降低选矿厂废水控制和净化费用的途径

选矿厂和黄金回收工厂的废水主要是被氰化物、硫氰酸盐、有色金属离子、黄原酸盐、硫化物、起泡剂和某些其他物质所污染。根据研究,在多金属选矿厂废水净化和调节的复杂条件下,确定了上述组分浓度之间相互关系。这使得有可能对废水每一组分的毒性进行控制,控制氰化物和硫氰酸盐的总含量,其中氰化物和硫氰酸盐基本上与铜和锌结合成络合物。废水中这些组分的浓度经常波动,导致对它需要连续不断地进行自动控制。为此,     

焦化废水中主要五种无机态氮含量与总氮含量的关系

阐述了分析氨氮、硝酸盐氮、亚硝酸盐氮、氰化物!包括易释放氰和络合氰"、硫氰酸盐等五种无机态氮和总氮的分析方法,并对焦化废水中五种无机态氮与总氮进行了分析。实验 结果表明,氨氮、硝酸盐氮、亚硝酸盐氮和硫氰酸盐四种物质是焦化废水中总氮的主要来源;氨氮、亚硝酸盐氮在分析过程中转化成总氮的效率大于95%,而硫氰酸盐和络合氰的转化效率只有88%和75%。焦化废水中总氮的分析结果小于这五种无机态氮分析结果的总和$总氮的分析效率约为83%···101%。     

国外信息

生物转盘技术处理矿业废水中的氰化物、硫氰酸盐和氨在加拿大和非洲,对尾矿坝废水进行处理的半工业性生产实践显示:生物转盘工艺(Rotating Biological Contactor:RBC;采用生物膜法处理废水的一种装置)能够经济、有效地处理矿山生产所产生的废水。在北美,作为生物转盘工艺技术的     

极高浓度含氰废水综合回收治理技术研究

针对某黄金冶炼厂极高浓度含氰废水中污染物的组分分析结果,采用酸化法及OOT或GOC清洁药剂联合工艺对其中的氰化物、硫氰酸盐及铜进行了酸化、氧化和回收利用;同时,对药剂成本、动力成本及经济效益进行了核算。其治理工艺试验结果表明,利用酸化法及清洁药剂氧化联合工艺对极高浓度含氰废水进行深度治理后,回收利用及治理效果均很好,无二次污染,且经济效益、环境效益显著。     

SO_2/Air法—化学沉淀法联合处理氰化浸金废水

某金矿氰化浸金尾矿浆采用SO_2/Air法处理,高质量浓度硫氰酸盐的存在导致处理后废水中总氰化合物质量浓度偏高。采用SO_2/Air法—化学沉淀法联合处理氰化浸金废水,考察硝酸锌沉淀法和硫酸亚铁沉淀法的处理效果。试验结果表明:2种化学沉淀法处理后废水中总氰化合物、砷质量浓度分别低于0.3 mg/L和0.1 mg/L,符合国家废水排放标准,但硫酸亚铁沉淀法处理成本低,经济性好,更适用于工业生产。     

黄金行业特征废水中BOD测定影响因素的分析

黄金行业特征废水通常含重金属、氰化物及硫氰酸盐,且具有强碱性,研究好氧自养型微生物、无机盐、溶解氧含量、接种液背景BOD值及废水性质等5个因素对BOD测定结果的影响。研究结果表明,黄金行业特征废水BOD测定需添加丙烯基硫脲抑制硝化细菌,加入微生物生命活动所需的无机盐,保证水样中溶解氧含量饱和或接近饱和,接种液背景BOD值低,选择耐氰耐重金属的微生物进行接种或根据废水性质对接种液中微生物进行驯化后接种,满足以上条件才能保证BOD测定结果准确。     

生物氧化预处理工艺在卡林型金矿的应用实践

针对卡林型金矿石含砷、含汞,硫含量低,金主要以包裹金形式嵌存于硫化矿物中等性质,锦丰矿业公司采用生物氧化工艺对其浮选金精矿进行预处理。经过近10年的生产运行表明,生物氧化工艺能有效处理卡林型金矿石,金回收率等技术指标均达到并超过设计水平,取得了良好的经济效益和社会效益。在运行过程中,根据现场生产情况对各项工艺参数进行不断优化及流程改造等,金炭浸回收率提高至93%左右。炭浸后废水采用INCO法和A/O法处理氰化物和硫氰酸盐,出水水质达到国家废水排放标准。     

黄金氰化浸取液中硫氰酸根的测定

从黄铁矿废渣中回收金银,因渣中残硫的存在,在氰化处理过程中,部份残硫转化成硫氰酸盐。钝化了部份氰根对金银的氰化作用,因而硫氰酸盐的转化率为黄金冶炼所 重视。 目前氰化过程中硫氰酸盐的测定方法,文献报导甚少。本方法对氰化过程中贵液贫液中硫氰酸根离子测定,进行了一系列试验     

秘鲁Minacalpa含硫氰酸盐的难处理金矿尾渣的生物氧化

金采矿生产中的难处理、硫化物尾渣可以通过生物氧化提高金的氰化提取率。含有硫氰酸盐的尾渣要进行预处理,在生物氧化之前去除硫氰酸盐,因为硫氰酸盐对氧化硫化矿物的微生物具有毒性。秘鲁Minacalpa尾渣中的硫氰酸盐用水或稀硫酸仅可部分去除。在自然pH条件下,硫氰酸盐也不能完全得到生物降解。经过预处理,抑制生物氧化的残留尾渣将硫氰酸盐释放到浸出液中。Minacalpa尾     

钢铁企业焦化废水的深度处理

焦化废水是钢铁企业排出的主要废水之一。焦化废水是煤在高温干馏过程中形成的废水,其中含有酚、氨氮、氰、苯、吡啶、吲哚和喹啉等几十种污染物,成分复杂,污染物浓度高、色度高、毒性大,性质非常稳定,是一种典型的难降解有机废水。它的超标排放对人类、水产、农作物都构成了很大危害。如何改善和解决焦化废水对环境的污染问题,已成为钢铁行业的一个重大任务。     

尾矿库氰渣淋溶废水深度处理工艺研究

针对黄金矿山尾矿库氰渣淋溶的低质量浓度含氰废水,采用OOT/OCT—BAF联合工艺进行处理。其试验结果表明,在进水总氰化合物为64.45 mg/L、硫氰酸盐为22.74 mg/L、COD为76.58 mg/L、铜为72.48 mg/L的条件下,当臭氧投加量为250 mg/L、臭氧投加量分流比为2∶1、BAF的废水停留时间为20 min、气水比为3∶1时,出水总氰化合物为0.02 mg/L、硫氰酸盐完全去除、COD为5.43 mg/L、铜为0.32 mg/L、氨氮为0.79 mg/L,出水达到《GB 3838—2002地表水环境质量标准》Ⅲ类水质。     

Biooxidation of thiocyanate-containing refractory gold tailings from Minacalpa,Peru

Refractory, sulfidic tailings from gold mining operations may be biooxidized to increase the amount of gold recoverable by cyanide extraction. Tailings containing thiocyanate must be pretreated to remove thiocyanate prior to biooxidation due to its toxicity to microorganisms that oxidize sulfide minerals. Thiocyanate in tailings at Minacalpa, Peru, was only partially extractable with water or with dilute sulfuric acid. The thiocyanate also was not completely biodegradable at neutral pH. Consequently, tailings remained inhibitory toward biooxidation after these treatments, releasing thiocyanate into bioleach solutions. The non-extractable form of thiocyanate in Minacalpa tailings was probably copper thiocyanate. A novel approach was developed to remove this thiocyanate using ferric sulfate solution. Tailings were detoxified by washing with either reagent ferric sulfate or solutions derived from biooxidation of pyrite. Detoxified tailings, i.e., those thoroughly washed with ferric sulfate solution, were biooxidized, exhibiting a fairly linear relationship between sulfide-S oxidation and cyanide gold recovery. A process for biooxidation of Minacalpa tailings would involve an initial washing step with biooxidation solutions followed by stirred tank biooxidation or agglomeration of detoxified tailings onto support rock and biooxidation in heaps.     

The effects of different (pseudo)halide substrates on peroxidase-mediated killing of Actinobacillus actinomycetemcomitans

Actinobacillus actinomycetemcomitans is a Gram-negative bacterium which has an important role in localized juvenile and in progressive periodontitis. It is sensitive to killing by the myeloperoxidase (MP)-hydrogen peroxide (H2O2)-chloride system which is part of the innate host defense mediated by polymorphonuclear leukocytes. Since it has been recently suggested that thiocyanate, instead of chloride, could serve as a main substrate for MP as for lactoperoxidase (LP) and salivary peroxidase, we investigated in this study the effect of both LP and MP systems on A. actinomycetemcomitans with different (pseudo)halide substrates, thiocyanate, chloride and iodide. The concentrations of the substrates were physiological for oral fluids, as was the concentration range of H2O2. Both peroxidases produced end products with identical antibacterial activity with thiocyanate and iodide. The oxidation of iodide resulted in the highest antimicrobial efficiency followed by chloride and thiocyanate. Addition of thiocyanate into either MP-H2O2-chloride or MP/LP-H2O2-iodide system abolished the bactericidal activity of the oxidized halide. However, the chloride did not affect the bactericidality of the MP-H2O2-iodide system, but when all 3 (pseudo)halide substrates were present no antimicrobial effect was recorded. Our study shows that the presence of thiocyanate in physiological amounts is able to prevent the bactericidal activity of halide-peroxidase systems in low H2O2 concentrations. These results explain why thiocyanate-peroxidase systems of either innate origin (saliva, crevicular fluid) or introduced by commercial oral hygiene products are most probably ineffective against A. actinomycetemcomitans in vivo. Further studies of halide/thiocyanate ratio are needed to develop products which are also effective against oral anaerobes.     

Characterization of the interaction between bovine pancreatic trypsin inhibitor and thiocyanate by NMR

The interaction between Bovine Pancreatic Trypsin Inhibitor and thiocyanate was studied using NMR spectroscopy following several experimental approaches. The chemical shift variations of the BPTI protons in the absence and in the presence of increasing thiocyanate concentrations (up to 0.2 M) were significant (> 0.05 ppm) for 30 protein protons belonging to 20 residues. The largest deviation, 0.2 ppm, was observed for the amide backbone proton of Arg42 in the absence of thiocyanate and in the presence of 40 molar equivalents of thiocyanate. The influence of the presence of thiocyanate on the electrostatic potential surrounding the protein was demonstrated by NOESY spectra selective at the water frequency: the presence of SCN- favours acid catalysed exchange and disfavours base catalysis. However, a specific effect of thiocyanate was pointed out since the comparison of the chemical shifts in the presence of 40 molar equivalents of KSCN and KCl, respectively, showed much more as well as larger deviations compared to measurements in the absence of salt. A dissociation constant, KD, for a 1/1 complex between BPTI and thiocyanate was calculated from chemical shifts measurements: KD = 89 +/- 8 mM. A second value, KD = 99 +/- 10 mM, was extracted from SC15N relaxation time measurements.     

Dietary deficiency of cystine and methionine in rats alters thiol homeostasis required for cyanide detoxification

Nutritional status is an important factor in modulating the metabolic fate of xenobiotics. Sulfur amino acid (SAA) deficiency has been proposed as a risk factor for human neurological diseases among protein-poor populations subsisting on the cyanophoric plant cassava. Female Sprague-Dawley rats were used to develop and define a model of SAA deficiency for use in future studies examining cassava-related neurotoxicity. Rats were kept in metabolic cages for 7-21 d and fed a balanced diet (BD) of known composition or a comparable diet selectively deficient in methionine and cystine (SAA-free diet). Animals fed the SAA-free diet failed to thrive, lost body weight, excreted porphyrinic materials, and showed a steep and persistent reduction of urinary inorganic sulfate. In contrast, animals on the BD gained body weight and maintained baseline output of urinary inorganic sulfate. Urinary thiocyanate excretion did not differ between groups, but plasma thiocyanate concentrations reached double that in SAA-deficient rats. Increased plasma thiocyanate suggests mobilization of sulfur amino acids from endogenous sources. Liver glutathione and blood cyanide concentrations were similar in animals on the BD and the SAA-deficient diet. In summary, a diet free of methionine and cystine results in increased retention of inorganic sulfur as thiocyanate and a near absence of inorganic sulfur excretion in urine.     

金矿含氰污水微生物处理的理论与实践

微生物处理含氰污水是国内外正在探索的新技术．研究表明，微生物对污水中氰化物、硫氰酸盐、多种金属离子有脱除能力，并将氰化物、硫氰酸盐分解为CO2，NH3和硫酸盐，达到无毒排放．结合作者探索性研究的初步成果，综合论述了可用于处理含氰污水的微生物种属及其生化作用，介绍了国外的工业实践现状，微生物处理金矿含氰污水具有广阔应用前景．     

Multiple sclerosis and the neurogenic bladder

Allosteric regulators of alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionate (AMPA) receptors include 2,3-benzodiazepines such as GYKI 52466 and GYKI 53655 and the chaotropic anion thiocyanate that inhibit, and benzothiadiazines such as cyclothiazide that potentiate AMPA receptor currents. Here we sought to determine whether the allosteric regulators modulate AMPA receptors at a common or distinct allosteric sites by comparing their actions on AMPA- and kainate-evoked currents in cultured rat hippocampal neurons and Xenopus oocytes expressing recombinant AMPA receptor subunits. GYKI 52466 and thiocyanate blocked AMPA-evoked currents in a concentration-dependent manner (IC50 values, 8.2 microM and 1.1 mM, respectively); in contrast, kainate-evoked currents were blocked by GYKI 52466, but were potentiated by high concentrations of thiocyanate (> or = 3 mM). Thiocyanate enhanced the rate of desensitization and slowed recovery from desensitization of AMPA-evoked currents, whereas GYKI 52466 failed to affect desensitization. Among neurons in the hippocampal cultures, there was cell-to-cell variability in the sensitivity to block of AMPA-evoked currents by thiocyanate that was correlated with the degree of potentiation by cyclothiazide. Moreover, cyclothiazide caused a parallel rightward shift in the concentration-response curve for thiocyanate block, and slowed the onset of thiocyanate block to a rate that was similar to that of cyclothiazide dissociation. Together, these observations suggest that thiocyanate and cyclothiazide act at non-distinct allosteric sites. GYKI 52466 blocked AMPA receptor responses to a similar extent, irrespective of the degree of cyclothiazide potentiation. Moreover, the kinetics of GYKI 53655 block in the presence of cyclothiazide were not consistent with a competitive interaction. As is the case for cyclothiazide, SCN- exhibited greater affinity for flip than for flop AMPA receptor splice variants. In particular, GluR1flip/GluR2flip was especially sensitive to thiocyanate block. We conclude that thiocyanate, a flip-preferring allosteric modulator like cyclothiazide, appears to act by enhancing desensitization at a site that may overlap the site where cyclothiazide reduces desensitization, whereas 2,3-benzodiazepines act at a distinct site and the block does not involve a modification of desensitization.     

Electrooxidation of thiocyanate on the copper-modified gold electrode and its amperometric determination by ion chromatography

Cyclic voltammetry was used to investigate the electrochemical behavior of an Au/Cu electrode towards the electrooxidation of thiocyanate ion in alkaline medium. The effects of pH, copper loading, scan rate and applied potential on the electrocatalytic oxidation of thiocyanate have been investigated. Flow injection experiments and ion-chromatography (IC) were performed to characterise the electrode as an amperometric sensor for the thiocyanate determination. The effects of carbonate concentration and common interferents on the retention time were also estimated. The electrode stability, precision, limit of detection and linear range were evaluated at a constant applied potential of 0.7 V vs. Ag/AgCl. Calibration plots, obtained in IC, were linear from 1.0 to 195 microM (correlation coefficient of 0.9984). The detection limit (LOD) was 0.5 microM (29 ppb) in a 50 microlitres injection. An example of analytical application, which includes the IC separation and detection of thiocyanate ion present in human urine, is given.     

Separation of platinum and palladium from chloride solution by solvent extraction using Alamine 300

The separation of platinum and palladium from chloride solution by solvent extraction, using Alamine 300 as an extractant, has been studied. The effect of different parameters such as the concentration of HCl in the feed solution, NaCl concentration, extractant concentration, and platinum and palladium concentrations in the feed solution has been evaluated. Stripping behavior was also studied using different stripping agents, such as sodium thiocyanate and thiourea. Using a saturated solution of sodium chloride at a pH 1.5, platinum was selectively extracted as the major component, along with minor amounts of palladium. By adding a saturated solution of NaCl to the aqueous phase, palladium extraction could be decreased. Additionally, with the use of 0.5 M HCl in place of NaCl, both metals were studied. Selective stripping of platinum accomplished using sodium thiocyanate, and the selective removal palladium was achieved with sodium thiosulfate. This process can achieve a 99.9% purity of platinum even in very dilute solution.