Enhanced carbon tetrachloride degradation by hydroxylamine in ferrous ion activated calcium peroxide in the presence of formic acid

• Complete CT degradation was achieved by employing HA to CP/Fe(II)/FA process. • Quantitative detection of Fe(II) regeneration and HO• production was investigated. • Benzoic acid outcompeted FA for the reaction with HO•. • CO₂•⁻ was the dominant reductive radical for CT removal. • Effects of solution matrix on CT removal were conducted. Hydroxyl radicals (HO•) show low reactivity with perchlorinated hydrocarbons, such as carbon tetrachloride (CT), in conventional Fenton reactions, therefore, the generation of reductive radicals has attracted increasing attention. This study investigated the enhancement of CT degradation by the synergistic effects of hydroxylamine (HA) and formic acid (FA) (initial [CT] = 0.13 mmol/L) in a Fe(II) activated calcium peroxide (CP) Fenton process. CT degradation increased from 56.6% to 99.9% with the addition of 0.78 mmol/L HA to the CP/Fe(II)/FA/CT process in a molar ratio of 12/6/12/1. The results also showed that the presence of HA enhanced the regeneration of Fe(II) from Fe(III), and the production of HO• increased one-fold when employing benzoic acid as the HO• probe. Additionally, FA slightly improves the production of HO•. A study of the mechanism confirmed that the carbon dioxide radical (CO₂•⁻), a strong reductant generated by the reaction between FA and HO•, was the dominant radical responsible for CT degradation. Almost complete CT dechlorination was achieved in the process. The presence of humic acid and chloride ion slightly decreased CT removal, while high doses of bicarbonate and high pH inhibited CT degradation. This study helps us to better understand the synergistic roles of FA and HA for HO• and CO₂•⁻ generation and the removal of perchlorinated hydrocarbons in modified Fenton systems.     

球磨零价镁/石墨(ZVMg/C)降解水中三氯乙烯

利用机械球磨法制备了零价镁/石墨(ZVMg/C)材料,并将其用于水溶液中三氯乙烯(TCE)的降解.研究通过SEM、BET和XRD等分析手段解析了ZVMg/C的表面形态结构和成分组成;采用正交实验方法优化了ZVMg/C的制备参数,比较了石墨含量对材料性能的影响;并考察了ZVMg/C投加量、溶液初始pH和地下水中常见阴(C...     

Effect of current density on groundwater arsenite removal performance using air cathode electrocoagulation

• With the same charge, current density had little effect on As(III) removal in ACEC. • ACEC had the lowest energy consumption compared with EC/O₂ or EC/N₂. • There was a trade-off relationship between energy consumption and removal time. • The ·OH concentration in ACEC was 1.5 times of that in the EC/O₂ system. Naturally occurring arsenic enrichment in groundwater poses a huge threat to human health. Air cathode electrocoagulation (ACEC) has recently been proposed to enhance As(III) oxidation and lower energy consumption. In this study, ACEC, EC/O₂ and EC/N₂ were evaluated with different current densities from 1 to 8 mA/cm² to investigate the effect on As(III) removal in different redox environments. Current density had no appreciable effect on arsenic removal efficiency given the same charge in ACEC because the concentration ratio of Fe/H₂O₂ under different current densities remained stable. However, in EC/O₂ and EC/N₂, As(III) removal was inhibited at higher current densities (4–8 mA/cm²), likely because more Fe(II) competed with As(III) for the oxidant, leading to less effective oxidation of As(III). In all EC systems, the ·OH units generated per power consumption reached the highest value at the lowest current density. Compared with other EC systems, the ACEC system showed lower energy consumption at all current densities due to the low energy consumption of the electrode reaction and more free radical generation. A lower current density saved more energy at the expense of time, showing the trade-off relationship between energy consumption and removal time. The operation costs for As(III) removal under optimal conditions were calculated as 0.028 $/m³ for ACEC, 0.030 $/m³ for EC/O₂, and 0.085 $/m³ for EC/N₂     

Enhanced triallyl isocyanurate (TAIC) degradation through application of an O3/UV process: Performance optimization and degradation pathways

• UV/O₃ process had higher TAIC mineralization rate than O₃ process. • Four possible degradation pathways were proposed during TAIC degradation. • pH impacted oxidation processes with pH of 9 achieving maximum efficiency. • CO₃^2– negatively impacted TAIC degradation while HCO₃^– not. • Cl^– can be radicals scavenger only at high concentration (over 500 mg/L Cl^–). Triallyl isocyanurate (TAIC, C₁₂H₁₅N₃O₃) has featured in wastewater treatment as a refractory organic compound due to the significant production capability and negative environmental impact. TAIC degradation was enhanced when an ozone(O₃)/ultraviolet(UV) process was applied compared with the application of an independent O₃ process. Although 99% of TAIC could be degraded in 5 min during both processes, the O₃/UV process had a 70%mineralization rate that was much higher than that of the independent O₃ process (9%) in 30 min. Four possible degradation pathways were proposed based on the organic compounds of intermediate products identified during TAIC degradation through the application of independent O₃ and O₃/UV processes. pH impacted both the direct and indirect oxidation processes. Acidic and alkaline conditions preferred direct and indirect reactions respectively, with a pH of 9 achieving maximum Total Organic Carbon (TOC) removal. Both CO₃^2– and HCO₃^– decreased TOC removal, however only CO₃^2– negatively impacted TAIC degradation. Effects of Cl^– as a radical scavenger became more marked only at high concentrations (over 500 mg/L Cl^–). Particulate and suspended matter could hinder the transmission of ultraviolet light and reduce the production of HO· accordingly.     

Enhanced reductive degradation of carbon tetrachloride by carbon dioxide radical anion-based sodium percarbonate/Fe(II)/formic acid system in aqueous solution

Complete CT degradation was achieved by SPC/Fe(II)/FA system.Formic acid established the reductive circumstance by producing CO₂·^–.CO₂·^– was the dominant active species responsible for CT degradation.CT degradation was favorable in the pH range from 3.0 to 9.0.SPC/Fe(II)/FA system may be suitable for CT remediation in contaminated groundwater.The performance of sodium percarbonate (SPC) activated with ferrous ion (Fe(II)) with the addition of formic acid (FA) to stimulate the degradation of carbon tetrachloride (CT) was investigated. Results showed that CT could be entirely reduced within 15 min in the system at a variety of SPC/Fe(II)/FA/CT molar ratios in experimental level. Scavenging tests indicated that carbon dioxide radical anion (CO2·^–) was the dominant reactive oxygen species responsible for CT degradation. CT degradation rate, to a large extent, increased with increasing dosages of chemical agents and the optimal molar ratio of SPC/Fe(II)/FA/CT was set as 60/60/60/1. The initial concentration of CT can hardly affect the CT removal, while CT degradation was favorable in the pH range of 3.0–9.0, but apparently inhibited at pH 12. Cl^– and HCO₃^– of high concentration showed negative impact on CT removal. Cl^– released from CT was detected and the results confirmed nearly complete mineralization of CT. CT degradation was proposed by reductive C-Cl bond splitting. This study demonstrated that SPC activated with Fe(II) with the addition of FA may be promising technique for CT remediation in contaminated groundwater.     

Remediation of 2,4-dichlorophenol-contaminated groundwater using nano-sized CaO2 in a two-dimensional scale tank

• Nano CaO₂ is evaluated as a remediation agent for 2,4-DCP contaminated groundwater. • 2,4-DCP degradation mechanism by different Fe²⁺ concentration was proposed. • 2,4-DCP was not degraded in the system for solution pH>10. • The 2,4-DCP degradation area is inconsistent with the nano CaO₂ distribution area. This study evaluates the applicability of nano-sized calcium peroxide (CaO₂) as a source of H₂O₂ to remediate 2,4-dichlorophenol (2,4-DCP) contaminated groundwater via the advanced oxidation process (AOP). First, the effect and mechanism of 2,4-DCP degradation by CaO₂ at different Fe concentrations were studied (Fenton reaction). We found that at high Fe concentrations, 2,4-DCP almost completely degrades via primarily the oxidation of •OH within 5 h. At low Fe concentrations, the degradation rate of 2,4-DCP decreased rapidly. The main mechanism was the combined action of •OH and O₂^•−. Without Fe, the 2,4-DCP degradation reached 13.6% in 213 h, primarily via the heterogeneous reaction on the surface of CaO₂. Besides, 2,4-DCP degradation was significantly affected by solution pH. When the solution pH was>10, the degradation was almost completely inhibited. Thus, we adopted a two-dimensional water tank experiment to study the remediation efficiency CaO₂ on the water sample. We noticed that the degradation took place mainly in regions of pH<10 (i.e., CaO₂ distribution area), both upstream and downstream of the tank. After 28 days of treatment, the average 2,4-DCP degradation level was ≈36.5%. Given the inadequacy of the results, we recommend that groundwater remediation using nano CaO₂: (1) a buffer solution should be added to retard the rapid increase in pH, and (2) the nano CaO₂ should be injected copiously in batches to reduce CaO₂ deposition.     

Comparison of different valent iron on anaerobic sludge digestion: Focusing on oxidation reduction potential,dissolved organic nitrogen and microbial community

• ORP value from −278.71 to −379.80 mV showed indiscernible effects on methane yield. • Fe(II) and Fe(III) promoted more degradation of proteins and amino acids than Fe⁰. • The highest enrichment of Geobacter was noted in samples added with Fe⁰. • Cysteine was accumulated during iron enhanced anaerobic sludge digestion. • Both iron content and valence were important for methane production. This study compared effects of three different valent iron (Fe⁰, Fe(II) and Fe(III)) on enhanced anaerobic sludge digestion, focusing on the changes of oxidation reduction potential (ORP), dissolved organic nitrogen (DON), and microbial community. Under the same iron dose in range of 0−160 mg/L after an incubation period of 30 days (d), the maximum methane production rate of sludge samples dosed with respective Fe⁰, Fe(II) and Fe(III) at the same concentration showed indiscernible differences at each iron dose, regardless of the different iron valence. Moreover, their behavior in changes of ORP, DON and microbial community was different: (1) the addition of Fe⁰ made the ORP of sludge more negative, and the addition of Fe(II) and Fe(III) made the ORP of sludge less negative. However, whether being more or less negative, the changes of ORP may show unobservable effects on methane yield when it ranged from −278.71 to −379.80 mV; (2) the degradation of dissolved organic nitrogen, particularly proteins, was less efficient in sludge samples dosed with Fe⁰ compared with those dosed with Fe(II) and Fe(III) after an incubation period of 30 d. At the same dose of 160 mg/L iron, more cysteine was noted in sludge samples dosed with Fe(II) (30.74 mg/L) and Fe(III) (27.92 mg/L) compared with that dosed with Fe⁰ (21.75 mg/L); (3) Fe⁰ particularly promoted the enrichment of Geobacter, and it was 6 times higher than those in sludge samples dosed with Fe(II) and Fe(III) at the same dose of 160 mg/L iron.     

2019年秋季三亚市一次典型臭氧污染个例气象成因解析

三亚市位于海南岛最南端,旅游资源丰富,生态环境良好,是海南建设国际旅游岛和国家生态文明试验区的重要城市之一。2019年秋季三亚市出现的一次臭氧(Ozone,O₃)污染过程,为科学认识三亚市此次O₃污染特征及气象学成因,也为进一步开展O₃污染预警预报和科学治理提供技术支撑,利用2019年11月1—6日三亚市生态环境局对外发布的大气污染物数据,以及地面常规观测数据,结合ECMWF发布的第5代资料(the fifth generation ECMWF reanalysis data,ERA5),采用相关分析和后向轨迹模型对其进行分析。结果表明,11月4日和5日O₃-8 h(臭氧最大8 h滑动平均)分别为162μg·m^-3和180μg·m^-3,超标百分比为101.25%和112.50%。5日O₃-1 h(臭氧最大1 h平均)达到了203μg·m^-3,超标百分比为101.50%。14:00—19:00是O₃     

Oxidation and biotoxicity assessment of microcystin-LR using different AOPs based on UV,O3 and H2O2

MC-LR removal performances under different AOPs were compared systematically. Higher removal efficiency and synergistic effects were obtained by combined process. The acute biotoxicity raised in different degrees after oxidation. Microcystin-LR attracts attention due to its high toxicity, high concentration and high frequency. The removal characteristics of UV/H₂O₂ and O₃/H₂O₂ advanced oxidation processes and their individual process for MC-LR were investigated and compared in this study. Both the removal efficiencies and rates of MC-LR as well as the biotoxicity of degradation products was analyzed. Results showed that the UV/H₂O₂ process and O₃/H₂O₂ were effective methods to remove MC-LR from water, and they two performed better than UV-, O₃-, H₂O₂-alone processes under the same conditions. The effects of UV intensity, H₂O₂ concentration and O₃ concentration on the removal performance were explored. The synergistic effects between UV and H₂O₂, O₃ and H₂O₂ were observed. UV dosage of 1800 mJ·cm⁻² was required to remove 90% of 100 mg·L⁻¹ MC-LR, which amount significantly decreased to 500 mJ·cm⁻² when 1.7 mg·L⁻¹ H₂O₂ was added. 0.25 mg·L⁻¹ O₃, or 0.125 mg·L⁻¹ O₃ with 1.7 mg·L⁻¹ H₂O₂ was needed to reach 90% removal efficiency. Furthermore, the biotoxicity results about these UV/H₂O₂, O₃/H₂O₂ and O₃-alone processes all present rising trends with oxidation degree of MC-LR. Biotoxicity of solution, equivalent to 0.01 mg·L⁻¹ Zn²⁺, raised to 0.05 mg·L⁻¹ Zn²⁺ after UV/H₂O₂ or O₃/H₂O₂ reaction. This phenomenon may be attributed to the aldehydes and ketones with small molecular weight generated during reaction. Advice about the selection of MC-LR removal methods in real cases was provided.     

乌鲁木齐市米东区大气降水的化学特征及来源分析

为研究乌鲁木齐市米东区大气降水中的化学组分特征及来源,对2017-2019年降水中主要离子浓度及来源进行了分析.研究结果显示,米东区2017-2019年降水的雨量加权pH年均值为7.95,雨量加权平均电导率年均值为16.15 mS·m-1,雨量加权平均总离子浓度为72.75-95.89 μeq·L-1,年均浓度为81....     

Denitrification potential in a Louisiana wetland receiving diverted Mississippi River water

Excess nitrate in Mississippi River water entering offshore areas is reported to contribute to low oxygen (hypoxia) conditions in the Gulf of Mexico. Excessive algal growth driven by the excess nitrogen results in a decrease in dissolved oxygen in bottom water. Reintroduction of Mississippi River waters into a Louisiana coastal wetland has the potential to reduce the amount of nitrate reaching offshore waters. In this study, reduction in the concentration of added NO₃^- was determined in sediment-water-columns collected from a wetland site in Breton Sound estuary receiving nutrient inputs from the Mississippi River. The capacity of a wetland to process nitrate in floodwater was determined in the laboratory. The rates of NO₃^- removal (determined from change in nitrate concentration in the floodwater) averaged 97 mg N m^-2 d^-1 over 16 d for a 1750-mg NO₃-N m^-2 addition, and 170 mg N m^-2 d^-1 over 16 d for a 3500-mg NO₃-N m^-2 addition. The total N₂O-N emissions from the 1750- and 3500-mg NO₃-N m^-2 additions were 19 and 54 mg N m^-2 accounting for 1.1% and 1.5% of the applied NO₃-N, respectively. Using the acetylene-inhibition technique, the average denitrification rate was determined to be 57 and 87 mg N m^-2 d^-1 (21 and 32 g N m^-2 yr^-1) during the most active denitrification period of 5 d after incubation for 1750 and 3500 mg NO₃^--N m^-2 of added nitrate in floodwater, respectively. The total N evolved over 11 d as N₂O + N₂ was equivalent to 436 and 921 mg N m^-2 (24.9% and 26.3%, respectively, of added N). Increasing the amount of NO₃^- applied to the overlying water increased the rate of NO₃^- loss and N₂O emission significantly. The thickness of the oxidized surface sediment layer was also influenced by the NO₃^- application to the floodwater with a significant linear correlation between nitrate addition and thickness of the oxidized layer (r = 0.9998, p = 0.01). This study indicates that wetlands receiving diverted Mississippi River water have the potential to process and remove NO₃^- in the river water, reducing the amount of NO₃^- reaching to offshore areas.     

Species distribution of arsenic in sediments after an unexpected emergent discharge of high-arsenic wastewater into a river

The unexpected emergent discharge of high-arsenic wastewater into water environments results in significantly increased levels of arsenic in water; however, the species distribution of arsenic in sediments has never been reported before for such cases. This study focuses on an As pollution accident in the Dasha River, and uses sequential extraction procedures with deionized water, 1?mol·L^-1 MgCl₂ at pH= 8, 1?mol·L^-1 NaH₂PO₄ at pH= 5, and 1?mol·L^-1 HCl to investigate four binding phases of arsenic (i.e., water soluble, ion-exchangeable, strongly-bound, and precipitates) in sediments at different layers in different cross-sections along the river. The average ratio of arsenite (As(III)) to arsenate (As(V)) was found to decrease from 0.74:1 in river water to 0.48:1 in sediment, owing to its higher affinity toward As(V) than As(III). The content of arsenic in the sediments was relatively low and the maximum content was observed to be 36.3?mg·kg^-1 for As(III) and 97.5?mg·kg^-1 for As(V). As(III) and As(V) showed different binding phases in sediments, and the average fractions of these four species were determined to be 0.09, 0.11, 0.17, and 0.63 for As(III) and 0.03, 0.14, 0.63, and 0.20 for As(V), respectively. For all the sediment samples, the content of arsenic showed no relationship with the characteristics of the sediments such as the particle diameter, the content of organic carbon, Fe, and Mn, although a negative correlation with particle diameter was observed for the sediments in the uppermost 2-cm layer. The unexpected emergent As incident results in the high content of total arsenic in the surface sediment, which may be potential secondary source to the elevated As levels in surface water.     

Ozone kinetics of dimethyl sulfide in the presence of water vapor

The outdoor smog chamber was used to thorough investigate the rate constants of gas-phase reaction between dimethyl sulfide （DMS） and ozone （O3） under conditions of relative humidity 55.0%-67.8% at （296±2）K for the first time. The rate constants were measured, at a total pressure of 1 atm, to be （10.4±0.2） × 10^-19 cm^3·molecule^-1·s^-1 at relative humidity of 67.5%±0.3% at 298K, （10.1±0.1） × 10^-19cm^3·molecule^-1·s^-1 at relative humidity of 66.5%±0.5% at 296K, （7.75±0.39） × 10^-19cm^3·molecule^-1·s^-1 at relative humidity of 64.8%± 0.1% at 294K and （3.42±0.21） × 10^-19cm^3·molecu- le^-1·s^-1at relative humidity of 55.8%±0.8% at 295K. Base on these results, it is possible to see the reaction of O3/ DMS in the presence of water vapor as an important sink for DMS in the earth atmosphere.     

Effect of metal ion-doping on characteristics and photocatalytic activity of TiO2 nanotubes for removal of humic acid from water

The effect of ion-doping on TiO₂ nanotubes were investigated to obtain the optimal TiO₂ nanotubes for the effective decomposition of humic acids (HA) through O₃/UV/ion-doped TiO₂ process. The experimental results show that changing the calcination temperature, which changed the weight fractions of the anatase phase, the average crystallite sizes, the Brunauer-Emmett-Teller surface area, and the energy band gap of the catalyst, affected the photocatalytic activity of the catalyst. The ionic radius, valence state, and configuration of the dopant also affected the photocatalytic activity. The photocatalytic activities of the catalysts on HA removal increased when Ag⁺, Al³⁺, Cu²⁺, Fe³⁺, V⁵⁺, and Zn²⁺ were doped into the TiO₂ nanotubes, whereas such activities decreased as a result of Mn²⁺- and Ni²⁺-doping. In the presence of 1.0 at.% Fe³⁺-doped TiO₂ nanotubes calcined at 550°C, the removal efficiency of HA was 80% with a pseudo-first-order rate constant of 0.158 min⁻¹. Fe³⁺ in TiO₂ could increase the generation of ·OH, which could remove HA. However, Fe³⁺ in water cannot function as a shallow trapping site for electrons or holes.     

Redox reactions of iron and manganese oxides in complex systems

• Mechanisms of redox reactions of Fe- and Mn-oxides were discussed. • Oxidative reactions of Mn- and Fe-oxides in complex systems were reviewed. • Reductive reaction of Fe(II)/iron oxides in complex systems was examined. • Future research on examining the redox reactivity in complex systems was suggested. Conspectus Redox reactions of Fe- and Mn-oxides play important roles in the fate and transformation of many contaminants in natural environments. Due to experimental and analytical challenges associated with complex environments, there has been a limited understanding of the reaction kinetics and mechanisms in actual environmental systems, and most of the studies so far have only focused on simple model systems. To bridge the gap between simple model systems and complex environmental systems, it is necessary to increase the complexity of model systems and examine both the involved interaction mechanisms and how the interactions affected contaminant transformation. In this Account, we primarily focused on (1) the oxidative reactivity of Mn- and Fe-oxides and (2) the reductive reactivity of Fe(II)/iron oxides in complex model systems toward contaminant degradation. The effects of common metal ions such as Mn²⁺ , Ca²⁺, Ni²⁺, Cr³⁺ and Cu²⁺, ligands such as small anionic ligands and natural organic matter (NOM), and second metal oxides such as Al, Si and Ti oxides on the redox reactivity of the systems are briefly summarized.     

辽宁西南典型城市冬季大气细颗粒物水溶性无机离子污染特征及来源解析

本研究于2018年12月3日-2019年1月1日在辽宁省西南典型城市葫芦岛市和朝阳市分别布设3个城区采样点,在区域传输点龙屯水库布设1个采样点,采集大气细颗粒物PM2.5样品(n=201).使用离子色谱检测样品中的Na+、Mg2+、Ca2+、K+、NH4+、SO42-、F-、Cl-和NO3-的质量浓度.观测期间PM2....     

Utilization of nano/micro-size iron recovered from the fine fraction of automobile shredder residue for phenol degradation in water

Phenol removal by n/m Fe in the presence of H₂O₂ was highly effective. Increasing the amounts of n/m Fe and H₂O₂?increased the phenol removal rate. Phenol removal was decreased with an increase in the concentration of phenol. The natural pH (6.9) of the solution was highly effective for phenol removal. The pseudo-first-order kinetics was best fitted for the degradation of phenol. The study investigates the magnetic separation of Fe from automobile shredder residue (ASR) (<0.25 mm) and its application for phenol degradation in water. The magnetically separated Fe was subjected to an ultrasonically assisted acid treatment, and the degradation of phenol in an aqueous solution using nano/micro-size Fe (n/m Fe) was investigated in an effort to evaluate the possibility of utilizing n/m Fe to remove phenol from wastewater. The prepared n/m Fe was analyzed by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The effects of the dosages of n/mFe, pH, concentration of phenol and amount of H₂O₂ on phenol removal were evaluated. The results confirm that the phenol degradation rate was improved with an increase in the dosages of n/mFe and H₂O₂; however, the rate is reduced when the phenol concentration is higher. The degradation of phenol by n/mFe followed the pseudo-first-order kinetics. The value of the reaction rate constant (k) was increased as the amounts of n/m Fe and H₂O₂ increased. Conversely, the value of k was reduced when the concentration of phenol was increased. The probable mechanism behind the degradation of phenol by n/m Fe is the oxidation of phenol through hydroxyl radicals which are produced during the reaction between H₂O₂ and n/m Fe.     

铁基生物炭钝化Cd大田试验研究

近年来,稻田Cd污染引起的环境及健康问题日益突出。应用钝化技术对土壤中有效性Cd进行钝化对稻田生态系统中Cd的生物地球化学循环具有重要的理论和实际意义。在广东省韶关市仁化县董塘镇红星村一受Cd污染的稻田上,设置大田试验,研究铁基生物炭对Cd在大田土壤-水稻系统迁移的影响以及对作物产量的影响。试验共设6个处理:(1)空白对照;(2)每一季水稻插秧前,一次性施加1500 kg·hm^-2的普通生物炭;(3)每一季水稻插秧前,一次性施加75 kg·hm^-2的零价铁(Fe0);(4)每一季水稻插秧前,一次性施加1500 kg·hm^-2、ω(Fe)=1%的铁基生物炭(ω(Fe)=1%in Fe-Biochar);(5)每一季水稻插秧前,一次性施加1500 kg·hm^-2、ω(Fe)=3%的铁基生物炭(ω(Fe)=3%in Fe-Biochar);(6)每一季水稻插秧前,一次性施加1500 kg·hm^-2、ω(Fe)=5%的铁基生物炭(ω(Fe)=5%in Fe-Biochar)。结果表明:(1)施用生物炭、铁粉和铁基生物炭土壤钝化调理剂可以增加水稻产量,显著降低籽粒重金属Cd含量;(2)施用铁基生物炭可以显著增加水稻根表铁膜Fe含量,同时显著增加水稻根表铁膜固定的Cd量,抑制重金属Cd向籽粒的运输累积。综合考虑施用成本和钝化效果,对于Cd污染稻田,建议施用1500 kg·hm^-2、ω(Fe)=3%的铁基生物炭材料。     

Catalytic hydrolysis of gaseous HCN over Cu–Ni/γ-Al2O3 catalyst: parameters and conditions

? The Cu–Ni/γ-Al₂O₃ catalyst was prepared to study HCN hydrolysis ? On catalyst calcined at 400°C, the HCN removal efficiency reaches a maximum. ? HCN removal is the highest at 480 min at a H ₂ O/HCN volume ratio of 150 ? The presence of CO facilitates HCN hydrolysis and increases NH ₃ production. ? O ₂ increases the HCN removal and NO_x production but decreases NH ₃ production GRAPHIC ABSTRACT To decompose efficiently hydrogen cyanide (HCN) in exhaust gas, g-Al₂O₃-supported bimetallic-based Cu–Ni catalyst was prepared by incipient-wetness impregnation method. The effects of the calcination temperature, H₂O/HCN volume ratio, reaction temperature, and the presence of CO or O₂ on the HCN removal efficiency on the Cu–Ni/g-Al₂O₃ catalyst were investigated. To examine further the efficiency of HCN hydrolysis, degradation products were analyzed. The results indicate that the HCN removal efficiency increases and then decreases with increasing calcination temperature and H₂O/HCN volume ratio. On catalyst calcined at 400°C, the efficiency reaches a maximum close to 99% at 480 min at a H₂O/HCN volume ratio of 150. The HCN removal efficiency increases with increasing reaction temperature within the range of 100°C–500°C and reaches a maximum at 500°C. This trend may be attributed to the endothermicity of HCN hydrolysis; increasing the temperature favors HCN hydrolysis. However, the removal efficiencies increases very few at 500°C compared with that at 400°C. To conserve energy in industrial operations, 400°C is deemed as the optimal reaction temperature. The presence of CO facilitates HCN hydrolysis andincreases NH₃ production. O₂ substantially increases the HCN removal efficiency and NO_x production but decreases NH₃ production.     

Fe2O3-CeO2-Bi2O3/γ-Al2O3 catalyst in the catalytic wet air oxidation (CWAO) of cationic red GTL under mild reaction conditions

Fe₂O₃-CeO₂-Bi₂O₃/γ-Al₂O₃, an environmental friendly material, was investigated. The catalyst exhibited good catalytic performance in the CWAO of cationic red GTL. The apparent activation energy for the reaction was 79 kJ·mol⁻¹. HO₂· and O₂·⁻ appeared as the main reactive species in the reaction. The Fe₂O₃-CeO₂-Bi₂O₃/γ-Al₂O₃ catalyst, a novel environmental-friendly material, was used to investigate the catalytic wet air oxidation (CWAO) of cationic red GTL under mild operating conditions in a batch reactor. The catalyst was prepared by wet impregnation, and characterized by special surface area (BET measurement), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The Fe₂O₃-CeO₂-Bi₂O₃/γ-Al₂O₃ catalyst exhibited good catalytic activity and stability in the CWAO under atmosphere pressure. The effect of the reaction conditions (catalyst loading, degradation temperature, solution concentration and initial solution pH value) was studied. The result showed that the decolorization efficiency of cationic red GTL was improved with increasing the initial solution pH value and the degradation temperature. The apparent activation energy for the reaction was 79 kJ·mol⁻¹. Hydroperoxy radicals (HO₂·) and superoxide radicals (O₂⁻·) appeared as the main reactive species upon the CWAO of cationic red GTL.