膨润土改性及对水中Cr(Ⅵ)吸附性能的研究

目的 提高膨润土对水中Cr（Ⅵ）的吸附性能。方法 采用氢氧化钠和壳聚糖对膨润土进行改性，分别得到碱改性膨润土（B-NaOH）、壳化膨润土（B-CS）和壳化碱改性膨润土（B-NaOH-CS）。以钠基膨润土（B）为对照，利用红外光谱仪、扫描电镜和比表面积分析仪表征3种改性膨润土的理化性质，研究其对Cr（Ⅵ）的吸附性能。结果 B-NaOH-CS中出现了强N—H吸收峰以及增强的C—H对称弯曲峰，同时B-NaOH-CS表面片状结构卷曲分散，层间孔隙增多，比表面积是其他膨润土的1.2倍以上。当Cr（Ⅵ）质量浓度为50 mg·L^-1时，B-NaOH-CS对Cr（Ⅵ）的平衡吸附量为1.03 mg·g^-1，分别是B-CS、B-NaOH的1.26、1.84倍。描述膨润土吸附Cr（Ⅵ）的动力学过程，准二级动力学模型优于准一级动力学模型；描述膨润土吸附Cr（Ⅵ）的热力学过程，Langmuir等温模型优于Freundlich等温模型。热力学参数△H>0、△G<0、△S>0，表明膨润土吸附Cr（Ⅵ）为吸热、自发、无序反应。B-NaOH在pH=7.0时对Cr（Ⅵ）的吸附量最大，B-CS、B-NaOH-CS在pH = 3.0时对Cr（Ⅵ）的吸附量最大。结论 B-NaOH-CS对Cr（Ⅵ）的吸附效果最好，改性膨润土对去除Cr（Ⅵ）污染有重要作用。     

竹活性炭处理六价铬废水的试验研究

用竹子加工的下脚料制得的竹活性炭,对六价铬废水进行净化处理。结果表明,竹活性炭对六价铬废水处理效果良好,实验探讨了竹活性炭处理六价铬废水的一般规律及影响因素。     

Sorption of Cr(VI) on the wood of Japanese larch treated with concentrated sulfuric acid

A carbonaceous sorbent was prepared from the wood of Japanese larch (Larix leptolepis) by dehydration with concentrated sulfuric acid in a 69% yield. The abilities of the sorbent to remove Cr(VI) from aqueous solutions were investigated. Research parameters included the initial solution pH, temperature, and initial concentration of Cr(VI) in solution. The removal of Cr(VI) was highly solution pH dependent and was mainly governed by physicochemical sorption under weak acidic conditions. The equilibrium data fit well in the Langmuir isotherm model. The Langmuir constants were calculated at different temperatures, and the sorption capacity increased with rising temperature, indicating the endothermic nature of the Cr(VI) sorption onto the sorbent. The desorption experiments suggest that the Cr(VI) sorption is generally irreversible, owing to strong interaction of HCrO ₄ ⁻ with the active sites of the sorbent.     

Work-hardening Mechanism of Non-magnetic High Manganese ZG25Mn18Cr4 Castings

The important character of non-magnetic high manganese ZG25 Mn18Cr4 alloy is rapid work-hardening under external stress. With X-ray diffraction and TEM analysis, it is proved that the microstructures of both undeformed and deformed matrixes are austenite and carbide with some striation structure in the matrixes, the amount of stripes in the deformed matrix is obviously more than that in the undeformed matrix. Electronic diffraction analysis confirmed that the stripes in coarse austenite grains are high density lamination fault sheets. A great deal of lamination fault sheets produced by plastic deformation divides up austenite matrix, shortens the free distance of dislocation movement and results in the rapid work-hardening of ZG25Mn18Cr4 alloy.     

重铬酸钾胁迫对植物根尖细胞的损伤

研究了重铬酸钾对植物根尖细胞的损伤。实验结果表明，重铬酸钾可以抑制植物幼苗的生长，引起植物根尖细胞ＤＮＡ的损伤和导致细胞的超微结构发生改变，此外，过氧化物酶同工酶谱的带型经重铬酸诱导后也呈现很大变化。以上诸变化与处理的重铬酸钾浓度和处理的时间长短密切相关。     

螯合剂对沉积物中铬的去向的影响

A laboratory investigation on reaction between chelating agents and chromium was conducted to evaluate the effect of chelating agents on the adsorption and desorption of chromium in sediment. The amount of adsorbed chromium(Ⅵ) in sediment decreased slightly by 5%-10% because of addition of chelating agents. Chelating agents inhibited the removal of Cr(Ⅲ) by sediment from solutions and the inhibiting effect was in the order: citric acid > tartaric acid > EDTA, salicylic acid. No effect of chelating agents on desorption of chromium in sediment was observed.     

微波固相法合成蛋氨酸螯合铬及其品质分析

试验以蛋氨酸和六水氯化铬为原料,研究微波固相法合成氨基酸螯合铬的最佳工艺条件,并对产品进行理化分析。结果表明,最佳工艺参数为配体摩尔比3:1,微波功率600w,微波辐射时间150s,引发水剂量20mL,此条件下产率可达到56.7%。采用红外光谱分析,确认所制的产品为络合盐。试验结果表明螯合率为82.1%,产品纯度为91%,其中蛋氨酸含量为86.63%,Cr含量为11.50%。在水溶液中蛋氨酸螯合铬比较稳定;在生理条件下,产品溶解性较好。     

模拟降雨条件下污染土壤中重金属元素径流迁移特征

探明污染土壤中重金属元素随地表径流迁移特征,对于防控重金属污染物的迁移扩散具有重要意义。通过室内模拟降雨试验,研究不同降雨强度下(55,100,120mm/h)污染土壤中Cd、Pb和Cr随地表径流迁移的特征。结果表明:径流中3种重金属元素总量在产流的前20min内逐渐降低,随后趋于稳定;产流初期(产流10min内)颗粒态重金属占径流重金属总量的比例均在80%以上;随产流时间延长,颗粒态Cd和Cr对径流重金属的贡献率快速降低,其颗粒态/溶解态的比值范围分别为47.0～0.4和12.9～0.4,而Pb则主要以颗粒态的形式存在,溶解态Pb对其随径流迁移的贡献率可忽略不计;随降雨强度增大,径流中总Cd和Pb含量显著降低,而径流中总Cr含量以及溶解态重金属含量无明显变化规律。     

铬胁迫对辣椒幼苗生长和生理生化特性的影响

[目的]探讨铬胁迫对茄果类蔬菜的毒害机理。[方法]通过水培试验,研究0(对照)、5、10、20、50和100 mg/L的K2Cr2O7Cr溶液对辣椒幼苗生长和生理的影响。[结果]随着Cr6+浓度的升高,辣椒幼苗的生长受到了明显的抑制,株高、根部和地上部的鲜重、干重显著降低,根冠比(干重)呈升高趋势,叶绿素含量、叶绿素a/b值呈下降趋势,细胞膜透性大幅度增大,丙二醛(MDA)含量显著升高,超氧化物歧化酶(SOD)活性下降,过氧化物酶(POD)活性先上升后下降。Cr6+浓度与根部和地上部的干重、叶绿素a含量均呈极显著的负相关,与叶绿素b含量呈显著的负相关。[结论]辣椒幼苗对低浓度的Cr6+具有一定的抵抗作用。