Determinants of nitrous oxide emission from agricultural drainage waters

Emissions of the powerful greenhouse gas nitrous oxide (N₂O) from agricultural drainage waters are poorly quantified and its determinants are not fully understood. Nitrous oxide formation in agricultural soils is known to increase in response to N fertiliser application, but the response of N₂O in field drainage waters is unknown. This investigation combined an intensive study of the direct flux of N₂O from the surface of a fertilised barley field with measurement of dissolved N₂O and nitrate (NO₃) concentrations in the same field’s drainage waters. Dissolved N₂O in drainage waters showed a clear response to field N fertilisation, following an identical pattern to direct N₂O flux from the field surface. The range in N₂O concentrations between individual field drains sampled on the same day was large, indicating considerable spatial variability exists at the farm scale. A consistent pattern of very rapid outgassing of the dissolved N₂O in open drainage ditches was accentuated at a weir, where increased turbulence led to a clear drop in dissolved N₂O concentration. This study underlines the need for carefully planned sampling campaigns wherever whole farm or catchment N₂O emission budgets are attempted. It adds weight to the argument for the downward revision of the IPCC emission factor (EF₅-g) for NO₃ in drainage waters.     

Determinants of nitrous oxide emission from agricultural drainage waters

Emissions of the powerful greenhouse gas nitrous oxide (N₂O) from agricultural drainage waters are poorly quantified and its determinants are not fully understood. Nitrous oxide formation in agricultural soils is known to increase in response to N fertiliser application, but the response of N₂O in field drainage waters is unknown. This investigation combined an intensive study of the direct flux of N₂O from the surface of a fertilised barley field with measurement of dissolved N₂O and nitrate (NO₃) concentrations in the same fields drainage waters. Dissolved N₂O in drainage waters showed a clear response to field N fertilisation, following an identical pattern to direct N₂O flux from the field surface. The range in N₂O concentrations between individual field drains sampled on the same day was large, indicating considerable spatial variability exists at the farm scale. A consistent pattern of very rapid outgassing of the dissolved N₂O in open drainage ditches was accentuated at a weir, where increased turbulence led to a clear drop in dissolved N₂O concentration. This study underlines the need for carefully planned sampling campaigns wherever whole farm or catchment N₂O emission budgets are attempted. It adds weight to the argument for the downward revision of the IPCC emission factor (EF₅-g) for NO₃ in drainage waters.     

Chromium removal from groundwater using simple physical/chemical treatment

Groundwater at a Superfund site in west Texas has been found to contain chromium at concentrations exceeding EPA's drinking water standard of .05 mg/l. Alternative treatment methods for this site were investigated; this article presents the evaluation of a physicochemical treatment system, in which removal of total chromium to levels below the drinking water standard was achieved through reduction of hexavalent chromium and subsequent removal by coprecipitation with iron. Costs for the construction of the pilot and full-scale systems are also discussed.     

L-谷氨酸改性氧化石墨烯对Cu2+的吸附

采用L-谷氨酸（L-Glu）改性氧化石墨烯（GO）制备吸附剂L-Glu/GO,并进行了XRD、FTIR和SEM表征。考察了不同因素对L-Glu/GO吸附Cu²⁺的影响,并对L-Glu/GO的吸附-解吸能力进行了研究。实验结果表明：L-Glu/GO对Cu²⁺的吸附在10 min内就可达到吸附平衡;在Cu²⁺初始质量浓度为70 mg/L、初始pH为5、L-Glu/GO投加量为0.200 g/L、吸附时间为120 min、吸附温度为30 ℃的条件下,L-Glu/GO的最大吸附量可达292.460 mg/g。准二级动力学和Langmuir模型能很好地拟合此吸附过程,且显示该吸附过程可促进L-Glu/GO对Cu²⁺的吸附。热力学研究结果表明该吸附过程是一个自发的放热过程。经过5次吸附-解吸循环后,L-Glu/GO对Cu²⁺的吸附率仍在92%以上,表明该吸附剂再生性好,可重复使用。     

钢渣净化水中磷素的研究进展

在对国内外钢渣除磷研究现状进行总结的基础上,介绍了铜渣的组成及其物理、化学性质,并进一步阐述了其在除磷过程中涉及到的反应机理,提出了钢渣应用于含磷废水处理时存在的问题及今后的研究发展方向。     

Ammonium removal from landfill fresh leachate using zeolite as adsorbent

Journal of Material Cycles and Waste Management - In this study, the effect of natural zeolite on the ammonium ion removal from landfill fresh leachate (LFL) was investigated. The effect of...     

Pyrolysis of low-density polyethylene using synthetic catalysts produced from fly ash

Catalytic pyrolysis of low-density polyethylene (LDPE) was investigated using various fly ash-derived silica–alumina catalysts (FSAs). FSAs were prepared by a simple activation method that basically includes NaOH treatment of fly ash by a fusion method, followed by an aging process. A series of LDPE pyrolysis experiments was conducted and the catalytic performance of FSAs was assessed in terms of the degradation temperature and the simulated boiling point distribution of the liquid products. The effects of synthesis conditions such as NaOH/fly ash weight ratio and aging time were examined by X-ray diffractometer (XRD), Brunauer-Emmett-Teller (BET) surface area analyzer, and scanning electron microscope to clarify the controlling factors affecting the catalytic activity. To obtain catalyst with high activity, it is necessary to produce sufficient silica and alumina species that can be easily co-precipitated into solid acid catalyst by destruction of the fly ash structure and to optimize the activation time for catalyst synthesis to prevent the transformation into inactive phases. The catalytic performance of FSA obtained from optimal conditions was equivalent to that of commercial catalysts, demonstrating the effectiveness of the catalyst.     

Removal of Reactive Blue 19 dye from synthetic wastewater using UV/H2O2 and UV/Cl advanced oxidation processes

The textile and dyeing industries are among the largest water-consuming and polluting industries in the world. The most important feature of the textile dyeing industry wastewater is its color, due to the use of colored materials. Most of these dye compounds are resistant to conventional purification methods and their biodegradation is very low through secondary purification processes, resulting in incomplete removal. Therefore, selecting the optimal method to remove these color compounds is essential. In this study, we studied the removal of an organic dye contaminant (Reactive Blue dye 19 [RB19]) using advanced oxidation processes (AOPs). For this purpose, ultraviolet (UV) mercury lamps with a wavelength of 254 nm and a voltage of W16 inside a reactor were used as an energy source. The experiments were performed in a collimated beam reactor inside a dark chamber. Two oxidizers, sodium hypochlorite (NaOCl) and hydrogen peroxide (H₂O₂), were used to remove RB19 from the artificial sewage stream. Removal of RB19 with a concentration of 20 mg/L with variable pH (5, 7, and 9), oxidant concentrations (5, 10, and 20 mg/L), and time (5, 10, 15, and 30 min) were investigated during the processes of photolysis, chemical oxidation (by H₂O₂ and NaOCl), and UV/NaOCl and UV/H₂O₂ AOPs. The photolysis process did not remove the RB19. The highest removal efficiencies of RB19 by chemical oxidation processes with NaOCl and H₂O₂, UV/NaOCl, and UV/H₂O₂ at optimal conditions (pH = 5, [oxidant] = 20 mg/L, RB19 = 20 mg/L, and radiation intensity of 1005 mJ/cm²) were 64.49%, 0.88%, 99.7%, and 13.31%, respectively. These results indicate that the hydroxyl radical was produced, under optimum conditions, more in the acidic medium; thus, the RB19 removal efficiency was higher in the acidic medium. The combination of UV rays with oxidants resulted in the production of more hydroxyl radicals and increased removal efficiency.     

烟气中NOx脱除技术的研究进展

综述了干法脱硝、湿法脱硝、微生物法和化学吸收-生物还原法脱除烟气中氮氧化物的原理、技术特点和存在的问题。指出：化学吸收-生物还原法是未来脱除烟气中氮氧化物的主要研究方向之一,可通过提高NO在水中的溶解性,利用微生物去除氮氧化物,力争将其从实验室研究推广至工业应用。     

Development of composites using residue from laminated packaging with discarded foundry sand

Journal of Material Cycles and Waste Management - In recent years, the use of residue for the production of new composite materials has gained prominence as it enables reuse of materials and...     

Phosphate removal from landfill leachate using ferric iron bioremediation under anaerobic condition

Journal of Material Cycles and Waste Management - Landfill leachates contain a variety of contaminants including phosphorus, whose entry into the surface waters should be restricted given the...     

表面活性剂与柠檬酸联合洗涤高黏性土壤中的重金属

以一水合柠檬酸（CA）为洗涤剂,分别采用吐温80（TW80）、十二烷基磺酸钠（SDS）、β-环糊精（BCD）和腐植酸（HA）4种表面活性剂与CA联合洗涤高黏性土壤中的重金属,考察表面活性剂与CA的联合洗脱效果。实验结果表明：添加4种表面活性剂均可提高CA对Cu、Zn和Pb的去除率;处理时无需调节体系pH;在表面活性剂与CA的混合液与土壤的液固比为10:1（mL/g）的条件下,采用一次洗涤即可。经4种表面活性剂与CA联合洗涤后,土壤中Cu、Zn和Pb的离子交换态、碳酸盐结合态和铁锰氧化结合态的占比均下降,而硫化物及有机结合态和残渣态的占比有所提升。     

Study on removal of silver and polyethylene terephthalate from exposed radiography films using enzyme protease

Journal of Material Cycles and Waste Management - In the proposed method, crude enzymes extracted from waste dry leaves of 15 different plants showing protease activity were used for removal of...     

Characterization of polypropylene composites using sludge waste from the natural rubber latex industry as reinforcing filler

Journal of Material Cycles and Waste Management - In the natural rubber latex industries, a huge amount of sludge waste is produced in different processes, which creates potential for use as...     

Simultaneous removal of COD and ammonium from landfill leachate using an anaerobic-aerobic moving-bed biofilm reactor system

The performance of a moving-bed biofilm reactor (MBBR) system with an anaerobic-aerobic arrangement was investigated to treat landfill leachate for simultaneous removal of COD and ammonium. It was found that the anaerobic MBBR played a major role in COD removal due to methanogenesis, and the aerobic MBBR acted as COD-polishing and ammonium removal step. The contribution of the anaerobic MBBR to total COD removal efficiency reached 91% at an organic loading rate (OLR) of 4.08 kgCOD/(m3d), and gradually decreased to 86% when feed OLR was increased to 15.70 kgCOD/(m3d). Because of the complementary function of the aerobic reactor, the total COD removal efficiency of the system had a slight decrease from 94% to 92% even though the feed OLR was increased from 4.08 to 15.70 kgCOD/(m3d). Hydraulic retention time (HRT) had a significant effect on NH+4-N removal; more than 97% of the total NH+4-N removal efficiency could be achieved when the HRT of the aerobic MBBR was more than 1.25 days. The anaerobic-aerobic system had a strong tolerance to shock loading. A decrease in COD removal efficiency of only 7% was observed when the OLR was increased by four times and shock duration was 24 h, and the system could recover the original removal efficiency in 3 days. The average sludge yield of the anaerobic reactor was estimated to be 0.0538 gVSS/gCOD rem.     

Biosorptive removal of Pb(II) and Cu(II) from wastewater using activated carbon from cassava peels

The ability of activated carbon from cassava peels to remove heavy metals like Cu(II) and Pb(II) from hospital wastewater was investigated. The study showed that a pH of 8 was the best for the sorption of both metal ions onto the biosorbent. The time-dependent experiments for the metal ions showed that the binding of the metal ions to the biomass was rapid and occurred within 20–120 min. Sorption efficiency increased with a rise in adsorbent dosage. It increased from 12 to 73 % for Pb(II) and 26 to 79 % for Cu(II) when the adsorbent dose increased from 2 to 12 g. An increase in temperature led to an increase in sorption for both metal ions. The Langmuir model showed that the biomass has a higher sorption capacity for Cu(II) than Pb(II), with q _m = 5.80 mg g^?1 for Pb(II) and 8.00 mg g^?1 for Cu(II). The Freundlich isotherm K _f was 1.4 for Pb(II) and 1.8 for Cu(II), indicating a preferential sorption of Cu(II) onto the biosorbent. Adsorption capacity was found to decrease with an increase in particle sizes. Sorption occurred by physical mechanisms and was mainly controlled by intraparticle diffusion.     

Recovery of iron oxide and calcium chloride from an iron-rich chloride waste using calcium carbonate

Journal of Material Cycles and Waste Management - The ilmenite-chloride process has used for the production of TiCl4 from the ilmenite (FeTiO3) ore, which produces cyclone dust containing mostly...     

Adsorption of Pb2+ and Cd2+ on the l-cysteine-functionalized graphene oxide/chitosan/polyvinyl alcohol hydrogel: Kinetic,isotherm, and thermodynamic study

In this study, polyvinyl alcohol-chitosan-cysteine-functionalized graphene oxide (PCCFG) hydrogel was synthesized from l -cysteine-functionalized graphene oxide (CFG), chitosan (CS), and polyvinyl alcohol (PVA). The hydrogel was characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy and employed for removing lead ion (Pb²⁺) and cadmium ion (Cd²⁺) from aqueous solution. The effects of initial metal ion concentration, hydrogel dose, pH, time, and temperature were studied. The experimental data were well described by a pseudo-second-order kinetic model and Langmuir isotherm with maximum adsorption capacities of 250 and 192 mg g⁻¹ at 25°C for Pb²⁺ and Cd²⁺, respectively. The adsorption capacity of the PCCFG hydrogel increased with an increase in temperature. The value of ∆G° was negative, which shows the spontaneity of the reaction (electron exchange or ion exchange) between the metal ion and electron-rich atoms (–N, –S, –O). The positive ∆H° shows that the adsorption reaction consumes energy and the positive ∆S° shows the strong affinity of PCCFG toward the Pb²⁺ and Cd²⁺ ions. Pb²⁺ had better affinity and less spontaneity than Cd²⁺. The results show that the coexistence of Pb²⁺, Cd²⁺, and Cu²⁺ in the solution inhibits the adsorption capacity of PCCFG.     

TiO2气溶胶快速去除空气中的芥子气模拟剂

在自制反应器内,通过喷射法将纳米TiO_2分散成气溶胶形式,用以降解空气中的芥子气模拟剂二乙基硫醚(DES)。利用自行设计的一套气溶胶沉降行为评价装置,对TiO_2气溶胶的释放条件进行了优化。系统研究了相对湿度、反应温度、光强、催化剂加入量、反应物浓度等因素对DES降解速率和彻底矿化速率的影响。结果表明:TiO_2气溶胶对2.80 mg/L(近似芥子气快速致死浓度)DES降解的半衰期由涂覆型TiO_2的34.5 min缩短至8.5 min;TiO_2气溶胶光催化降解DES的最佳相对湿度为35%,此时CO_2最快生成速率可达34.64μg/(L·min),150 min内彻底矿化比例达66.1%;对于1.5 L反应器,催化剂加入量为30 mg时降解DES的量效比达到最佳状态;TiO_2气溶胶光催化适用于含低浓度DES空气的快速净化。