Influence of ionic strength and pH on the limitation of latex microsphere deposition sites on iron-oxide coated sand by humic acid

This study, for the first time, investigates and quantifies the influence of slight changes in solution pH and ionic strength (IS) on colloidal microsphere deposition site coverage by Suwannee River Humic Acid (SRHA) in a column matrix packed with saturated iron-oxide coated sand.Triple pulse experimental (TPE) results show adsorbed SRHA enhances microsphere mobility more at higher pH and lower IS and covers more sites than at higher IS and lower pH. Random sequential adsorption (RSA) modelling of experimental data suggests 1 μg of adsorbed SRHA occupied 9.28 ± 0.03 × 10⁹ sites at pH7.6 and IS of 1.6 mMol but covered 2.75 ± 0.2 × 10⁹ sites at pH6.3 and IS of 20 mMol. Experimental responses are suspected to arise from molecular conformation changes whereby SRHA extends more at higher pH and lower ionic strength but is more compact at lower pH and higher IS. Results suggest effects of pH and IS on regulating SRHA conformation were additive.     

Changes in mineralogical and leaching properties of converter steel slag resulting from accelerated carbonation at low CO2 pressure

Steel slag can be applied as substitute for natural aggregates in construction applications. The material imposes a high pH (typically 12.5) and low redox potential (Eh), which may lead to environmental problems in specific application scenarios. The aim of this study is to investigate the potential of accelerated steel slag carbonation, at relatively low pCO₂ pressure (0.2 bar), to improve the environmental pH and the leaching properties of steel slag, with specific focus on the leaching of vanadium. Carbonation experiments are performed in laboratory columns with steel slag under water-saturated and -unsaturated conditions and temperatures between 5 and 90 °C. Two types of steel slag are tested; free lime containing (K3) slag and K1 slag with a very low free lime content. The fresh and carbonated slag samples are investigated using a combination of leaching experiments, geochemical modelling of leaching mechanisms and microscopic/mineralogical analysis, in order to identify the major processes that control the slag pH and resulting V leaching. The major changes in the amount of sequestered CO₂ and the resulting pH reduction occurred within 24 h, the free lime containing slag (K3-slag) being more prone to carbonation than the slag with lower free lime content (K1-slag). While carbonation at these conditions was found to occur predominantly at the surface of the slag grains, the formation of cracks was observed in carbonated K3 slag, suggesting that free lime in the interior of slag grains had also reacted. The pH of the K3 slag (originally pH ± 12.5) was reduced by about 1.5 units, while the K1 slag showed a smaller decrease in pH from about 11.7 to 11.1. However, the pH reduction after carbonation of the K3 slag was observed to lead to an increased V-leaching. Vanadium leaching from the K1 slag resulted in levels above the limit values of the Dutch Soil Quality Decree, for both the untreated and carbonated slag. V-leaching from the carbonated K3 slag remained below these limit values at the relatively high pH that remained after carbonation. The V-bearing di-Ca silicate (C2S) phase has been identified as the major source of the V-leaching. It is shown that the dissolution of this mineral is limited in fresh steel slag, but strongly enhanced by carbonation, which causes the observed enhanced release of V from the K3 slag. The obtained insights in the mineral transformation reactions and their effect on pH and V-leaching provide guidance for further improvement of an accelerated carbonation technology.     

铬渣无害化处理技术研究进展

综述了铬渣无害化处理技术的研究进展,分析了各种技术在实际应用过程中的效果,指出各种处理技术的优缺点,详细介绍了固化法中水泥固化和药剂稳定化两种处理技术,提出开发重金属螯合剂是今后铬渣稳定化处理的研究方向.     

PBTCA稳定零价纳米铁的制备及其去除水中Cr(Ⅵ)

以2-膦酸丁烷-1,2,4三羧酸(PBTCA)为稳定剂,通过FeCl3.6H2O与NaBH4反应,利用液相还原法制备稳定纳米级零价铁颗粒(P-NZVI),并用透射电子显微镜(TEM)、扫描电子显微镜(SEM)及X射线衍射(XRD)进行表征,颗粒平均粒径为73 nm。考察了Cr(Ⅵ)溶液初始浓度、pH、NZVI投加量、温度等条件对Cr(Ⅵ)去除效果的影响,并与同等条件下不加稳定剂制备的纳米铁(N-NZVI)进行对比。结果表明:Cr(Ⅵ)的去除率随温度和纳米铁投加量增加而升高,随pH和Cr(Ⅵ)溶液初始浓度升高而降低。在相同实验条件下,P-NZVI对Cr(Ⅵ)的去除效果明显优于N-NZVI,表明改性后纳米铁在地表水原位修复领域具有较好的应用前景。     

Concentration of some heavy metals in organically grown primitive,old and modern wheat genotypes: Implications for human health

The concentration of six HMs (Cd, Cr, Co, Pb, Hg and Ni) was analysed in 321 organically grown winter and spring wheat genotypes from six genotype groups, i.e. selections, old landraces, primitive wheat, spelt, old cultivars and cultivars. Also the potential risk of individual toxic HM to human health was estimated by using the Hazard Quotient (HQ). Significantly the lowest grain concentration of Cd was found in primitive wheat as compared to all other investigated genotype groups. Intake of HM by consumption of whole wheat grain was not found to pose a health risk to human for any of the investigated genotype groups. The bio-concentration factor of Cd for the different genotype groups indicated a lower ability to accumulate Cd for primitive wheat as compared to other genotype groups. The primitive wheat was found the most promising and might be of interest in future wheat breeding programs to develop wheat genotypes with low HMs concentration in the grain.     

两株镉抗性奇异变形杆菌对龙葵修复镉污染土壤的强化作用

以广东省大宝山尾矿区植物根际土壤为分离样品,人工制备镉污染LB培养基,从中分离筛选出2株具有较强镉耐受能力的细菌,分别为TL3和DBS2,最高镉耐受浓度达300mg／L。结合其形态学特征、生理生化特性及16SrDNA序列分析,初步确定2株菌均为奇异变形杆菌（Proteusmirabilis）。随后以龙葵为实验植株,分别接种TL3、DBS2及TL3与DBS2混菌的培养液,通过盆栽实验检验2株菌对龙葵吸收土壤中镉的强化作用。结果显示,2株菌对龙葵吸收镉具有显著的提升作用,且能够促进植株的生长,3个实验组龙葵根部镉含量分别比对照组（122．7mg／kg）增加了17．2％、85．6％和130．1％。     

含砷冶炼废渣高温烧结过程砷的迁移特性

研究了烧结温度和烧结时间对含砷冶炼废渣烧结过程中砷的迁移特性的影响。烧结条件为在10 MPa下加压成型,进空气流量为2 000 mL/min,烧结温度1 000～1 350℃,烧结时间5～120 min。结果表明,烧结过程中存在砷的挥发,但烧结前后砷的总量变化不大,砷的固化率均保持在90%以上。毒性浸出实验表明,不同的烧结条件对烧结体中砷的毒性浸出有重要的影响,从烧结体的环境安全性考虑,最佳的烧结温度和时间分别为1 200℃和45 min。     

铝污泥吸附六价铬的特征和机理

铝污泥是给水处理过程中不可避免的副产物,为了解其资源化利用作为吸附剂对Cr(Ⅵ)的吸附行为和吸附特征,本研究通过静态实验研究了铝污泥的水解特征、Cr(Ⅵ)在铝污泥上的吸附机理和影响因素。结果表明,(1)铝污泥表面的主要官能团为羟基、SO24-和Cl-;(2)铝污泥与Cr(Ⅵ)的吸附过程中,液相中Cr(Ⅵ)的浓度随吸附时间延长而降低(由20 mg/L降为15.42 mg/L),同时,液相中pH由6.01升高为7.06、SO24-由8.79 mg/L升高为11.40 mg/L、Cl-由10.54 mg/L升高为11.88 mg/L,这一结果表明,HCrO4-与铝污泥表面的羟基、SO24-、Cl-等官能团交换,其吸附机理为配体交换;(3)pH是影响Cr(Ⅵ)在铝污泥上的吸附量的主要因素,当pH由4.0升高至10.0时,吸附容量由7.63 mg/g下降为0.70 mg/g。实验表明,铝污泥作为一种新型的Cr(Ⅵ)吸附剂具有较高吸附能力和应用前景,并为优化吸附工艺提供了技术支撑。     

硝酸改性活性炭的制备及其对Cr（Ⅵ）

利用硝酸对颗粒活性炭进行改性,处理含铬废水,并考察了吸附时间、溶液pH、吸附剂加入量对改性活性炭吸附Cr（Ⅵ）效果的影响。实验结果表明：经过硝酸氧化改性的活性炭比表面积有所增加,官能团总量增加明显;吸附剂对Cr（Ⅵ）的去除率随振荡时间的增加而增加;对于质量浓度为10mg/L的100mLCr（Ⅵ）溶液,当溶液pH为中性,30%（体积分数）硝酸改性的颗粒活性炭的加入量为0.4g,其对Cr（Ⅵ）的最大去除率为98%。     

降解菌ZQ5与紫茉莉对芘污染土壤的联合修复

在温室盆栽条件下,通过单独种植紫茉莉、单独接种多环芳烃(PAHs)模式化合物芘的专性降解菌ZQ5和两者的联合修复的3种处理,对芘污染土壤的修复效果进行了研究。结果表明,经90 d修复后,植物-微生物联合修复可将人工污染土壤中的芘降解81.1%,将石油污染土壤中的芘降解50.3%,其修复效率明显高于其他2种处理,是紫茉莉修复的1.98倍,是降解菌ZQ5修复的1.39倍。ZQ5的不同接菌量对于修复60 d后的降解率影响不大。外源生物修复条件下,10～20 cm土壤的修复效率要高于5 cm土壤;自然降解条件下,5 cm土层降解率略高于其他土层。