有色金属冶炼中含砷物料的除砷技术研究现状

综述了砷对冶金、环境以及人类的危害,阐述了冶金工业中含砷物料的除砷技术的发展现状,介绍了各种技术的原理、应用,分析了各种技术的优缺点,展望了除砷技术的发展方向。     

含砷工业废水处理现状与进展

介绍了用沉淀法、离子交换法、吸附法、萃取法、电凝聚法、膜分离技术、浮选法、生物技术、光催化氧化法处理含砷废水的原理、优缺点以及适用范围,并提出了开发新型吸附材料、新型除砷技术、稳定沉淀技术和多种除砷技术联用的展望.     

铁基水处理材料除砷技术的研究进展

自然环境中的砷污染问题被认为是全球最严重的环境威胁之一,人类长期暴露于含砷饮用水环境中会引起各种疾病的发生,因此,开发经济有效的除砷技术一直是砷污染治理领域的研究热点。铁基水处理材料由于其对砷的良好亲和力、表面反应活性强、价廉易制、便于回收等特点,一直备受关注。本文综述了近年来不同铁基水处理材料如铁(氢)氧化物、纳米零价铁、铁基多金属氧化物复合材料除砷技术的研究进展,论述了铁基水处理材料对水相中砷去除的影响因素及机理;同时,对影响铁基水处理材料砷解吸的因素和毒性评估研究进行了总结;指出了目前铁基水处理材料砷污染去除技术研究中存在的主要问题,并对水相砷污染去除技术研究中值得关注的重要发展方向进行了展望。     

含砷钢铁中磷砷的吸光光度法联合测定

本法利用磷钼蓝与砷钼蓝吸光度具有加和性的特点,首先利用高酸度提高五价砷的氧化电位,以亚硫酸钠－硫代硫酸钠（双硫）为As(V)及Fe(Ⅲ）的复合还原剂^[1-3],溴化物为还原As(Ⅴ)的动力催化剂^[4],使As(Ⅴ)还原至As(Ⅲ),彻底消除砷的干扰,可测定磷的吸光度^[6],然后,在一般条件测定磷＋砷的吸光度,差量法求得砷的吸光度,最后分别从磷有砷的工作曲线上查出磷和砷的含量。     

含铁有色金属矿渣的除砷方法

用ICP-AES法初步研究了含铁的有色金属矿渣除砷的方法.采用以硝酸为主的低浓度浸取液,在不损失铁含量的前提下,除砷效果好,且成本较低、周期短、工艺简单.     

碘量法测定复杂含硒物料中常量硒

用碘量法测定复杂含硒物料中常量硒并对测定条件做试验。试样经硝酸及硫酸溶解、蒸发至冒烟后,盐类溶于盐酸中。在酒石酸存在下加盐酸羟胺,于70℃保温1h,放置1.5h使硒还原为单质硒并陈化。过滤,将单质硒溶于盐酸中,溶解温度为90℃,溶解时间为5min,滴定时溶液酸度宜在0.2~0.5mol·L-1(盐酸介质)。滴定时采用分步滴加碘化钾溶液,随即用硫代硫酸钠标准溶液滴定至淀粉指示剂所显蓝色消失,至再次加入碘化钾无蓝色出现为终点。按所耗硫代硫酸钠标准溶液的体积计算试样的含硒量。     

蒸馏-催化极谱法测定复杂物料中微量砷

提出了用催化极谱法测定复杂物料中微量砷的含量。选择测定的溶液介质中含碲(Ⅳ)硫酸溶液5mL和150g.L-1碘化钾溶液5mL。仪器扫描速率为250mV.s-1,并采用二阶导数测定。试样(0.01～1.0g)用氯酸钾0.5g、氢氟酸5滴、硝酸5～10mL溶解,用蒸馏法分离其中的砷。砷的质量浓度在0.4mg·L-1以内与相应的峰电流呈线性关系。按此方法测定了12个矿样中砷含量,其测定值与已知值相符。方法的回收率在97%～100%之间,相对标准偏差(n=6)在2.3%～7.2%之间。     

返滴定法测定含镍锌物料中的锌含量

使用盐酸-硝酸-硫酸将试样溶解,并在氨性条件下过滤,沉淀分离大量共存元素,加入掩蔽剂掩蔽滤液中的干扰元素,在pH=5.5～6.0的缓冲溶液中,选用二甲酚橙作为指示剂,加入过量的EDTA标准滴定溶液,静置使之与溶液中的镍、锌等金属离子充分络合,用氯化锌标准滴定溶液滴定过量的EDTA。测得结果为锌、镉、镍合量,扣除镉、镍量,即为锌量。用来测定含镍锌物料中的锌,其结果的相对标准偏差(RSD,n=11)为0.21%～0.87%,加标回收率为99.0%～102%,满足日常检测需求。     

溴酸钾滴定法测定铜冶炼烟尘中的砷含量

研究了测定铜冶炼烟尘中砷含量的溴酸钾滴定方法。对测定体系中的各共存元素进行研究,探讨了测定方法的各项测定条件,方法的相对标准偏差RSD为0.13%～0.61%,样品加标回收率在99.5%～100%,方法精密度高,准确度好,适用于铜冶炼烟尘中砷含量为1.00%～50.00%的测定。     

硼酸盐润滑油添加剂的研究现状和进展

综述了国内外硼酸盐润滑油添加剂的研究现状,介绍了针对其合成和作用机制研究的进展,并对其前景进行了展望.指出硼酸盐已成为近年来绿色润滑油添加剂研究领域的热点之一,有机硼酸盐润滑油添加剂克服了无机硼酸盐分散稳定性差的弱点,代表了综合性能优良的硼酸盐润滑油添加剂的发展方向.     

The analytical use of neutrons in the non-ferrous metal industry

Activation analysis with reactor neutrons is used as a complement to the chemical methods for the fabrication of standard materials or for the determination of rraces in non-ferrous metals. The 14 MeV neutrons are used to determine oxygen in metals. Finally, certain problems such as the determination of F in salts, Si in Al−Si alloys or B in the AT5B alloy can be solved by using the neutrons from an isotopic source.     

The methylation of arsenic in marine sediments

Laboratory studies have shown that microorganisms present in both natural marine sediments and sediments contaminated with mine-tailings are capable of methylating arsenic under aerobic and anaerobic conditions. Incubation of sediments with culture media produced volatile arsines [including AsH₃, (CH₃)AsH₂, and (CH₃)₃As] as well as the methylarsenic(V) compounds (CH₃)_nAs(O) (OH)_3?n (n = 1, 2, 3). The concentration of the arsines increased and then decreased in a growth and decay pattern reminiscent of the methylation and demethylation of mercury. Thus, arsenic speciation varied with time, being controlled by the biochemical activity of the dominant microbe(s) at the time of sampling, and changing in response to the ecological succession within the microbial community. The analysis of the interstitial waters of sediments collected from several British Columbia (Canada) coastal sites gave results that were consistent with the culture experiments, in that the methylarsenicals were ubiquitous, but present only in small amounts. It is estimated that methylarsenic(V) species account for less than 1% of the arsenic present in porewaters. The actual proportion was dependent on a number of factors but, contrary to prevailing viewpoints, there was no relationship to the organic content of the sediments, nor did methylation occur only in the presence of high arsenic concentrations. Instead, all of the evidence was consistent with in situ microbial methylation and demethylation processes that are similar to the arsenic transformations that occur in soil ecosystems. The results are discussed in terms of the cycling of arsenic in the marine environment and within the marine food web.     

Distribution of arsenic species in the freshwater crustacean Procambarus clarkii

The concentrations of total arsenic and arsenic species in the complete organism of the crayfish Procambarus clarkii and its various parts (hepatopancreas, tail, and remaining parts) were analyzed in order to discover the distribution of arsenic and its species. With this information it will be possible to establish where the chemical forms of this metalloid tend to accumulate and what risks may derive from the contents and species present in the edible parts of this crustacean. The total arsenic content in the complete organism and in the various parts analyzed ranged from 2.5 to 12 µg g^?1 dry mass (DM), with inorganic arsenic representing 18 to 34% of total arsenic. The arsenical composition varied according to the part of the crayfish considered. The hepatopancreas had the highest levels of total arsenic (9.2–12 µg g^?1 DM) and inorganic arsenic (2.7–3.2 µg g^?1 DM). The tail (edible part) had the lowest levels of both total arsenic (2.5–2.6 µg g^?1 DM) and inorganic arsenic (0.46–0.64 µg g^?1 DM). The predominant organoarsenical species were the dimethylarsinoylribosides: glycerol riboside in the hepatopancreas, sulfate riboside in the tail, and sulfonate and phosphate ribosides in the remaining parts. Copyright © 2002 John Wiley & Sons, Ltd.     

Spectrophotometric determination of iron in aluminium metal and some non-ferrous alloys

A new, sensitive and selective spectrophotometric method is suggested for the determination of traces of iron(III) based on complex formation with hematoxylin in presence of cetyltrimethylammonium bromide (CTAB). Addition of CTAB shifted the absorption maximum of the iron-hematoxylin complex from 630 to 640 nm and increased its molar absorptivity from 9.88 × 10⁴ to 1.16 × 10⁵ 1·mol^–1·cm^–1. The method adhered to Beer's law up to 0.4 and 0.2 g/ml of iron in presence and absence of CTAB, respectively. The corresponding values of Sandell's sensitivity were 0.5 and 0.6 ng·cm^–2. The effect of reagent and surfactant concentrations, pH and standing time were investigated. EDTA, tartrate and sodium fluoride were used as masking agents for most of the interfering ions. The method was successfully used for the determination of iron in aluminium metal and some non-ferrous alloys.     

Distribution and cycle of arsenic compounds in the ocean

In order to understand the distribution and the cycle of arsenic compounds in the marine environment, the horizontal distributions of arsenic(V) [As(V)], arsenic(III) [As(III)], monomethylarsonic acid (MMAA) and dimethylarsinic acid (DMAA) in the Indian Pacific Oceanic surface waters have been investigated. This took place during cruises of the boat Shirase from Tokyo to the Syowa Station (15 November–19 December 1990), of the tanker Japan Violet from Sakai to Fujayrah (28 July–17 August 1991) and of the boat Hakuho-maru from Tokyo to Auckland (19 September–27 October 1992). Vertical distributions of arsenic in the west Pacific Ocean have also been investigated. The concentration of As(V) was found to be relatively higher in the Antarctic than in the other areas. Its concentration varied from 340 ng dm^?3 (China Sea) to 1045 ng dm^?3 (Antarctic). On the other hand, the concentrations of the biologically produced species, MMAA and DMAA, were extremely low in the Antarctic and southwest Pacific waters. Their concentrations in Antarctic waters were 8 ng dm^?3 and 22 ng dm^?3 and those in the southwest Pacific were 12 ng dm^?3 and 25 ng dm^?3. In the other regions the concentration varied from 16 ng dm^?3 (China Sea) to 36 ng dm^?3 (north Indian Ocean) for MMAA and from 50 ng dm^?3 (east Indian Ocean) to 172 ng dm^?3 (north Indian Ocean) for DMAA. As a result, with the exception of Antarctic and southwest Pacific waters, the percentages of each arsenic species in the surface waters were very similar and varied from 52% (east Indian Ocean) to 63% (northwest Pacific Ocean) for As(V), from 22% (northwest Pacific Ocean) to 27% (east Indian Ocean) for As(III) and from 15% (northwest Pacific Ocean) to 21% (north and east Indian Oceans) for the methylated arsenics (MMAA+DMAA). These percentages in Antarctic waters were 97%, 0.2% and 2.8%, respectively, and those in the southwest Pacific Ocean were 97% for As(V)+As(III) and 3% for MMAA+DMAA. The very low concentrations of the biologically produced species in Antarctic waters and that of methylated arsenic in southwest Pacific waters indicated that the microorganism communities in these oceans was dominated by microorganisms having a low affinity towards arsenic. Furthermore, microorganism activity in the Antarctic was also limited due to the much lower temperature of the seawater there. The vertical profile of inorganic arsenic was 1350 ng dm^?3 in surface waters, 1500 ng dm^?3 in bottom waters with a maximum value of 1700 ng dm^?3 at a depth of about 2000 m in west Pacific waters. This fact suggested the uptake of arsenic by microorganisms in the surface waters and the co-precipitation of arsenic with hydrated heavy-metal oxides in bottom waters. The suggested uptake of inorganic arsenic and subsequent methylation was also supported by the profile of DMAA, with a high concentration of about 26 ng dm^?3 in surface water and a significant decrease to a value of 9 ng dm^?3 at a depth of 1000 m.     

The discovery of hidden arsenic species in coastal waters

The analysis of ultraviolet (UV)-irradiated and untreated seawater samples has shown that the dissolved arsenic content of marine waters cannot be completely determined by hydride generation–atomic absorption spectrophotometry without sample pretreatment. Irradiation of water samples obtained during a survey of arsenic species in coastal waters during the summer of 1988 gave large increases in the measured speciation. Average increases in the measured speciation. Average increases in total arsenic, monomethylarsenic and dimethylarsenic were 0.29 μg As dm^?3 (25%), 0.03 μg As dm^?3 (47%) and 0.12 μg As dm^?3 (79%), respectively. Overall, an average 25% increase in the concentration of dissolved arsenic was observed following irradiation. This additional arsenic may be derived from compounds related to algal arsenosugars or to their breakdown products. These do not readily yield volatile hydrides when treated with borohydride and are not therefore detected by the normal hydride generation technique. This has important repercussions as for many years this procedure, and other analytical procedures which are equally unlikely to respond to such compounds, have been accepted as giving a true representation of the dissolved arsenic speciation in estuarine and coastal waters. A gross underestimate may therefore have been made of biological involvement in arsenic cycling in the aquatic environment.