Chromate reduction on humic acid derived from a peat soil--exploration of the activated sites on HAs for chromate removal

Humic substances are a major component of soil organic matter that influence the behavior and fate of heavy metals such as Cr(VI), a toxic and carcinogenic element. In the study, a repetitive extraction technique was used to fractionate humic acids (HAs) from a peat soil into three fractions (denoted as F1, F2, and F3), and the relative importance of O-containing aromatic and aliphatic domains in humic substances for scavenging Cr(VI) was addressed at pH 1. Spectroscopic analyses indicated that the concentrations of aromatic C and O-containing functional groups decreased with a progressive extraction as follows: F1>F2>F3. Cr(VI) removal by HA proceeded slowly, but it was enhanced when light was applied due to the production of efficient reductants, such as superoxide radical and H(2)O(2), for Cr(VI). Higher aromatic- and O-containing F1 fraction exhibited a greater efficiency for Cr(VI) reduction (with a removal rate of ca. 2.89 mmol g(-1) HA under illumination for 3 h). (13)C NMR and FTIR spectra further demonstrated that the carboxyl groups were primarily responsible for Cr(VI) reduction. This study implied the mobility and fate of Cr(VI) would be greatly inhibited in the environments containing such organic groups.     

Brownfield Sites Remediation Technology Overview,Trends, and Opportunities in China

Over decades of economic development, China's industrialization has led to significant environmental issues due to unregulated discharges into air, water, and soil. As cities continue to expand (i.e., urbanization trend) and awareness/concerns about environmental pollution rises, many industrial facilities along the edge of or within the city boundaries have been relocated or closed. This urbanization trend leaves behind idled and abandoned land that is contaminated from the former industrial activities and unregulated discharges. China released its first nationwide soil quality survey in April 2014, and the survey suggests that soil conditions in China represent a significant challenge. China has encouraged local engineering firms to demonstrate soil treatment technologies through pilot‐scale studies, but the outcomes of many demonstrations have not been promising due to the lack of remediation experience and underdeveloped technical guidelines that are needed to guide the remediation processes. During the past decade, some local soil remediation experience has been established, but it is limited for certain technologies that address their primary contaminants of concern: heavy metals and persistent organic pollutants. In 2014, national technical guidelines were published regarding environmental investigation, risk assessment, monitoring, and remediation; however, regulations and funding systems are still underdeveloped. Thus, the remediation processes that should maximize economic and environmental benefits are not streamlined. This article provides an overview of the latest regulatory developments, remediation technologies applied, technology trends, and market opportunities in China. The provided information aims to allow international remediation practitioners to better understand and appreciate this unique and emerging remediation market, which is growing fast, and to highlight the importance of developing a sustainable model that not only provides for cleanup of the environment but also supports economic development. ©2015 Wiley Periodicals, Inc.     

Ambient Air Particulates Bound Mercury Hg(p) Study Among Four Crops (Rice,White Cabbage,Arden Lettuce,and Gynura) at a Characteristic Sampling Site

The main purpose of this study was to monitor ambient air particulates and particulate-bound Hg (Hg[p]) compositions in different crops in the coastal zone in the Taichung, Taiwan, area at a sampling site during 2013 October to 2013 December. In addition, a direct mercury analyzer (DMA-80) was used to directly detect the concentration with measured results by the regression equation of Hg in the ambient air. The results indicated that: 1) the mean values of ambient air Hg(p) compositions in rice displayed no significant differences for weeks one, two, and three versus those of the other crops (white cabbage, Arden lettuce, and Gynura procumbens); 2) for white cabbage, the higher the humidity, the lower the average ambient air Hg(p) compositions that were obtained, a phenomenon that was also reflected on the crops of white cabbage and G. procumbens; 3) Arden lettuce displayed no significant differences in the leaf Hg(p) compositions during weeks one, two, and three; however, the stem portions displayed significant differences in Hg(p) compositions during weeks two and three; and 4) the Spearman statistical method showed the mean differences for ambient air Hg(p) at the Long-jing sampling site (coastal regions) with four different crops (rice, white cabbage, Arden lettuce, and Gynura) in central Taiwan. The results further revealed no significant differences in mean values.     

Anaerobic degradation of nonylphenol in soil

This study investigated the effects of various factors on the anaerobic degradation of nonylphenol (NP) in soil. The results show that the optimal pH for NP degradation was 7.0 and that the degradation rate was enhanced when the temperature was increased. The addition of compost enhanced NP degradation. The individual addition of the electron donors lactate, acetate, and pyruvate inhibited NP degradation. The high-to-low order of NP degradation rates under three anaerobic conditions was sulfate-reducing conditions > methanogenic conditions > nitrate-reducing conditions. The results show that sulfate-reducing bacteria, methanogen, and eubacteria are involved in the anaerobic degradation of NP, with sulfate-reducing bacteria being a major component of the soil. Of the anaerobic strains isolated from the soil samples, strain AT3 expressed the best ability to biodegrade NP.     

Characteristics of exhaust gas,liquid products,and residues of printed circuit boards using the pyrolysis process

Introduction  

The pyrolytic method was employed to recycle metals and brominated compounds blended into printed circuit boards (PCBs).     

Quantifying the waste reduction potential of using prefabrication in building construction in Hong Kong

As Hong Kong is a compact city with limited available land and high land prices, the construction of high-rise buildings is prevalent. The construction industry produces a significant amount of building waste. In 2005, about 21.5 million tonnes of construction waste were generated, of which 11% was disposed of in landfills and 89% in public filling areas. At the present rate, Hong Kong will run out of both public filling areas and landfill space within the next decade. The government is taking action to tackle the problem, such as by introducing a construction waste landfill charge, and promoting prefabrication to reduce on-site waste generation. This paper reports an ongoing study on the use of prefabrication in buildings and its impact on waste reduction in Hong Kong. A questionnaire survey was administered to experienced professionals, and case studies of recently completed building projects were conducted. The results revealed that construction waste reduction is one of the major benefits when using prefabrication compared with conventional construction. The average wastage reduction level was about 52%. This implies that a wider use of prefabrication could considerably reduce construction waste generation in Hong Kong and alleviate the burdens associated with its management.     

The mechanisms of arsenic removal from soil by electrokinetic process coupled with iron permeable reaction barrier

An innovative remediation system of electrokinetic process coupled with permeable reaction barrier (PRB) was proposed for arsenic removal in soil matrix. Batch tests with PRB media of Fe(0) and FeOOH under potential gradient of 2 V cm(-1) for 5d duration were conducted to evaluate the removal mechanisms of arsenic. Arsenic enhancement of 1.6-2.2 times was achieved when a PRB system was installed in an electrokinetic system. A best performance was found in system with FeOOH layer located in the middle of elctrokinetic cell. This was largely because of higher surface area of FeOOH and the moving of HAsO(4)(2-) to the anode side by electromigration effect was inhibited by the electroosmosis flow. The surface characteristics of PRB media, which were qualified by SEM coupled with energy dispersive spectroscopy (EDS), were clearly confirmed that arsenic was found on the passive layer surface. Results indicated that the removal of As in EK/PRB systems was much more contributed by surface adsorption/precipitation on PRB media than by EK process. Furthermore among the electrical removal mechanisms, electromigration was predominant than electrosmotic flow. Surface adsorption and precipitation were respectively the principal removal mechanism under acid environment, e.g. near anode side, and under basic environment, e.g. near cathode side. The results reported in the present work will be beneficial to optimizing design of batch EK/PRB system and enlarging to the field scale system.     

Silane removal at ambient temperature by using alumina-supported metal oxide adsorbents

Copper, zinc, and cerium oxide adsorbents supported on alumina were used to remove silane gas (SiH4). The adsorbents were prepared using a coprecipitation method and characterized by the inductively coupled plasma mass spectrometry, X-ray powder diffractometer, and Brunauer-Emmett-Teller method (BET). The silane removal efficiency and adsorption capacity of the adsorbents were investigated in this study. Test results showed that the adsorbents containing active species had a removal efficiency >99.9% for SiH4 before breakthrough. Adsorbents containing mixed oxides (CuO-CeO2/ Al2O3 and CuO-ZnO/Al2O3), which showed well-dispersed active species and high BET surface areas, had a greater adsorption capacity than the adsorbents containing single metal oxide. However, when the CuO-ZnO/ Al2O3 adsorbents contain >40 wt% of active metal oxides, the increase of active species lowered the BET surface area leading to a decrease of the adsorption capacity. Additionally, when the content of the active metal oxides was between 20% and 40%, the CuO-ZnO/Al2O3 adsorbents demonstrated higher adsorption capacity.     

Effect of recycle-to-influent ratio on activities of nitrifiers and denitrifiers in a combined UASB-activated sludge reactor system

A laboratory study using a combined upflow anaerobic sludge bed (UASB)-activated sludge (AS) reactor system was undertaken to explore the effect of recycle-to-influent ratio (R(e)=1, 2, and 3) on the activities of nitrifiers and denitrifiers. Suspended-solids pre-settled piggery wastewater was used as the substrate-feed wastewater. At the R(e) of 1-3, the combined reactor system achieved efficient removal of COD (96-97%), TKN (100%) and total nitrogen TN (54-77%). Methanogenesis occurred with nearly-complete denitrification in the UASB reactor, whereas complete nitrification took place in the AS reactor. A higher R(e) (i.e., accompanied with a shorter solids retention time) resulted in a larger amount of high-activity denitrifiers and thereby achieved a higher TN removal efficiency. Compact granules and a high biomass concentration in the UASB reactor were observed. At the R(e) of 1-3, the maximum specific reaction rate of nitrifiers (0.45-0.49 NH(4)(+)-NmgVSS(-1)d(-1)) and the specific nitrification rates of mixed culture (0.18-0.22mg NH(4)(+)-NmgVSS(-1)d(-1)) in the AS reactor varied slightly; whereas the maximum specific reaction rate of denitrifiers (0.18-0.27mg NO(x)(-)-NmgVSS(-1)d(-1)) and the specific denitrification and COD removal rates of mixed culture (0.025-0.050mg NO(x)(-)-NmgVSS(-1)d(-1); 0.24-0.31mgCODmgVSS(-1)d(-1)) in the UASB reactor increased with increasing R(e). The primary finding of the study is that the combined UASB-AS reactor system should be operated at a higher R(e) to maintain high-activity denitrifiers to remove organic materials and nitrogen from piggery wastewater.     

Controlled release fertilizers (CRFs) for climate-smart agriculture practices: a comprehensive review on release mechanism,materials, methods of preparation,and effect on environmental parameters

Environmental Science and Pollution Research - Fertilizers play an essential role in increasing crop yield, maintaining soil fertility, and provide a steady supply of nutrients for plant...