Response surface method for modeling the removal of carbon dioxide from a simulated gas using water absorption enhanced with a liquid-film-forming device

This paper presents the results from using a physical absorption process to absorb gaseous CO_2mixed with N_2using water by producing tiny bubbles via a liquid-film-forming device(LFFD)that improves the solubility of CO_2in water.The influence of various parameters—pressure,initial CO_2concentration,gas-to-liquid ratios,and temperature—on the CO_2removal efficiency and its absorption rate in water were investigated and estimated thoroughly by statistical polynomial models obtained by the utilization of the response surface method(RSM)with a central composite design(CCD).Based on the analysis,a high efficiency of CO_2capture can be reached in conditions such as low pressure,high CO_2concentration at the inlet,low gas/liquid ratio,and low temperature.For instance,the highest removal efficiency in the RSM–CCD experimental matrix of nearly 80%occurred for run number 20,which was conducted at 0.30 MPa,CO_2concentration of 35%,gas/liquid ratio of 0.71,and temperature of 15°C.Furthermore,the coefficients of determination,R~2,were 0.996 for the removal rate and 0.982 for the absorption rate,implying that the predicted values computed by the constructed models correlate strongly and fit well with the experimental values.The results obtained provide essential information for implementing this method properly and effectively and contribute a promising approach to the problem of CO_2capture in air pollution treatment.     

微分电位溶出法测定空气和水中微量铅

本文研究了在镀汞、银汞电极上铅的溶出行为 ,当 p H为 3.0～ 6 .0时 ,在乙酸钠——乙酸溶液中 ,铅的溶出电位为 - 0 .44 5 V,具有良好的溶出峰形。并且建立了用微分电位溶出银汞电极分析空气和水中微量铅的方法 ,该法克服了玻碳电极法反复镀汞的麻烦。本方法对四份水样进行回收率试验 ,其回收率均在 90 %以上 ,变异系数小于 10 %。因此该法具有较好的精密度和准确性     

几种低分子量有机酸对石灰岩溶蚀作用的室内模拟试验

在室内进行了几种低分子量有机酸对石灰岩颗粒(粒径0.45～1mm)的溶蚀试验,同时用盐酸进行对比试验。结果表明:各有机酸对石灰岩颗粒溶蚀作用大小的顺序为:乳酸>乙酸>柠檬酸>甲酸>草酸>丙酮酸,同类型酸中如醇酸或羧酸中,酸性较弱的酸溶蚀力反而较大。这几种酸混合后对石灰岩颗粒的溶蚀作用并未比单个酸的作用强。乳酸、乙酸、柠檬酸的溶蚀力大于盐酸。不管是有机酸还是盐酸,溶蚀石灰岩后溶液中钙离子浓度都呈对数增长,且与溶液pH值呈极显著正相关(P<0.0001);草酸反应液中的钙离子浓度与电导值呈极显著负相关(P<0.0001),其他种类酸溶液钙离子浓度则与电导值呈极显著正相关;除乙酸外,其他酸溶液电导值在反应初始阶段稍微下降后迅速上升。有机酸对石灰岩的溶蚀能力不仅与溶液中的H+和有机配位体浓度有关,而且与酸的类型、酸的强弱及反应后形成的盐的溶解度有关。     

New approach to studies of heavy metal redistribution in soil

The bioavailability and mobility of heavy metals in soils is dependent upon redistribution processes between solution and solid phases and among solid-phase components. This paper reviews the definitions and applications of two newly developed parameters, the redistribution index and the reduced partitioning parameter, in quantifying redistribution processes of heavy metals in contaminated soils. The redistribution index depicts the removal/attainment of metal-contaminated soils from/to the fractional distribution pattern characteristic of non-amended soils, while the reduced partitioning parameter quantifies the relative binding intensity of heavy metals in soils. Over time, metal salt-spiked and sludge-amended soils approached the fractional distribution pattern of non-amended soils. The rates of redistribution of metals and their binding intensity in soils were affected by the metal species, loading levels and soil properties. Metals in contaminated soils at low loading levels approach the fractional distribution pattern of non-amended soil more rapidly than those at high loading levels. The sequence order of approach by metals to the fractional distribution pattern of non-amended soil was: Cd>Cu>Ni=Zn>Cr. In both non-amended and contaminated soils, Cr had the highest binding intensity, Cd the lowest, and Cu, Ni and Zn, intermediate values. In addition to our own data, primarily on metal salt-spiked soils, these two indices are also used to evaluate redistribution processes of heavy metals in sewage sludge-amended soils from other published reports.     

Arsenic release from flooded paddy soils is influenced by speciation, Eh, pH, and iron dissolution

Arsenic (As) is highly mobilized when paddy soil is flooded, causing increased uptake of As by rice. We investigated factors controlling soil-to-solution partitioning of As under anaerobic conditions. Changes in As and iron (Fe) speciation due to flooded incubation of two paddy soils (soils A and B) were investigated by HPLC/ICP-MS and XANES. The flooded incubation resulted in a decrease in Eh, a rise in pH, and an increase in the As(III) fraction in the soil solid phase up to 80% of the total As in the soils. The solution-to-soil ratio of As(III) and As(V) (R_L/S) increased with pH due to the flooded incubation. The R_L/S for As(III) was higher than that for As(V), indicating that As(III) was more readily released from soil to solution than was As(V). Despite the small differences in As concentrations between the two soils, the amount of As dissolved by anaerobic incubation was lower in soil A. With the development of anaerobic conditions, Fe(II) remained in the soil solid phase as the secondary mineral siderite, and a smaller amount of Fe was dissolved from soil A than from soil B. The dissolution of Fe minerals rather than redox reaction of As(V) to As(III) explained the different dissolution amounts of As in the two paddy soils. Anaerobic incubation for 30 d after the incomplete suppression of microbial activity caused a drop in Eh. However, this decline in Eh did not induce the transformation of As(V) to As(III) in either the soil solid or solution phases, and the dissolution of As was limited. Microbial activity was necessary for the reductive reaction of As(V) to As(III) even when Eh reached the condition necessary for the dominance of As(III). Ratios of released As to Fe from the soils were decreased with incubation time during both anaerobic incubation and abiotic dissolution by sodium ascorbate, suggesting that a larger amount of As was associated with an easily soluble fraction of Fe (hydr) oxide in amorphous phase and/or smaller particles.     

A pore-scale investigation of mass transport from dissolving DNAPL droplets

Spheres and pendular rings of trichloroethylene and tetrachloroethylene are observed dissolving in an artificial porous medium consisting of a single layer of glass beads. Given the simple geometry of the droplets, pore-scale mass transfer coefficients are calculated. For dissolving spheres, mass transfer coefficients are found to be constant over time. However, coefficients for pendular rings are found to decrease as the rings shrink in size. This is consistent with the concept of diffusion-controlled mass transfer in low-flow zones. Sherwood numbers measured at Reynolds numbers between 0.0033 and 8.33 show a similar trend to empirical relationships established by previous researchers using other techniques. As in previous experiments, considerable scatter in mass transfer rates is observed at a given mean flux. It is hypothesized that this variation in local mass transfer rates is caused by variations in local pore velocity.     

微波辅助生物淋滤废旧碱性电池锌锰的溶出

以氧化硫硫杆菌为淋滤菌株对废旧碱性电池电极材料中Zn、Mn进行生物淋滤,考察了生物淋滤、化学浸提和微波辅助处理对Zn、Mn浸出率的影响。实验结果表明,在能源底物单质硫浓度20 g/L、初始pH值1.0、淋滤培养温度35℃、固液比为1%条件下,经过9 d生物淋滤,微波辅助处理的生物淋滤体系Zn、Mn浸出率均达到49%左右,优于其他淋滤体系。溶出动力学研究表明,Zn的溶出动力学符合化学反应控制模型,Mn的溶出则表现较为复杂。此外,SEM-EDS、XRD分析可知,原样经过微波辐照,部分ZnMn2O4分解为MnO,促进了Mn的溶出。     

水热预处理对污泥理化性质的影响

剩余污泥进行水热预处理时,研究了水热温度、时间和污泥固液比对污泥理化性质的影响?。结果表明：随着水热温度的升高,COD_Cr溶出率和污泥减量化程度逐渐提高,200 ℃时,COD_Cr溶出率最大,较原泥提高了96.5%,污泥减量化最大为80.1%,氨氮呈不规则性变化;水热时间对污泥减量化和氨氮溶出影响较小,当水热时间为1 h时,污泥中COD_Cr溶出率最大,较原泥提高了96.5%;固液比为10%,水热预处理后污泥中氨氮溶出最小,为1.093 mg/g。通过考察3个因素对污泥理化性质的影响,得出最佳水热预处理条件为污泥固液比为10%时,在200 ℃下,水热1 h后,污泥预处理效果最好,COD_Cr溶出率可达到最大值。     

含铁颗粒物的溶解动力学研究进展

气溶胶沉降是开放大洋可溶性铁的主要来源之一,对海洋初级生产力有重要影响.目前气溶胶可溶性铁的沉降通量仍存在很大的不确定性.主要原因包括:(1)不同来源的气溶胶中可溶性铁的含量差异较大;(2)发生在大气传输中的化学反应能够显著影响气溶胶中铁元素的可溶性.本文总结了过去20a国内外关于含铁颗粒物溶解动力学实验室研究的主要结...