环境类型与氯盐浓度对矿渣混凝土表面氯离子浓度的影响

采用化学分析方法测定了掺加10%-70%磨细矿渣的混凝土在青海盐湖卤水、3.5%NaCl＋5%MgSO4溶液和3.5%NaCl溶液等3种氯盐环境中不同暴露时间的自由氯离子浓度分布,研究了不同环境类型与氯盐浓度对矿渣混凝土表面氯离子浓度的影响。结果表明,矿渣混凝土的表面氯离子浓度随着氯盐浓度增大而增大;暴露环境的离子成分越复杂,混凝土表面氯离子浓度越大;矿渣混凝土的表面氯离子浓度随着暴露时间延长呈非线性函数关系增加。

碳钢在不同氯盐浓度下腐蚀速率的研究

为研究碳钢腐蚀速率与氯盐浓度关系,以Q235碳钢为例,采用实验与理论分析相结合的方法,对碳钢在2%、3.5%、5%的NaCl溶液中的腐蚀规律进行研究,分析了碳钢腐蚀速率随氯盐浓度的变化规律。结果表明,在不同氯盐浓度环境中,碳钢的腐蚀速率表现为先减小后趋于稳定;在腐蚀初期,由于Cl-的存在使得碳钢表面钝化膜被迅速破坏,因此腐蚀速率较大,且随氯盐浓度升高而增大;稳定后的碳钢腐蚀速率随氯盐浓度增大表现为先增大后减小,且通过分析得到在氯盐浓度为3.5%时腐蚀速率最大。

表面状态对Q235钢在不同氯离子浓度溶液中电化学腐蚀行为的影响

采用电化学法结合失重法,研究了Q235碳钢电极在质量分数分别为2.0%、3.5%和5.0%的NaCl溶液中的腐蚀行为与腐蚀速率的变化规律。结果表明:碳钢电极表面的腐蚀产物会对电化学实验结果的准确性产生较大的影响。在进行电化学测试前,采用−30μA/cm^(2)恒定电流对碳钢电极进行极化预处理后测得的腐蚀电流密度随Cl^(-)质量分数的增大而表现出先减小后逐渐趋于稳定的变化趋势,修正后的电化学测试结果与失重实验结果能较好地吻合,两者之间的平均误差为5%~9%。通过对腐蚀电极进行阴极极化预处理,令金属表面腐蚀产物进行充分还原,能够有效降低金属表面腐蚀产物对电化学实验结果造成的偏差。

高浓度氯盐环境下钢筋混凝土裂缝扩展影响因素及规律研究

为研究高浓度氯盐环境下钢筋混凝土保护层首次出现裂缝的时间和裂缝宽度扩展规律,采用直流电加速锈蚀法,研究不同电流密度、氯盐浓度、保护层厚度、钢筋直径以及水胶比等因素的影响,探究混凝土裂缝的扩展因素及裂缝扩展规律。结果表明:随电流密度、氯盐浓度、水胶比、钢筋直径增加,锈胀裂缝宽度扩展速度加快;随保护层厚度加厚,锈胀裂缝宽度扩展速度越慢。其中保护层厚度对混凝土裂缝首次开裂的影响最为显著,电流密度和钢筋直径影响次之,氯盐浓度和水胶比的影响相对较小。

氯盐对沥青混合料劈裂抗拉强度影响的试验研究

为了研究盐分浓度对沥青混合料水稳定性的影响,配置了浓度为7%、14%、21%以及28%的盐水,对沥青混合料马歇尔试件进行浸泡,在MQS-2型路面材料强度试验仪上进行冻融劈裂试验,研究不同浓度盐水浸泡过的沥青混合料的水稳定性的变化规律。试验结果表明,经过氯盐侵蚀冻融后,沥青混合料的劈裂抗拉强度明显下降。相同浓度的盐水浸泡后的沥青混合料,随着冻融次数的增加,其冻融劈裂抗拉强度快速下降;而不同浓度的盐水浸泡过的沥青混合料,在相同冻融次数下,冻融劈裂抗拉强度呈逐步下降趋势。

毛细作用下风积沙混凝土水分和氯离子传输特性试验

目的研究毛细作用下水分和氯离子在风积沙混凝土中的传输特性,探讨风积沙掺量、氯盐质量浓度对水分和氯离子侵入的影响规律。方法试验制备了5组不同掺量的风积沙混凝土,按照比例为0%、25%、50%、75%、100%等质量替换普通河砂,通过自然扩散法进行风积沙混凝土毛细吸水/盐试验。结果风积沙混凝土毛细吸收曲线前1 d内均呈线性增长,而后逐渐趋于水平;混凝土在氯化钠溶液中的毛细吸收量和毛细吸收系数大于清水溶液,毛细吸收系数随风积沙掺量的增加呈现先减小后增大的趋势,最小值出现在风积沙掺量为25%。风积沙混凝土中水分和氯离子传输深度呈明显线性关系,当水分传输趋于稳定时,氯离子由于扩散作用依旧向内部传输。通过水分和氯离子侵入深度及两者关系,毛细作用下风积沙混凝土中风积沙掺量宜控制在20%~30%。结论风积沙混凝土中水分和氯离子传输非同步,水分渗透速率大于氯离子渗透速率。当水分渗透逐渐稳定时,氯离子会继续向混凝土内部渗透。

浸泡条件下高韧性水泥基复合材料氯离子侵蚀试验研究

为探究高韧性水泥基复合材料(ECC)在浸泡条件下抵抗氯盐侵蚀的能力,研究开展了ECC的氯离子侵蚀试验。设置0.26、0.28、0.30三种不同水胶比试件,在5wt%、10wt%、16wt%三种氯盐溶液中分别浸泡12 d、30 d、60 d、90 d,用硝酸银溶液对不同情况下的氯离子侵蚀深度进行测试,以此研究水胶比、氯盐浓度以及侵蚀时间对ECC氯离子侵蚀深度的影响规律。结果表明,水胶比越小,ECC基体内部孔隙越少,基体越密实,氯离子侵蚀深度越小;随着氯盐浓度的增大,基体内外浓度差增加,氯离子侵蚀深度随之增大;随着侵蚀时间的增加,浸泡30 d内氯离子侵蚀深度增加较快,后期随着基体内部一系列反应发生,部分孔隙被填充,基体内部有效氯离子传输通道减少,氯离子侵蚀深度增长速度减小,侵蚀深度总体随时间呈现两阶段增长;最后通过回归分析建立氯离子侵蚀深度的预测模型。

Optimization of brine leaching of metals from hydrometallurgical residue

An orthogonal array,L16(45),was used to examine the effects of four parameters,including NaCl concentration,H2SO4 concentration,temperature and pulp density,on the recovery of Cu,In,Pb and Zn from a hydrometallurgical residue via brine leaching.The results show that temperature of leaching solution has a significant effect on the recovery of Cu,In and Zn,while H2SO4 concentration has an obvious influence on these metals extraction.Both pulp density and NaCl concentration significantly affect Pb extraction.Based on the orthogonal array experiments,the optimum conditions for the extraction of Cu,In,Pb and Zn from hydrometallurgical residue are NaCl concentration of 250 g/L,H2SO4 concentration of 1.00 mol/L,temperature of 85℃,and pulp density of 100 g/L.After 1 h of treatment at these optimum conditions,over 91% of the metals are extracted from the residue.Brine leaching is therefore suitable for the recovery of metals from hydrometallurgical residues.

Evaluation of Three Sunflower （Helianthus annuus L.） Hybrids for Salt Tolerance in Vitro

This study aimed to induce callus from three sunflower （Helianthus annulus L.） hybrids, namely Anna, Alhaja and Kuds, and to evaluate their callus for salt stress tolerance. Cotyledons and hypocotyl were taken from seedling of these hybrids and cultured on MS media contained 2,4-D （0,0, 0.5, 1.0, 1.5 and 2.0 mg/L） and kinetin （0.0, 0.5, and 1.0 mg/L）. The cultures incubated at 25 ＋ I^C under light condition （1,000 Lux） for 16 h/day. After 6 weeks observations were taken on the response of cotyledons and hypocotyl to callus induction. The induced callus were cultured on the same MS media that contained appropriate concentrations of 2,4-D and kinetin for callus induction as well as contained various concentration of sodium chloride NaCI （0.0, 0.05, 0.1, 0.15 and 0.2%）. After six weeks callus fresh and dry weights, proline and total carbohydrates concentrations were measured. The results showed significant differences among the hybrids, explants, 2,4-D and kinetin concentration and significant interaction between them in their percentage response for callus induction. The results also revealed that fresh and dry weights were significantly reduced with increased NaCI concentration in the medium, hybrids showed significant differences in their response to salt stress. Proline and total carbohydrate concentration increased in callus as NaCI increased in the media. Significant interaction was showed between hybrids and NaCI concentration in these parameters.

Salinization:the ultimate threat to temperate lakes,with particular reference to Southeastern Wisconsin(USA)

Many lakes in Southeastern Wisconsin(the metropolitan-Milwaukee area) are gradually becoming increasingly "salty".While these waterbodies would not be considered presently to be saline lakes,there has been a rapid increase in the chloride concentrations in most of these lakes over the last 30 years,with the lakes increasing from a mean chloride concentration of about 19 mg/L to over 100 mg/L in some cases.While ecological impacts can be expected when chloride values exceed 250 mg/L,the rate of increase presents a basis for concern,especially since the underlying geology of the region is based on limestone/dolomite which is deficient in chlorides.Thus,the origin of the chlorides is anthropogenic:human and industrial wastewaters(treatment of which has effected improvements in trophic status but has not affected other water-borne contaminants) and winter de-icing practices based upon large quantities of sodium chloride are major contributors to the increasing concentrations of chloride in the region's waterways.Without taking remedial measures,the rate of salinization is expected to continue to increase,resulting,ultimately,in the alteration of the freshwater systems in the region.

Aerobic Biodegradation of Chlorinated Hydrocarbons by Bacillus circulans WZ-12 CCTCC M 207006 under Saline Conditions

A novel saline-tolerant bacterium Bacillus circulans WZ-12 was evaluated for its potential to degrade four chlorinated hydrocarbons under saline conditions. CHECl2 was effectively degraded by Bacillus circulans WZ-12 cells in the medium containing NaCl concentrations ranging from 5 g.L^-1 to 10 g-L^-1, and the maximum degradation efficiency （85%） was achieved at NaCl concentration of 10 g.L^-1. Similarly, Bacillus circulans WZ-12 was able to degrade CH2BrCl, C2H4Cl2, and C2H2Cl2 in the presence of 10 g NaCl per liter within 24 h. Cells of Bacillus circulans WZ-12 grown in minimal salt medium contained low levels of glycine betaine （GB）, but GB levels were 3- to 5-fold higher in cells grown in media with high salt. Kinetic analysis revealed that biodegradation of the four chlorinated hydrocarbons was concentration dependent and a linear inverse correlation （R2= 0.85-0.94） was observed between the rate of biodegradation （V） and salt concentration from 5 g.L〈 to 60 g.L-1. The growing cells （in minimal salt medium） degraded approximately 50% of the CH2C12 within 24 h, whereas the resting cells （in physiological saline） degraded only 25% of the CH2C12 within 24 h and were inactive after 36 h cultivation. Biodegradation could be repeatedly performed for more than 192 h with more than 50% removal efficiency. Bacillus circulans WZ-12 grows well in an aqueous/oil system, hence, it is effective for the treatment of industriai efflu- ents that contain chlorinated hydrocarbons with high salt concentrations.