Numerical modeling and performance evaluation of passive convergence-permeable reactive barrier (PC-PRB)

● A 2D finite-element solute transport model, PRB-Trans, is developed. ● PC-PRB can significantly improve the remediation efficiency of PRB. ● PC-PRB can considerably reduce the required PRB dimensions and materials costs. ● The required PRB length decreases with the increase of pipe length, L _p. The passive convergence-permeable reactive barrier (PC-PRB) was proposed to address the limitations of traditional PRB configurations. To evaluate the hydraulic and pollutant removal performance of the PC-PRB system, we developed a simulation code named PRB-Trans. This code uses the two-dimensional (2D) finite element method to simulate groundwater flow and solute transport. Case studies demonstrate that PC-PRB technology is more efficient and cost-effective than continuous permeable reactive barrier (C-PRB) in treating the same contaminated plume. Implementation of PC-PRB technology results in a 33.3% and 72.7% reduction in PRB length (L_PRB) and height (H_PRB), respectively, while increasing 2D horizontal and 2D vertical pollutant treatment efficiencies of PRB by 87.8% and 266.8%, respectively. In addition, the PC-PRB technology has the ability to homogenize the pollutant concentration and pollutant flux through the PRB system, which can mitigate the problems arising from uneven distribution of pollutants in the C-PRB to some extent. The L_PRB required for PC-PRB decreases as the water pipe length (L_p) increases, while the H_PRB required initially decreases and then increases with increasing L_p. The effect of passive well height (H_w) on H_PRB is not as significant as that of L_p on H_PRB. Overall, PC-PRB presents a promising and advantageous PRB configuration in the effective treatment of various types of contaminated plumes.     

异质性企业环境责任与碳绩效的关系研究：媒体关注和环境规制的联合调节效应

“双碳”愿景下微观企业层面的环境责任受到更多关注。本文运用Python获取2014—2019年中国A股上市工业企业数据,分析了异质性企业环境责任对碳绩效的影响,探讨了媒体关注和环境规制在其中的联合调节效应。研究表明：履行前瞻型环境责任和反应型环境责任均对企业碳绩效有显著的增进作用;媒体关注可以正向调节前瞻型企业环境责任和碳绩效的关系,但在反应型企业环境责任与碳绩效间的调节作用不显著。进一步研究发现：环境规制与媒体关注在反应型企业环境责任和碳绩效间产生正向联合调节作用,而在前瞻型环境责任与碳绩效间的联合调节作用不显著。研究结果支持了政府和媒体对企业环境责任的正式和非正式治理效果,进而提高了企业碳绩效的作用逻辑,拓展了对企业碳绩效影响因素以及异质性企业环境责任的理论研究,将环境治理他治和自治相结合,为多元环境治理主体协同联动推进“双碳”目标顺利实现提供新思路和参考证据。     

Regenerable adsorbent for removing ammonia evolved from anaerobic reaction of animal urine

The waste gas evolved from biodegradation of animal urine contains ammonia causing environmental concerns. A new and effective method for removing ammonia from such waste gas using reactive adsorption is presented. In the process, activated carbon impregnated with H2SO4（H2SO4/C） is employed. Ammonia in the waste gas reacts with H2SO4 on the adsorbent instantaneously and completely to form （NIL）2SO4. The H2SO4/C adsorbent is high in NH3 adsorption capacity and regenerable. The NH3 removal capacity of this regenerable adsorbent is more than 30 times that of the adsorbents used normally in the industry. The spent H2SO4/C is regenerated by flowing low-pressure steam through the adsorbent bed to remove the （NH4）2SO4 from the adsorbent. The regeneration by-product is concentrated （NH4）2SO4 solution, which is a perfect liquid fertilizer for local use. Re-soaking the activated carbon with H2SO4 solution rejuvenates the activity of the adsorbent. Thus the H2SOJC can be reused repeatedly. In the mechanism of this reactive adsorption process, trace of H20 in the waste gas is a required, which lends itself to treating ammonia gas saturated with moisture from biodegradation of animal urine.     

铁屑法处理活性艳红废水动力学模型

研究了铁屑法处理性艳红染料（Ｋ－２ＢＰ）废水的脱色过程和铁屑溶解过程动力学模型。脱色反应为一级反应，铁屑溶解符合零级反应。了固－液比，温度、ＰＨ、铁屑粒径、活化时间等诸因素对反庆速度常数的影响。     

Model-based evaluation of controlled-release systems in the remediation of dissolved plumes in groundwater

Controlled-release, semi-passive reactive barrier systems have been recently developed as a long-term treatment option for controlling the spread of contaminant plumes in groundwater. This paper describes a new computer code, and applies it to study coupled processes of solute release, reaction, and mass transport in an in situ remediation scheme using the controlled release of potassium permanganate. Confidence with the modeling approach was developed by model verifications and simulating results of a pilot-scale test-cell experiment. Sensitivity analyses indicated the possibilities of treatment inefficiencies due to inability of transverse dispersion to mix the permanganate (MnO(4)(-)) within the zone of reaction, fluctuations in source strength due to variations in flow velocity, and the small length of treatment zone due to strong soil utilization of MnO(4)(-). Although problems associated with the fluctuating source strength and strong soil utilization can be addressed by optimizing the release rate, the inefficiency of transverse dispersion to create mixing could pose a serious limitation. Through a series of model simulations, a system of injection/withdrawal wells in a doublet arrangement was developed to facilitate lateral spreading and mixing of MnO(4)(-). A well-mixed, stable MnO(4)(-) zone with predetermined size (DxL=8m x 2m) and concentration ranges (1.5-20 mg l(-1)) was created by four 1-day injection/withdrawal pumping periods over 24 d. This type of mixing zone may persist for many years with periodic well mixing and replacements of exhausted controlled-release forms. Coupled use of the generalized code with field hydrologic data will help to optimize the design and operation of controlled-release systems in practice.     

A calcite permeable reactive barrier for the remediation of Fluoride from spent potliner (SPL) contaminated groundwater

The use of calcite (CaCO3) as a substrate for a permeable reactive barrier (PRB) for removing fluoride from contaminated groundwater is proposed and is illustrated by application to groundwater contaminated by spent potliner leachate (SPL), a waste derived from the aluminium smelting process. The paper focuses on two issues in the implementation of calcite permeable reactive barriers for remediating fluoride contaminated water: the impact of the groundwater chemical matrix and CO2 addition on fluoride removal. Column tests comparing pure NaF solutions, synthetic SPL solutions, and actual SPL leachate indicate that the complex chemical matrix of the SPL leachate can impact fluoride removal significantly. For SPL contaminant mixtures, fluoride removal is initially less than expected from idealized, pure, solutions. However, with time, the effect of other contaminants on fluoride removal diminishes. Column tests also show that pH control is important for optimizing fluoride removal with the mass removed increasing with decreasing pH. Barrier pH can be regulated by CO2 addition with the point of injection being critical for optimising the remediation performance. Experimental and model results show that approximately 99% of 2300 mg/L fluoride can be removed when CO2 is injected directly into the barrier. This can be compared to approximately 30-50% removal when the influent solution is equilibrated with atmospheric CO2 before contact with calcite.     

蒸发壁式超临界水氧化反应器处理分散红和活性红染料废水的比较

采用蒸发壁式超临界水氧化反应器对染料分散红C.I.60和活性艳红M-2B配制的模拟废水进行降解实验.实验结果表明,2种染料的COD和TN去除率随着反应温度、氧化剂过量比(r)的升高而上升.COD去除率活性红要高于分散红,而TN去除率则相反.根据GC-MS分析和陶瓷膜SEM图像,分析测得2种染料主要反应中间产物均含有苯酚和苯甲酸,2种染料的反应对陶瓷膜均有轻微的腐蚀.     

新生态MnO2对水溶性阴离子染料废水的脱色研究

以各种水溶性染料,包括直接染料、酸性媒介染料、活性染料的废水为实验对象,系统研究了新生态MnO2在染料废水脱色过程中的作用。结果表明,受试染料的脱色效果均十分显著,最佳pH≤2.5,脱色作用的机理在于MnO2的表面羟基在酸性条件下发生质子化,可以与阴离子染料以库仑力结合而将其吸附除去。     

偶氮染料对斜生栅藻的毒性作用及结构活性相关性研究

为了揭示不同结构染料对水生生态系统的毒性作用,研究９种偶氮类及２种蒽醌类染料对斜生栅藻的生长抑菌作用,并通过剖析毒性一结构之间的相关关系,探讨了偶氮染料的毒作用机理,１１种染产对斜生栅藻的４８ｈＥＣ５０在１．０９－４１．２２ｍｇ．Ｌ＾－１之间,偶氮染料分子中所包含偶氮键的个数及芳香环上取代基的亲水性和电性均影响染料的毒性,进一步证实偶氮染料的毒同理为Ｎ－Ｎ键不宾为一ＮＨ２后,形成Ｎ＋离子活性民生物     

多维电极法处理高色度活性染料模拟废水影响因素分析

以活性嫩黄K 4G染料模拟废水为处理对象 ,采用多维电极法 ,考查了各种因素对多维电极系统处理活性染料时的脱色率、CODCr降解率的影响 ,结果表明 ,增多活性炭量、增大电流密度、延长电解时间和加入铁屑 ,都能使脱色率和CODCr降解率得到提高 ,电导率的变化对脱色率和CODCr降解率有一定影响。利用正交实验比较了各因素的相对影响大小