稀贵萃余液高结晶臭葱石除砷研究

化学沉淀法处理含砷废水,产物沉砷渣通常不稳定,易导致砷泄露,对环境造成严重的危害。采用沉砷率高、固砷渣稳定的低温常压臭葱石(FeAsO₄·2H₂O)沉砷法进行除砷,并研究了初始pH、Fe/As摩尔比、Fe₂(SO₄)₃滴加速率对As、Fe去除率,FeAsO₄·2H₂O结晶度,形貌和浸出毒性的影响。结果表明：初始pH和Fe/As摩尔比的升高有利于沉砷率的提高,但会导致沉砷渣中FeAsO₄·2H₂O结晶度和含量下降。提高Fe₂(SO₄)₃滴加速率有利于反应效率,但不利于FeAsO₄·2H₂O的纯度。在初始pH为1.5,Fe/As摩尔比为1.5,Fe₂(SO₄)₃滴加速率为40 mL/h以及滴加时间为1.125 h的条件下,...     

臭葱石法沉砷及井下充填材料制备

针对常规化学沉淀法处理工业含砷废水后得到的含砷固废物稳定性差且无法有效处理的问题，采用臭葱石法处理含砷废水，并进行了以含砷固废物制备井下充填材料的研究。结果表明：在初始pH=2、铁砷摩尔比1.2、反应温度95 ℃、反应时间7 h的最佳条件下，砷的沉淀率为85.07%，所得沉淀物颜色为浅绿色，其中砷含量30.4%、铁含量22.7%，毒性浸出砷浓度为4.33 mg/L。在灰砂比1︰6、料浆浓度65%的最佳条件下，臭葱石的添加量为7%，充填体养护3天后的强度达到1.12 MPa，料浆坍落度约为25.3 cm，满足井下填充要求。充填体毒性浸出砷浓度为1.4 mg/L，满足排放标准。     

含砷物料资源化利用与无害化处置技术路线探讨

介绍了含砷物料的来源及目前国内外处理含砷物料的技术现状,指出臭葱石固砷法、石灰、水泥固砷法等主要方法存在需要填埋场地、运行成本高、含砷物料没有资源化等不足,含砷物料产品化是含砷物料无害化与资源化处理的新途径,也是含砷物料处理技术发展的必由之路。     

臭葱石矿化沉砷研究现状与展望

综述了当前含砷废水臭葱石沉砷工艺的发展现状与研究动态。臭葱石沉砷法因砷渣渣量小、性质稳定等特点被认为是理想的固砷产物。详细阐述了臭葱石沉砷原理、工艺优化与调控、砷渣物相定向调控等，并对该技术的发展趋势进行展望，为有色金属行业清洁高效除砷工艺选择提供参考借鉴。     

水热臭葱石固砷过程Na+和K+的影响

水热臭葱石沉砷体系中Na⁺、K⁺碱金属离子对沉砷渣物相组成影响显著,Fe(Ⅲ)与As(Ⅴ)共沉淀生成臭葱石(FeAsO₄·2H₂O)、次水合砷酸铁(FeAsO₄·0.75H₂O)砷铁共沉淀物,同时Fe(Ⅲ)还以黄钠铁矾(NaFe₃(SO₄)₂(OH)₆)、黄钾铁矾(KFe₃(SO₄)₂(OH)₆)、碱式硫酸铁(Fe(OH)SO₄)形态竞争析出,从而影响沉砷渣的稳定性。在Na₂SO₄-(K₂SO₄)-FeSO₄-H₃AsO₄-H₂O体系中研究了Na⁺、K⁺     

As（V）-Fe（II）体系臭葱石固砷研究

研究了在As（V）-Fe（II）体系中将废水中的砷转化为臭葱石的模拟过程。考察了As（III）氧化为As（V）中双氧水过量系数、氧化时间、氧化温度对氧化率的影响，以及臭葱石沉砷实验中Fe（II）氧化方式、初始pH、 Fe/As摩尔比对沉砷效果的影响。结果表明：适当提高双氧水过量系数、氧化时间和氧化温度，均有利于提高As（III）的氧化率；臭葱石沉砷实验中加快Fe（II）氧化有利于臭葱石晶体的生长，可以提高沉砷率和臭葱石质量；适当提高初始pH和Fe/As摩尔比有利于提高沉砷率，虽然臭葱石结晶质量有所降低，但臭葱石毒性仍较低。在双氧水过量系数为1.5、氧化时间为1 h、氧化温度为45 ℃条件下，以60 mL/h的速率滴加0.3%H2O2溶液氧化Fe（II），当初始pH为2.0、 Fe/As摩尔比为1.5时， As（III）平均氧化率可达97.67%，平均沉砷率高达95.57%，臭葱石稳定性高，浸出毒性平均为1.00 mg/L。     

固体含砷废料的稳定性及处理方法

由于砷及其化合物为剧毒物质，固体含砷废料的稳定性及处理方法对环境保护至关重要。本文介绍了固体含砷废料稳定性的测定技术，综述了三氧化二砷、砷酸钙、硫化砷、含砷水铁矿和臭葱石等各种固体含砷沉淀物的稳定性及处理方法的研究成果。     

砷酸铁化合物的溶解度和稳定性

从湿法冶金过程的溶液中水解沉淀而得的碱性砷酸铁,在一定的pH范围内很难溶解。随着Fe/As比增加,稳定性的范围(溶解度相似文献   

含砷酸性废水除砷工艺现状与展望

综述了当前含砷废水主要处理方法如石灰法、石灰-铁盐法、硫化法以及臭葱石法的运行现状和研究动态。通过详细分析含砷酸性废水除砷工艺研究现状，着重探讨了上述除砷技术的反应原理、除砷效果、工艺特点，并对含砷酸性废水未来处理技术的发展趋势及研究方向进行了展望，为有色金属行业清洁高效除砷工艺选择及改进提供参考借鉴。     

不合格白钨精矿的盐酸处理

<正> 不少企业产出一种磷、砷、硫等杂质含量较高的白钨精矿,其中砷呈硫化物(如雄黄、砷黄铁矿,占含砷总量的90%)和臭葱石(FeAsO_4·2H_2O);磷主要呈磷灰石存在。为使上述含杂质较高的白钨精矿达到合格产品标准,曾用盐酸进行过浸洗和分解试验,结果表明:     

Novel atmospheric scorodite synthesis by oxidation of ferrous sulfate solution. Part I

A new atmospheric scorodite synthesis process was investigated. A large size and good crystalline scorodite was precipitated at 95 °C even in a short time of 1 to 7 h when ferrous ions were oxidized by oxygen gas in the presence of As(V) ion with concentrations as high as 50 g/L As in sulfuric acid solution. The key point of the process is the ferrous state of iron in solution and the oxidation of ferrous ions during the scorodite precipitation. This scorodite has a particle size of 15 μm with approximately 10% moisture content (wet base) even under atmospheric conditions. The arsenic content was about 30% by mass. The results of the leach test are very desirable. The process can be applied to a primary smelter which produces copper, zinc, lead and other secondary materials.     

Kinetic investigation of sulfidizing annealing of scorodite in processing of refractory oxidized gold-containing ores

The results of kinetic studies on the removal of arsenic from scorodite using sulfidizing annealing are presented. The reaction order with respect to the reactant and the activation energy are established from the experimental data. The rate-determining step of the sulfidizing annealing process is determined. The main reactions that occur during the sulfidizing of arsenic in scorodite are proposed on the basis of the obtained results and confirmed by thermodynamic calculations and chemical analyses. The major results of testing this technology, as applied to the refractory oxidized ores in which arsenic is mainly concentrated in scorodite, are presented. Arsenic removal from this ore is confirmed by chemical and quantitative X-ray diffraction analyses and by qualitative phase analysis. Industrial use of this technology provides safe and efficient processing of refractory gold-containing ores, where arsenic is mainly concentrated in scorodite.     

Effect of pH on atmospheric scorodite synthesis by oxidation of ferrous ions: Physical properties and stability of the scorodite

In the scorodite novel synthesis reaction, where ferrous ions were oxidized by oxygen gas in the presence of a high concentration of arsenic(V), the effect of sodium ion and reaction pH was investigated. The results indicate a prominent pH effect but a relatively minor influence of sodium ion. The pH range suitable for the synthesis of stable scorodite was pH 0.3 to 1.0. For solution pH higher than 1.2, the precipitates were very fine and the amounts of scorodite and arsenic that dissolved increased. The leaching profile showed a striking change at pH 1.2 that has not been adequately explained by previous literature.     

Novel atmospheric scorodite synthesis by oxidation of ferrous sulfate solution. Part II. Effect of temperature and air

We have previously reported a novel method for producing stable scorodite (FeAsO₄·2H₂O) under atmospheric conditions in which ferrous sulfate was oxidized by oxygen in the presence of high concentrations of arsenic(V). This work examines the effects of reaction temperature (95, 70, 50 °C) and the oxidizing agent (air, pure oxygen gas) to optimize scorodite formation in a practical process. Crystalline scorodite of low solubility could be prepared at 70 °C within only 7 h using either oxygen or air sparging and small particles were even formed at 50 °C using air oxidation.     

Aqueous precipitation and crystallization for the production of particulate solids with desired properties

It is the scope of this paper to review and apply the theory of crystallization kinetics to the analysis and design of aqueous inorganic hydrometallurgical precipitation systems. In particular the critical role of supersaturation in controlling the properties (crystallinity–stability, particle size and cleanliness) of the precipitated compounds is emphasized. The approach taken is of generic nature and not system-specific; however, reference is made to particular precipitation systems such as production of very fine monodispersed particles, hydrolysis/neutralization of acidic ferric sulphate liquors, iron precipitation from zinc process solutions, immobilization of arsenic in the form of crystalline scorodite, and gypsum crystallization in waste water treatment. Reference to these systems is not made with the purpose of describing the respective processes but rather to reinforce the validity of the supersaturation-controlled approach to industrial inorganic precipitation processes.     

饮用水中砷处理技术的研究进展

简单介绍了饮用水中砷的来源及危害,重点阐述了发展较为成熟的饮用水除砷技术,包括：混凝／沉淀法、吸附法、离子交换法、膜技术以及生物技术,通过分析比较可知,各种技术各具优缺点,混凝沉淀法和吸附法已被广泛应用;对环境条件要求较高的离子交换法和膜技术发展受到限制;生物技术具有良好的环境效益,应用前景广阔．最后对我国饮用水除砷技术的发展方向进行了展望,指出从我国基本国情考虑,混凝吸附为主的小型除砷装置占优势;从长远角度考虑,离子交换法和膜技术最具应用前景;从环境保护的角度看,生物技术高效廉价,必将引来更多的关注和研究．     

The incongruent dissolution of scorodite — Solubility,kinetics and mechanism

This work reports the results of a laboratory investigation on the long-term stability of crystalline scorodite conducted at fixed pH (5–9) and temperature (22 °C, 50 °C and 75 °C). The scorodite used in this work was prepared via a hydrothermal synthesis procedure. The dissolution of scorodite at 22 °C was found to be extremely slow. At neutral pH, the arsenic concentration stabilized after 24 weeks at 5.9 mg/L. Analysis of the solubility data as a function of temperature yielded a scorodite solubility model equation. The solubility product of scorodite was recalculated as 10^− 25.4 using the solubility data generated by the study and the geochemical code PHREEQC for solution modelling. As scorodite dissolved, the iron re-precipitated as 2-line ferrihydrite. The growth and re-crystallization of ferrihydrite was apparently retarded by arsenate adsorption. The dissolution rate of scorodite was modeled with a decreasing exponential equation. The initial rate approached first order dependency on OH⁻ concentration while the apparent activation energy suggested that scorodite dissolution is chemically controlled.     

Acidity, valency and third-ion effects on the precipitation of scorodite from mixed sulfate solutions under atmospheric-pressure conditions

The present study is focused on the precipitation of scorodite from mixed sulfate media at 95 °C under atmospheric pressure. In particular, this study explores the effects of acidity (pH), valency [Fe(II)/Fe(III), As(III)/As(V)], and solution composition (third cation/anion) on the yield, crystallinity, and stability (leachability) of scorodite precipitates. Thus, it was found that the precipitation of crystalline scorodite can be achieved without stringent pH control once the precipitation has started. Nonetheless, the selection of the initial pH is critical to avoid the formation of an amorphous precipitate. A leachability as low as 0.5 mg/L As at pH 5 and 22 °C (TCLP-like test) is obtained when the initial molar ratio Fe(III):As(V) is increased to 3:1, but the precipitation yield is very low. When Fe(II) is used as excess iron, the precipitate solubility drops to 0.2 mg/L As with a yield exceeding 80 pct in 2.5 hours. The stability of the product is not measurably affected by the presence of Cu²⁺, Zn²⁺, Ni²⁺, Co²⁺, Mn²⁺, SO ₄ ²⁻ , and NO ₃ ⁻ . The presence of PO ₄ ³⁻ , however, leads to the formation of crystalline phosphate-containing scorodite precipitates of somewhat reduced stability. In most cases, the TCLP leachability of the precipitate was found to be between 1 and 3 mg/L As, and never exceeded the regulatory limit of 5 mg/L As.     

Temperature and seeding effects on the precipitation of scorodite from sulfate solutions under atmospheric-pressure conditions

Arsenic is a major contaminant in the nonferrous extractive metallurgy. In the past 20 years, many studies have shown that it can be precipitated as relatively stable crystalline scorodite (FeAsO₄·2H₂O) by precipitation under ambient or elevated pressures. In the present study, an extensive program of scorodite precipitation tests under ambient pressure has shown that the rate of scorodite formation increases dramatically by a small increase in temperature from 85 °C to 100 °C. The beneficial effects of temperature are attributed to the higher thermodynamic stability of scorodite at elevated temperatures, but also to higher rates of secondary nuclei formation and crystal growth. In any case, irrespective of the precipitation temperature, the leachability of all scorodite precipitates observed in toxicity characterization leaching procedure (TCLP) tests is below 5 mg/L As. Another parameter examined in this study was seeding. It was observed that the higher the initial concentration of seed, the faster the precipitation. Precipitation of well-crystallized scorodite can be effected equally well on heterogeneous seed such as hematite (Fe₂O₃) or gypsum (CaSO₄·2H₂O) added externally or formed in situ.