns due to their harmful impact to human health. This paper reports an electrochemical sensor for the determination of tetracycline (TC) by the microelectrode, which was fabricated by electrodeposited gold colloids on tungsten tip. Cyclic voltammerty was used to study the electrochemical behavior of TC on the microelectrode. Well anodic wave was obtained at about 1.5 V in acidic solutions. Electrochemical determination of tetracycline was investigated using microelectrode by cyclic voltammetry. Under optimized conditions, the calibration curves for TC were obtained. The oxidation peak currents were linearly related to TC concentrations in the range of 1–10 mg·L-1 and 10–100 mg·L-1, respectively. The detection limit was 0.09 mg·L-1 (
Multi-walled carbon nanotubes (MWCNTs) were fabricated and oxidized by different concentrations of sodium hypochlorite (NaOCl) solutions. The untreated MWCNTs and modified MWCNTs were employed as adsorbents to study their characterizations and adsorption performance of toluene, ethylbenzene and xylene isomers (TEX) in an aqueous solution. The physicochemical properties of MWCNTs were greatly affected after oxidation, which influences TEX adsorption capacity. The 3% NaOCl-oxidized MWCNTs shows the greatest enhancement in TEX adsorption, followed by the 30% NaOCl. More interestingly, the 15% NaOCl-oxidized MWCNTs has lower adsorption capacities than untreated MWCNTs. The adsorption mechanism of TEX on treated MWCNTs is attributed to the combined action of hydrophobic interaction, π-π bonding interaction between the aromatic ring of TEX and the oxygen-containing functional groups of MWCNTs and electrostatic interaction. 3% NaOCl solution could not only introduce much oxygen-containing functional groups on MWCNTs, but also lead to less damage for the pore structure. This suggests that the CNTs-3% NaOCl is efficient adsorbent for TEX and that they may possess good potential for TEX removal in wastewater treatment.
Dissipation and plant uptake of polycyclic aromatic hydrocarbons (PAHs) in contaminated agricultural soil planted with perennial ryegrass were investigated in a field experiment. After two seasons of grass cultivation the mean concentration of 12 PAHs in soil decreased by 23.4% compared with the initial soil. The 3-, 4-, 5-, and 6-ring PAHs were dissipated by 30.9%, 25.5%, 21.2%, and 16.3% from the soil, respectively. Ryegrass shoots accumulated about 280 μg·kg-1, shoot dry matter biomass reached 2.48 × 104 kg·ha-1, and plant uptake accounted for about 0.99% of the decrease in PAHs in the soil. Significantly higher soil enzyme activities and microbial community functional diversity were observed in planted soil than that in the unplanted control. The results suggest that planting ryegrass may promote the dissipation of PAHs in long-term contaminated agricultural soil, and plant-promoted microbial degradation may be a main mechanism of phytoremediation.
Maintaining soil fertility, while controlling pollution from excessive chemical fertilizer application is important for keeping soil productivity of sustainable agriculture. Variety of straws have been used and proven to be good soil amendments for increasing soil organic matter (OM) and a range of additional soil nutrients. However, little is known about the utilization of cotton straw for soil amendment. To better understand the mechanism behind cotton straw soil amendments, investigations were performed upon cucumber seedlings, where changes to soil nutrients and microbial communities were investigated. The results revealed that the cotton straw application promoted the cucumber seedling growth by significantly increasing the soil OM, available nitrogen, available phosphorus, and available potassium. The concentration of cotton straw was positively correlated to both the number of the culturable microorganisms and also the total microbial biomass within soil. Furthermore, assessment of cotton straw application using Biolog metabolic profiling and phospholipid fatty acid analysis revealed that such application increased the microbial community metabolic activity, and markedly changed the structure of microbial community. 16S rRNA gene clone library construction and phylogenetic analysis of soil bacteria revealed
The actual harmful effects of industrial wastewater can not be reflected by the conventional water quality index. Therefore, the change in dissolved organic matter and the genetic toxicity of petrochemical wastewater were observed in the current study by examining the wastewater treatment plant of a large petrochemical enterprise in Northwest China. Using XAD-8, MSC, and DA-7 resins, the wastewater was separated into six fractions, namely, hydrophobic acid (HOA), hydrophobic neutral (HOB), hydrophobic alkaline, hydrophilic acid, hydrophilic alkaline, and hydrophilic neutral. Umu-test was used to detect the genetic toxicity of the wastewater samples, and fluorescence spectra were also obtained to examine genetic toxic substances. The results show that wastewater treatment facilities can effectively reduce the concentration of organic matter in petrochemical wastewater (
As an important type of emerging pollutants, ecological toxicity and risk of artificial musks are increasingly concerned. Thus, single and joint toxic effects of 1,3,4,6,7,8-hexahydro-4,6,6,7,8,8- hexamethylcyclopenta-gamma-2-benzopyran (HHCB) as one of the most widely applied artificial musks and cadmium (Cd) as an toxic metal on zebrafish (
Developing renewable energy is now becoming a hot topic as it is important in dealing with climate change issue and energy supply issue. With the growing demand of energy, it has become urgent to develop the effective policies and measures that would enable people to maintain the living standards. Among all the measures, price is an essential one. In order to evaluate the costs and prices of the electricity from renewable energy sources (RES-E) and their effects to the market, this paper firstly focus on the extra costs of the RES-E by breaking it into four parts, including investment, construction, connection and operation. Then, the policy choices made in some typical industrialized countries are examined to find answers to the problems RES-E can raise. Finally, the choices made in China are examined in comparison to industrialized countries so as to determine how the current situation could be improved.
This paper considers pollution density as a function of environmental investment. The higher environmental investment, the lower pollution density. The lower the pollution density is the higher production technology becomes. This is called the spillover effect. We collected China’s panel data at the provincial level from 2005 to 2009, and tested the spillover effect of environmental investment. This paper finds that the environmental investment influenced production technology positively. There is a significant positive relation between government expenditure and spillover effect.
The main purpose of this work is to investigate the characteristics of night soil and leaf co-composting using aerobic static composting method. Three influencing factors, including proportion of night soil and leaf, aeration rate and aeration pattern, were investigated through the evolution of the principal physicochemical properties, i.e., temperature, oxygen consumption rate, organic matters, moisture content, carbon, nitrogen, carbon-to-nitrogen ratio and Germination index (GI). It was found that the 3∶1 (w∶w) mixture of night soil and leaf was capable of achieving the highest composting temperature, longest retention time of high temperature (55°C), and fastest organic matter degradation. The 0.14 m3·min-1·m-3 aeration rate was most beneficial to composting, and the mixture of night soil and leaf maintained the highest temperature for the longest duration and achieved the highest CO2 content and GI. The continuous aeration pattern during composting was superior to an intermittent aeration pattern, since the latter delayed the composting process.
River waters in China have dual contamination by nutrients and recalcitrant organic compounds. In principle, the organic compounds could be used to drive denitrification of nitrate, thus arresting eutrophication potential, if the recalcitrant organics could be made bioavailable. This study investigated the potential to make the recalcitrant organics bioavailable through photocatalysis. Batch denitrification tests in a biofilm reactor demonstrated that dual-contaminated river water was short of available electron donor, which resulted in low total nitrogen (TN) removal by denitrification. However, the denitrification rate was increased significantly by adding glucose or by making the organic matters of the river water more bioavailable through photocatalysis. Photocatalysis for 15 min increased the Chemical Oxygen Demand (COD) of the river water from 53 to 84 mg·L-1 and led to a 4-fold increase in TN removal. The increase in TN removal gave the same effect as adding 92 mg·L-1 of glucose. During the photocatalysis experiments, the COD increased because photocatalysis transformed organic molecules from those that are resistant to dichromate oxidation in the COD test to those that can be oxidized by dichromate. This phenomenon was verified by testing photocatalysis of pyridine added to the river water. These findings point to the potential for N removal via denitrification after photocatalysis, and they also suggest that the rivers in China may be far more polluted than indicated by COD assays.
The cement-based solidification/stabilization (S/S) of nitrobenzene (NB) contaminated soils, with cement and lime as binders, sodium silicate solution and powder activated carbon (PAC) as additives, was optimized through an orthogonal experiment, and S/S efficiency was estimated by both leaching test and volatilization measurement. The leaching test results showed that the factors affecting S/S efficiency were NB concentration, cement-to-lime ratio and binder-to-soils ratio, in sequence. With increasing curing time, the leaching concentration of NB between different levels of the same factor in the orthogonal experiment decreased, and less than 9% NB leached out from the 28 d cured samples. The volatilization measurement results indicated that 0.5‰ of NB was volatilized during the mixing and curing processes for the samples without PAC in the 28 d cycle, whereas adding 2 wt% and 5 wt% PAC, with respect to the weight of contaminated soils, could reduce NB volatilization to half of its original values either during the mixing or curing process. The optimizing formula, that is, contaminated soils (dry weight):cement:lime= 100:25:25, with 5 wt% additional sodium silicate and 2 wt% additional PAC, was applied to the engineering application of NB contaminated soils. Both the leaching test results of the product and the ambient air quality monitoring results met related regulations during the treating process.