Adsorption of MCPA pesticide by MgAl-layered double hydroxides

In the present study, the adsorption characteristics of the herbicide MCPA (4-chloro-2-methylphenoxyacetic acid) on layered double hydroxides (LDHs) were evaluated under laboratory conditions with particular attention to the effect of layer charge, original interlayer anion and morphology. The final objective is the use of LDHs and modified LDH materials as recyclable adsorbents and heterogeneous catalysts for the treatment of contaminated waste waters.The anionic clays tested were [Mg_1−xAl_x(OH)₂]^x+[X_x/m^m−·nH₂O] materials. The MCPA adsorption capacity was determined from adsorption isotherms and a kinetic study. We looked at the influence of the pH, the Mg²⁺/Al³⁺ ratio, i.e. the anion exchange capacity, the nature of the intercalated anion X (CO₃²⁻, NO₃⁻, Cl⁻) and the morphology of the adsorbent on the extent of adsorption. The adsorption isotherms, described by Freundlich model, are of S-type with tendency to L-type for high MCPA equilibrium concentration. Furthermore, the adsorption capacity increases with the layer charge density. Hence, MCPA adsorption on LDHs occurs by anion exchange in two steps, an external exchange followed by an interlayer exchange, which explain these changes of type within the same isotherm. Besides, the adsorption capacity depends on the nature of the starting anions, following the affinity order (NO₃⁻<Cl⁻<CO₃²⁻) proposed by Miyata and increases with the specific surface area.     

WSA硫酸装置设计优化

根据国内硫酸装置运行情况,对WSA硫酸装置的设计进行了优化,提出了三项优化措施。采取这些优化措施,可大大减少环境污染,提高经济效益和社会效益。     

Assessment of a redox alkaline/iron-chelate absorption process for the removal of dilute hydrogen sulfide in air emissions

The oxidative absorption of hydrogen sulfide (H₂S) into a solution of ferric chelate of trans-1,2- diaminocyclohexanetetraacetate (CDTA) was studied in a counter-current laboratory column randomly packed with 15 mm plastic Ralu rings. The present investigation takes concern about the Kraft pulping situation where dilute H₂S concentrations are omnipresent in large-volume gas effluents. A fractional two-level factorial approach was instigated to determine the significance of six operating variables, namely the solution's alkalinity (pH; 8.5-10.5), the liquid mass flow rate (L;1.73-), the solution's ionic strength (I_C;0.01-), the gas mass flow rate (G;0.19-), the inlet H₂S concentration (C_H2S,0;70-430 ppm) and the initial ferric CDTA concentration (C_Fe,0;100 -). Initially, a Plackett-Burman design matrix of seven duplicated experiments revealed that pH is the leading factor controlling the H₂S conversion rate while the ionic strength and ferric CDTA concentration effects remained negligible within the factorial domain. Surface response analysis based on 11 duplicated factorial experiments plus 10 central composite trials revealed that the H₂S conversion significantly increases with liquid flow rate but decreases with growing H₂S load up. Further examination about the influence of ferric CDTA on H₂S absorption rate was set up over a broader concentration range (C_Fe,0;0- at pH of 9.5 and 10.5. It showed good potential at as H₂S conversion increased by a significant 25% for both pH values in comparison to pure alkaline solutions containing no ferric CDTA.     

Heat stress management in underground mines

Heat management must be maintained within the mine working environment to minimize stress on equipment and personnel. The issue is a growing concern as mines continue to expand in size, depth and infrastructure. Heat management is a concern as it relates to both heat sensitive equipment and more importantly the health and safety of the workers found within the mine. Proper application of engineering protocols and work practice controls will have a direct impact on the health and safety of workers and increased productivity. Using continuous monitoring stations placed in strategic locations throughout the mine to capture the environmental conditions, various strategies can be used in the planning and prevention of potential hazard exposure. Economic analysis is used to select the most feasible strategy for heat stress control. This paper presents a step by step methodology that may be considered by ventilation specialists to effectively implement a heat management control system. A case study based on a detailed heat management assessment conducted for a potash mine in Saskatchewan, Canada is presented.     

铁矿开采的环境效应

铁矿开采带来的环境问题已日益引起人们的重视。我国铁矿石资源特点利弊参半,矿山开采现状不容乐观。整个矿山开采过程包括采矿、选矿、排岩、尾矿处理,它们对企业周边区域造成了水体污染、植被破坏等诸多环境效应,针对这些问题提出了具有一定参考价值的解决对策。     

浅谈涂料生产企业环境限量物质的控制

简要介绍了涂料生产企业环境限量标准及指令;并分析了各项标准要求,确定环境物质风险,结合企业实际情况进行讲解分析。     

专业导入在环境工程专业英语教学中的实践

环境工程专业英语是以专业需求为基础的实用型英语,属于一门文理兼顾的课程。采用专业导入的模式组织环境工程专业英语的教学工作,是一种新的教学模式。在教学过程中应注意掌握好适度性、实用性和阶段性等几个原则。在教学实践过程中应结合环境工程专业英语的特点,加强对学生阅读专业知识的能力、分析能力、专业知识英汉互译以及听说能力等应用能力的培养。     

脉冲喷吹袋式除尘器在埋弧焊管生产中的应用

针对埋弧焊管生产中焊剂除尘装置存在的问题,设计制造了一种不受气温限制、占地面积小、除尘效果好、工作状态稳定的脉冲除尘装置。该装置确保了焊剂粉尘的有效清除,减轻了环境污染。     

三维环境下CAD/CAPP集成方法研究与实践

三维环境下的CAPP系统集成内容包括产品设计信息和加工工艺信息。这里介绍了三维CAD／CAPP的三种集成方法：基于中间文件集成,基于PDM集成,直接集成。对这几种集成方式进行了分析和比较。作者及所在的课题组应用直接集成的方法,研究与开发的一个基于UG的CAPP原型系统。     

绿色质量功能展开及其应用研究

为了满足顾客对质量、成本和环保的综合要求，需要在产品概念设计阶段充分考虑这三个因素。为此，本文在传统质量功能展开的基础上，将环境因素集成到质量功能展开，形成绿色质量功能展开方法学，并将其分为产品概念分析和最佳产品概念选择两个阶段。随后，给出了它的体系结构和功能展开的详细步骤。最后，以办公桌的质量功能展开为例，对其进行了验证。