海藻酸钠-钙-铁凝胶球对Cr_2O_7~(2-)吸附的研究

本实验对海藻酸钠在氯化钙、氯化铁溶液中的成球特性,以及对SA-Ca、SA-Fe、SA-Ca-Fe凝胶球吸附Cr2O72-特性进行了研究。结果表明,SA-Ca凝胶球对Cr2O72-没有吸附能力,SA-Fe和SA-Ca-Fe凝胶球对Cr2O72-去除率均达到97%以上,但SA-Fe凝胶球成球性差,机械强度低,易碎。SA-Ca-Fe凝胶球吸附Cr2O72-符合Langmuir型,其最大吸附量为13.497mg/g。吸附属于单分子层吸附,凝胶球网络中的Fe3+与溶液中Cr2O72-发生化学反应,生成Fe2(Cr2O7)3。     

高铁酸钾处理水中十六烷基三甲基溴化铵

室温条件下采用新型氧化剂高铁酸钾(K2FeO4)处理十六烷基三甲基溴化铵(CTAB)模拟废水,探讨反应时间、K2FeO4投加量及体系pH值等因素对CTAB去除率的影响.结果表明,反应时间、K2FeO4投加量及溶液pH值对CTAB的去除率均有不同程度的影响,当反应时间为30 min、K2FeO4投加量与处理液中CTAB质量比为1∶1、溶液pH为7时,K2FeO4对表面活性剂CTAB的去除率达79.4%.在反应过程中,K2FeO4的强氧化性与其还原产物的絮凝作用产生协同效应,其中K2FeO4在完全反应之前CTAB的去除主要依靠K2FeO4的强氧化作用,K2FeO4反应完全之后CTAB的去除则主要依靠K2FeO4还原产物的絮凝作用.同时进一步研究了CTAB被处理前后的红外光谱特征,结果表明CTAB在降解过程中经历了链的断裂并进一步被矿化为无机小分子.化学反应动力学研究结果表明K2FeO4与CTAB的反应符合二级反应动力学规律.     

Fe(Ⅵ)在光催化条件下的分解及协同光催化降解BPA的研究

研究了不同条件下Fe(Ⅵ)-光催化氧化方法对双酚A (BPA)的降解作用.结果表明,在光催化氧化中,TiO₂表面产生的光生电子(e^-_cb)会将Fe(Ⅵ)还原成Fe(Ⅴ)和Fe(Ⅳ),Fe(Ⅵ)的加入对光催化氧化起到了协同作用,提高了光催化氧化的效率.此外,还研究了Fe(Ⅵ)在不同条件下的分解情况,发现光催化氧化能促进Fe(Ⅵ)的分解,随着pH值的增加,TiO₂表面吸附Fe(Ⅵ)的能力减弱.采用光催化氧化方法降解BPA时,加入Fe(Ⅵ)可以提高BPA的氧化降解速率2.5倍.     

Uptake of Cs by berries, mushrooms and needles of Scots pine in peatland forests after wood ash application

Increasing use of wood fuels for energy production in Finland since the 1990s implies that large quantities of the generated ashes will be available for forest fertilization. The aim of this study was to analyse the effect of wood ash application on ¹³⁷Cs activity concentrations in Scots pine (Pinus sylvestris L.) needles and certain berries and mushrooms on drained peatlands. The study was based on field experiments carried out on two mires in Finland in 1997-1998. Two different types of wood ash were applied at dosages of 3500, 3700, 10 500 and 11 100 kg ha⁻¹. Wood ash did not increase ¹³⁷Cs activity concentration in plants in the second growing season following application. On the contrary, a decrease in ¹³⁷Cs activity concentration was seen in the plants of the ecosystem on drained peatlands. This result is of importance, for instance, when recycling of ash is being planned.     

Simultaneous removal of phosphorus and potassium from synthetic urine through the precipitation of magnesium potassium phosphate hexahydrate

This study investigated the simultaneous removal of P and K from synthetic urine through the precipitation of magnesium potassium phosphate hexahydrate (MPP, MgKPO₄·6H₂O) in bench-scale experiments. Results show that the removal efficiencies of P and K are mainly determined by the solution pH and the molar ratio of Mg:K:P. Co-precipitation of struvite-type compounds, i.e., magnesium ammonium phosphate hexahydrate (MAP, MgNH₄PO₄·6H₂O), magnesium sodium phosphate heptahydrate (MSP, MgNaPO₄·7H₂O), and MPP, was confirmed by analysis of the solid precipitates using a Scanning Electron Microscope/Energy Dispersive X-ray Apparatus and an X-ray Diffractometer. The co-precipitation significantly influenced the removal of K. As much ammonium as possible should be removed prior to MPP precipitation because MAP had higher tendency to form than MPP. The inevitable co-precipitation of MPP and MSP resulted in the addition of more MgCl₂·6H₂O and Na₂HPO₄·12H₂O to obtain the high removal of K. In total, the removal efficiencies of P and K were 77% and 98%, respectively, in the absence of ammonium when pH was 10 and the molar ratio of Mg:K:P was 2:1:2. The results indicate that the MPP precipitation is an efficient method for the simultaneous removal of P and K to yield multi-nutrient products.     

Characteristics and applications of controlled-release KMnO4 for groundwater remediation

In situ chemical oxidation (ISCO) using potassium permanganate (KMnO4) has been widely used as a practical approach for remediation of groundwater contaminated by chlorinated solvents like trichloroethylene. The most common applications are active flushing schemes, which target the destruction of some contaminant source by injecting concentrated permanganate (MnO4(-)) solution into the subsurface over a short period of time. Despite many promising results, KMnO4 flushing is often frustrated by inefficiency associated with pore plugging by MnO2 and bypassing. Opportunities exist for the development of new ISCO systems based on KMnO4. The new scheme described in this paper uses controlled-release KMnO4 (CRP) as an active component in the well-based reactive barrier system. This scheme operates to control spreading of a dissolved contaminant plume. Prototype CRP was manufactured by dispersing fine KMnO4 granules in liquid crystal polymer resin matrix. Scanning electron microscope data verified the formation of micro-scale (ID=20-200 microm) secondary capillary permeability through which MnO4(-) is released by a reaction-diffusion process. Column and numerical simulation data indicated that the CRP could deliver MnO4(-) in a controlled manner for several years without replenishment. A proof-of-concept flow-tank experiment and model simulations suggested that the CRP scheme could potentially be developed as a practical approach for in situ remediation of contaminated aquifers. This scheme may be suitable for remediation of sites where accessibility is limited or some low-concentration contaminant plume is extensive. Development of delivery systems that can facilitate lateral spreading and mixing of MnO4(-) with the contaminant plume is warranted.     

化学氧化法制备高铁酸钾循环生产可能性的试验

本文研究了回收利用湿法制备Ｋ２ＦｅＯ４晶体后的残留母液,制取次氯酸盐混合溶液,氧化Ｆｅ（Ⅲ）－→Ｆｅ（Ⅵ）的方法,探讨了混合次氯酸盐浓度、铁盐添加量、反应体系碱浓度等对高铁转化率的影响。     

高铁酸盐对2种水源水中藻类的去除效果

研究了高铁酸盐对深圳2种原水水中藻类的去除效能.实验结果表明,在处理以小球藻为主的东湖水时,单纯PAC混凝就可有效地去除水中的藻类,藻类去除率均在95%左右.在处理含藻量多,以颤藻为主的铁岗原水时,单纯PAC混凝除藻效果不理想,投加少量高铁酸盐进行预氧化,再投加PAC混凝,可使水中藻的去除率提高10%～20%,去除率高达97.85%.而且用高铁预氧化除藻法明显优于传统预氯化方法.     

绿色水处理剂高铁酸盐在水处理领域中的应用进展

高铁酸盐是饮用水和废水处理中一种多功能绿色环保水处理剂,因其具有高效的氧化、混凝、消毒杀菌能力,且不产生有毒有害的物质,在水处理领域中已受到广泛关注.为全面、系统地剖析高铁酸盐在水处理领域中现有的研究成果,运用知识图谱分析工具VOSviewer对来自中国知网(CNKI)数据库和Webof Science(WOS)数据库...     

Post-combustion CO2-capture from coal-fired power plants: Preliminary evaluation of an integrated chemical absorption process with piperazine-promoted potassium carbonate

The simulation tool ASPEN Plus^® is used to model the full CO₂-capture process for chemical absorption of CO₂ by piperazine-promoted potassium carbonate (K₂CO₃/PZ) and the subsequent CO₂-compression train. Sensitivity analysis of lean loading, desorber pressure and CO₂-capture rate are performed for various solvent compositions to evaluate the optimal process parameters. EbsilonProfessional^® is used to model a 600 MW_el (gross) hard coal-fired power plant. Numerical equations for power losses due to steam extraction for solvent regeneration are derived from simulation runs. The results of the simulation campaigns are used to find the process parameters that show the lowest specific power loss. Subsequently, absorber and desorber columns are dimensioned to evaluate investment costs for these main components of the CO₂-capture process. Regeneration heat duty, net efficiency losses and column investment costs are then compared to the reference case of CO₂-capture by monoethanolamine (MEA).CO₂-capture by piperazine-promoted potassium carbonate with subsequent CO₂-compression to 110 bar shows energetic advantages over the reference process which uses MEA. Additionally, investment costs for the main components in the CO₂-capture process (absorber and desorber columns) are lower due to the enhanced reaction kinetics of the investigated K₂CO₃/PZ solvent which leads to smaller component sizes.