喷射床电沉积法处理含铜废水的试验研究

以实验室模拟含铜废水为研究对象,采用恒电流喷射床微粒电沉积法对其进行条件试验.结果表明,在pH=3.0、沉积液质量浓度为1 g/L、恒电流为10 A、阴极微粒粒径为1.8 mm、沉积液温度为20℃、鼓入氮气的条件下,铜离子的最大去除率为87.64％,平均电流效率可以达到81.53％,较同等条件下平板电极提高了63％.喷射床微粒电极采用的阴极微粒电极具有较大的比表面积,微粒的喷射循环能够有效地消除沉积过程中出现的浓差极化现象,鼓入氮气可以明显降低沉积液中的溶解氧浓度,从而抑制沉积的金属铜返溶,因此,喷射床微粒电沉积法在处理含铜废水时能够获得较高的电沉积率和电流效率.     

曝气诱导内波破坏水库水温分层的过程与效果

针对传统的水库破坏分层技术的低效率、高能耗等普遍问题,研制了能模拟基于自然对流而形成水温分层的中试模型水库,研究了曝气诱导形成内波混合破坏水温分层的可行性,过程和效果.扬水曝气产生的周期性出流能作为扰动源,在分层水环境中诱导形成内波.内波频率及波幅与曝气量有关.在曝气量0.07~0.28m3/(m2·h),跃温层温度梯度0.29~0.48℃/m的中试条件下,内波破坏分层过程主要以减小表层和底层水温差别、驱使跃温层下潜、等温层变薄为特征,破坏分层的速度与曝气量正相关、与温度梯度负相关.内波通过垂向振荡和横向传播,促进不同温度的水层之间的热交换.相对传统的循环水流混合,在温度梯度约0.32℃/m和0.46℃/m的条件下,当曝气量从0.07m3/(m2·h)逐渐增加到0.28m3/(m2·h)时,内波混合可分别将破坏分层效率提高25.0%~40.0%和41.2%~60.0%.     

Adsorptive removal of basic dyes from aqueous solutions by surfactant modified bentonite clay (organoclay): Kinetic and competitive adsorption isotherm

Cationic surfactant (Hexadecyltrimenthylammonium chloride) modified bentonite clay was prepared and systematically studied for its adsorption behavior as an efficient adsorbent for the removal of basic dyes such as methylene blue (MB), crystal violet (CV) and Rhodamine B (RB) from aqueous phase. Organo modified clay shows better capacity for the removal of three dyes. The adsorption process was found to be dependent on pH and initial dye concentration. The maximum dye sorption was found to be at a pH of 9.0 (99.99% for MB, 95.0% for CV and 83.0% for RB). The adsorption capacity for the dyes was found to be 399.74, 365.11 and 324.36 μmol/g for MB, CV and RB, respectively at 30 °C. The equilibrium uptake was attained within 240 min. The kinetic studies were revealed that sorption follows a pseudo-second-order kinetic model which indicates chemisorption between adsorbent and adsorbate molecules. Adsorption isotherm indicates non-energetically adsorption sites which fit with Freundlich isotherm model. The fitness of kinetics and isotherm models was evaluated by using HYBRID error analysis function. Competitive adsorptions of dyes were studied by using binary component systems.     

旋风除尘器筒体倾斜角的仿真与优化

旋风除尘器结构简单、造价低廉、能耗极低,故得以长期应用,但其除尘效率因设计方法比较粗糙一般在60%以下,从而限制了其使用范围。很多结构参数均影响除尘器的效率,其中除尘器筒体的倾斜角度对效率的影响程度最高。以有限元理论为基础,以Fluent软件为工具,对关于除尘效率与倾斜角度依赖关系进行了系列仿真和优化,得出结论:若空气中颗粒物直径大于2.5μm,除尘器倾斜角为12.4°时,其除尘效率理论上可达到97%以上。通过实验初步验证了上述结果的可信度。     

Hg0 removal from flue gas over different zeolites modified by FeCl3

The elemental mercury removal abilities of three different zeolites(Na A, Na X, HZSM-5)impregnated with iron(Ⅲ) chloride were studied on a lab-scale fixed-bed reactor. X-ray diffraction, nitrogen adsorption porosimetry, Fourier transform infrared spectroscopy,X-ray photoelectron spectroscopy, and temperature programmed desorption(TPD) analyses were used to investigate the physicochemical properties. Results indicated that the pore structure and active chloride species on the surface of the samples are the key factors for physisorption and oxidation of Hg0, respectively. Relatively high surface area and micropore volume are beneficial to efficient mercury adsorption. The active Cl species generated on the surface of the samples were effective oxidants able to convert elemental mercury(Hg0)into oxidized mercury(Hg2+). The crystallization of Na Cl due to the ion exchange effect during the impregnation of Na A and Na X reduced the number of active Cl species on the surface, and restricted the physisorption of Hg0. Therefore, the Hg0 removal efficiencies of the samples were inhibited. The TPD analysis revealed that the species of mercury on the surface of Fe Cl3–HZSM-5 was mainly in the form of mercuric chloride(Hg Cl2), while on Fe Cl3–Na X and Fe Cl3–Na A it was mainly mercuric oxide(Hg O).     

Changes in nitrogen budget and potential risk to the environment over 20 years(1990–2010) in the agroecosystems of the Haihe Basin,China

The nitrogen balance can serve as an indicator of the risk to the environment of nitrogen loss from agricultural land. To investigate the temporal and spatial changes in agricultural nitrogen application and its potential threat to the environment of the Haihe Basin in China, we used a database of county-level agricultural statistics to calculate agricultural nitrogen input, output,surplus intensity, and use efficiency. Chemical fertilizer nitrogen input increased by 51.7% from1990 to 2000 and by 37.2% from 2000 to 2010, concomitant with increasing crop yields.Simultaneously, the nitrogen surplus intensity increased by 53.5% from 1990 to 2000 and by16.5% from 2000 to 2010, presenting a continuously increased environmental risk. Nitrogen use efficiency decreased from 0.46 in 1990 to 0.42 in 2000 and remained constant at 0.42 in 2010,partly due to fertilizer composition and type improvement. This level indicates that more than half of nitrogen inputs are lost in agroecosystems. Our results suggest that although the improvement in fertilizer composition and types has partially offset the decrease in nitrogen use efficiency, the environmental risk has still increased gradually over the past 20 years, along with the increase in crop yields and nitrogen application. It is important to achieve a better nitrogen balance through more effective management to significantly reduce the environmental risk,decrease nitrogen surplus intensity, and increase nitrogen use efficiency without sacrificing crop yields.     

巯基化膨润土对As~(3+)的吸附解吸性能研究

水体及土壤砷污染已引起社会的广泛关注。本研究从7种改性膨润土中筛选出1种对As3+吸附能力较强的材料,即巯基化膨润土。其对As3+的吸附解吸研究显示,吸附在120min后达到平衡;在材料投加量达到0.1 g后,As3+的吸附率基本不变;巯基化膨润土对As3+的吸附受p H、温度及离子强度影响较小,其对As3+的解吸受pH及离子强度影响也较小,且解吸率均小于1%。巯基化材料对As3+的饱和吸附量达到了1.18 mg/g,比钙基膨润土提高了12倍以上;其比表面积比钙基膨润土提高了6倍以上。因此,巯基化膨润土是一种较理想的As 3+吸附材料。     

Hg removal from flue gas over different zeolites modified by FeCl3

The elemental mercury removal abilities of three different zeolites (NaA, NaX, HZSM-5) impregnated with iron(III) chloride were studied on a lab-scale fixed-bed reactor. X-ray diffraction, nitrogen adsorption porosimetry, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and temperature programmed desorption (TPD) analyses were used to investigate the physicochemical properties. Results indicated that the pore structure and active chloride species on the surface of the samples are the key factors for physisorption and oxidation of Hg⁰, respectively. Relatively high surface area and micropore volume are beneficial to efficient mercury adsorption. The active Cl species generated on the surface of the samples were effective oxidants able to convert elemental mercury (Hg⁰) into oxidized mercury (Hg^2 +). The crystallization of NaCl due to the ion exchange effect during the impregnation of NaA and NaX reduced the number of active Cl species on the surface, and restricted the physisorption of Hg⁰. Therefore, the Hg⁰ removal efficiencies of the samples were inhibited. The TPD analysis revealed that the species of mercury on the surface of FeCl₃–HZSM-5 was mainly in the form of mercuric chloride (HgCl₂), while on FeCl₃–NaX and FeCl₃–NaA it was mainly mercuric oxide (HgO).     

Preparation and evaluation of aminopropyl-functionalized manganese-loaded SBA-15 for copper removal from aqueous solution

A novel material, aminopropyl-functionalized manganese-loaded SBA-15 (NH₂-Mn-SBA-15), was synthesized by bonding 3-aminopropyl trimethoxysilane (APTMS) onto manganese-loaded SBA-15 (Mn-SBA-15) and used as a Cu^2 + adsorbent in aqueous solution. Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction spectra (XRD), N₂ adsorption/desorption isotherms, high resolution field emission scanning electron microscopy (FESEM) and X-ray photoelectron spectroscopy (XPS) were used to characterize the NH₂-Mn-SBA-15. The ordered mesoporous structure of SBA-15 was remained after modification. The manganese oxides were mainly loaded on the internal surface of the pore channels while the aminopropyl groups were mainly anchored on the external surface of SBA-15. The adsorption of Cu^2 + on NH₂-Mn-SBA-15 was fitted well by the Langmuir equation and the maximum adsorption capacity of NH₂-Mn-SBA-15 for Cu^2 + was over two times higher than that of Mn-SBA-15 under the same conditions. The Elovich equation gave a good fit for the adsorption process of Cu^2 + by NH₂-Mn-SBA-15 and Mn-SBA-15. Both the loaded manganese oxides and the anchored aminopropyl groups were found to contribute to the uptake of Cu^2 +. The NH₂-Mn-SBA-15 showed high selectivity for copper ions. Consecutive adsorption–desorption experiments showed that the NH₂-Mn-SBA-15 could be regenerated by acid treatment without altering its properties.