基于响应曲面法的桑叶萃余物多糖提取工艺优化

以提取生物碱和黄酮的桑叶萃余物为原料,采用响应曲面分析法(RSM)优化桑叶萃余物多糖的超声提取工艺。在单因素实验的基础上,选取对实验结果影响较大的因素:提取时间、提取温度、水料比,根据中心组合(BoxBenhnken)实验设计原理对桑叶多糖的超声提取工艺进行优化,苯酚-硫酸比色法测定桑叶多糖的含量。在分析各个因素的显著性和交互作用的基础上,得到最佳提取工艺条件为:提取温度79.29℃、超声波时间35.90min、水料比8.78mL/g。采用该工艺条件,桑叶多糖的提取得率达到2.97%。与模型预测值相符。     

亚硫酸钠分银的试验研究

该文以铜阳极泥中间物料分金渣为原料,使用亚硫酸钠进行分银,对分银关键技术亚硫酸钠浓度、反应温度、反应pH值、反应液固比和反应时间进行了研究。并在生产实践过程中检测到亚硫酸钠浓度的准确性对生产有重要作用,试验探索了碘量法测亚硫酸钠浓度的影响因素,降低了亚硫酸钠浓度测量误差。在最佳工艺条件下,亚硫酸钠分银过程银的浸出率达到了98.9%。     

油页岩制油残渣制备氧化铝及其铝浸出率的研究

以抚顺东露天油页岩制油残渣为原料,用酸提法制备氧化铝,采用单因素考察法确定了抚顺东露天油页岩残渣提取氧化铝的酸溶反应最佳工艺条件为:煅烧温度850℃,煅烧时间1h,所需原料粒度0.074mm,盐酸浓度为12%,液固比为5∶1,酸溶反应温度100℃,反应时间1.5h,各项工艺指标在最佳工艺条件下,Al2O3浸出率为81.75%;采用均相化学沉淀法由酸溶反应得到的氯化铝滤液制备氧化铝的最佳工艺条件为:反应温度55℃,偏铝酸钠浓度0.4mol/L,乙酸乙酯与铝离子物质的量之比为1.7∶1,反应时间1.5h,表面活性剂的用量为总体系质量的0.3%。采用激光粒度分布仪、X射线衍射仪、X射线荧光光谱仪对所制得的产物氧化铝进行了表征和分析研究。     

真空下低价化合物法提取铝的新工艺--原料烧结实验研究

概述了我国炼铝工艺的现状以及铝冶炼方法的研究状况，并初步讨论与研究了煤烧结的一些基本规律。基于常规冶金存在的局限性以及真空冶金的优势，我们探索一种新炼铝的工艺，对低价化合物直接提取法作了一定的研究，低价化合物提取法主要包括了原料烧结实验、提取实验两大部分。本文着重研究了原料烧结实验部分中不同煤的配比，焦结温度对烧结团块性能的影响，得到最佳煤配比，焦结温度等重要的工艺条件和参数。它们是实验成功的关键。实验得到物料的最佳配比为10^#煤：5^#煤：16^#煤：工业Al2O3=3：7：10：5，最佳烧结温度为520℃。     

粗金真空蒸馏脱除银锌铜的研究

研究了真空蒸馏法脱除银锌铜的理论和实验的可行性。利用真空电阻炉,以质量分数为93.98%的粗金为原料,进行真空蒸馏实验,研究了蒸馏温度,蒸馏时间对金直收率及银锌铜的脱除率的影响。实验结果表明:在真空炉压强为10~30 Pa,蒸馏温度为1773 K,蒸馏时间为60 min的条件下,银的脱除率达到99%以上,锌的脱除率接近100%,残留物金中的铜含量低于2%,一次真空蒸馏残留物中金的直收率大于80%,此工艺为真空蒸馏分离粗金中银锌铜提供的新方法,并使银得到有效的富集,对粗金采用真空蒸馏法脱除银锌铜具有指导意义。     

火焰原子吸收光谱法测定载银沸石中银

研究了载银沸石中银含量的火焰原子吸收光谱测定方法.样品在低温下用硝酸溶解,试液过滤后直接用火焰原子吸收方法进行测定.实验结果表明:大量沸石对银的测定产生干扰,可通过配制沸石基质标准工作溶液消除干扰.在最佳实验条件下,银的质量浓度在0.40～15.00 g/ml与10.00～100.00g/ml范围内分别符合比尔定律,检出限为0.11g/ml,样品加标回收率为97%～103%.该方法可用于载银沸石中银含量的测定.     

钠化焙烧法回收废SCR催化剂中钒和钨的浸出机理及浸出动力学研究

鉴于废烟气脱硝催化剂具有浸出毒性的危险特性,环境保护部明确将废烟气脱硝催化剂纳入危险废物进行管理,同时由于废催化剂中含有高价值的钒钨钛成分,对废脱硝催化剂的资源化回收技术的研究成为近年来环保领域的热点。钠化焙烧可以破坏废催化剂原有的组织结构,使其中钒钨发生相变而提高浸出率,工艺简单,因此适用性广。2012年Kim等就采用钠化焙烧-水浸工艺回收废SCR催化剂中的钒和钨,并对焙烧过程机理进行研究,但目前对于钒钨浸出过程机理尚未有人研究。本工作是为了探究废SCR催化剂焙烧后浸出过程的反应机理,研究反应过程的控制条件,并进一步研究浸出过程动力学,从而使钒钨浸出反应的过程清晰明了,为提高浸出经济性提供理论基础。利用X射线衍射(XRD)和扫描电镜(SEM)对焙烧后样品的物相和形貌进行了分析,基于此设计了浸出过程的动力学模型,推导反应过程浸出方程,并通过浸出过程实验结果对浸出方程的参数进行推导。研究结果表明,焙烧后的试样呈柱状烧结相和针状非烧结相,两种相间几乎是完全分离的,钒、钨等主要存在于柱状烧结相中,因此适合对其进行直接水浸处理,使钒和钨溶出;根据焙烧形貌和假设,采用非端面柱状缩合模型推导了浸出过程动力学方程,得出浸出率和时间的函数关系。通过单因素实验确定了最佳的浸出条件为:液固比3∶1,浸出温度为80℃,搅拌速率为350 r/min,时间为30~40 min,此时钒和钨的回收率分别为90.07%和84.57%;通过回收率与浸出时间的关系换算出浸出率和时间的关系,并推导出钒、钨的浸出动力学方程为ηV=0.001 05t~2+0.066 2t+0.014 66和ηW=0.001 00t~2+0.064 12t+0.014 91。     

ITO废靶浸出过程研究

研究了铟锡复合氧化物(ITO)废靶回收工艺中的浸出过程,确定了最佳浸出工艺条件:温度363K;浸出后液酸度100g/L H2S04;浸出时间120 min;液固比8～12;ITO废靶粉粒度≤75μm.在此条件下,铟的浸出率大于99.5%,锡的浸出率为8.0%.     

纤蛇纹石的盐酸浸出及其动力学模型研究

研究了纤蛇纹石盐酸浸出过程中影响浸出率的主要因素,通过单因素实验确定最佳浸出条件为:盐酸浓度2 mol/L,温度95～100℃,浸出时间3 h,液固比60.进而通过建立液-固相反应纤维状颗粒的宏观动力学模型,研究了纤蛇纹石盐酸浸出的动力学过程.依据此模型所求得的反应表观活化能为24.4 kJ/mol,与用等浸出率法求得的值25.4 kJ/mol基本一致.动力学研究结果表明纤蛇纹石的盐酸浸出过程受扩散控制.     

合成工艺对Ag/NiFe2O4惰性阳极性能的影响

为得到制备Ag/NiFe2O4金属陶瓷惰性阳极的最佳工艺条件,利用正交试验法确定合适的工艺条件.考虑了主要影响阳极制品性能的五个因素,每个因素又设计四个水平,通过正交分析研究了各因素对制品密度、导电性、抗腐蚀性的影响.实验结果表明:Ag含量越多,导电性越好,但腐蚀率提高;提高烧结温度或延长烧结时间,有利于提高制品的密度,但导致Ag的溢出,抗腐蚀能力下降;压制压力越大,制品的致密度、抗腐蚀能力提高;粒度组成中大颗粒尺寸不能太大,否则腐蚀率增大、电导率下降.最佳工艺条件为:压制压力160 MPa;烧结温度1350℃;保温时间6 h;原料中主颗粒直径为0.50~0.355 mm;Ag含量为10%.     

Influence of mechanochemical pretreatment on leaching of silver in cyanide and non-cyanide medium

The leaching of silver from a mechanochemically pretreated silver-bearing complex sulphide concentrate of Peruvian origin (Casapalca) has been studied. The results with as-received concentrate have shown very low extraction of silver (up to 5.7%) in all cases of leaching. The mechanochemical pretreatment has caused 85% amorphization of tetrahedrite as silver-bearing mineral and an increase in the specific surface area of the concentrate from 0.3 m² g^?1 to a maximum value of 15.7 m² g^?1. This fact manifested itself in the subsequent process of silver extraction. By application of thiosulphate and thiourea leaching 99% recovery of Ag was reached already after 3-5 min of leaching.     

Response of low-grade gold ore to cyanidation and thiourea leaching

In this study, leaching tests were conducted on representative samples provided from Hamze-Qarnein gold deposit with grade of 0.8?ppm using cyanidation and thiourea leaching. Effective parameters including particle size, reagent concentration, oxidant concentration, pH, and dissolution time were examined in both cyanidation and acidic extraction with thiourea. Gold recovery and reagent consumptions (lime, cyanide, thiourea, ferric sulfate, and sulfuric acid) were measured under different leaching conditions. The results showed that cyanidation method was efficient with 95.21% gold recovery with following conditions: d₈₀?=?63?µm, pH 10.5, cyanide consumption of 1.23?kg/t, and 12?h cyanidation time. The acidic leaching using thiourea, required more chemical reagents and maximum gold recovery of 90.48% was achieved with thiourea consumption, leaching time, and pH equal to 13.32?kg/t, 5?h, and 1.7, respectively. According to the results, there was an interaction between ferric sulfate and thiourea concentrations and modeling of this process utilizing historical data design confirmed that the most effective parameter was the molar ratio of ferric sulfate to thiourea. Maximum recovery of gold obtained at molar ratio of 1/1. In addition, based on the experimental results, kinetics parameters of first-order reaction for gold dissolution were determined for cyanidation and thiourea leaching separately; therefore, for cyanidation, R_∞ and K were 95.59% and 0.59?h^?1 respectively, while R_∞ and K were in order of 78% and 0.87?h^?1 for acidic leaching using thiourea.     

A primary study of simultaneous leaching of silver containing manganese ore and a sphalerite concentrate

It is demonstrated that a low grade, silver containing manganese deposit can be exploited by reaction with a ZnS concentrate. In the process Mn(IV) is reduced to Mn(II) and the ZnS converted to ZnSO4. In the process Mn and Zn are solubilized. By studying the effects of quantity of reducing agent and sulfuric acid added and of time, temperature and liquid-to-solid ratio on the leaching process, the optimum technological conditions have been achieved under which the amount of manganese leached was 98%. The silver can be removed from remaining solids by adding ammonia liquor. By then adding hydrazine hydrate, sponge silver with purity up to 99% can be obtained with a recovery of 87%.     

Separation, preconcentration and determination of silver ion from water samples using silica gel modified with 2,4,6-trimorpholino-1,3,5-triazin

A new modified silica gel using 2,4,6-trimorpholino-1,3,5-triazin was used for separation, preconcentration and determination of silver ion in natural water by atomic absorption spectrometry (AAS). This new bonded silica gel was used as an effective sorbent for the solid-phase extraction (SPE) of silver ion from aqueous solutions. Experimental conditions for effective adsorption of trace levels of silver ion were optimized with respect to different experimental parameters in column process. Common coexisting ions did not interfere with the separation and determination of silver at pH 3.5 so that silver ion completely adsorbed on the column. The preconcentration factor is 130 (1 mL elution volume for a 130 mL sample volume). The relative standard deviation (R.S.D.) under optimum conditions is 3.03% (n=5). The accuracy of the method was estimated by using spring and tap water samples that were spiked with different amounts of silver ion. The adsorption isotherm of silver ion was obtained. The capacity of the sorbent at optimum conditions has been found to be 384 microg of silver per gram of sorbent.     

Investigation of the cyanide leaching optimization for ultrafine grinding gold–silver ore

ABSTRACT

In recent years, the ultrafine grinding (UFG) process has become increasingly important for the recovery of precious metals (especially for Au and Ag) from raw ores. It is well known that cyanide leaching of gold–silver ore has been an accepted process in the world. In the current study, UFG was proposed as a pretreatment method prior to cyanide leaching of a gold–silver ore. First, the ore was crushed and ground by jaw, cone crusher, and ring mill, respectively. Particle size of ground product was 75 µm based d₈₀. Second, the fine product was subjected to the grinding process by vertical wet stirred ball mill, and the final ultrafine product was used as leach feed material. The leach feed material had about d₈₀ = 20 µm and d₅₀ = 6.02 µm particle size. Some important leaching parameters were optimized by using the ultrafine powder in the study. The final leach experiments demonstrated that the recoveries of Au and Ag were 91.92% and 82.15% under optimum leaching conditions such as 150 kg/t quicklime dosage, 25% pulp density, 85°C leach temperature, 500 g/t cyanide concentration, and 90 h leaching time.     

Leaching behavior of pollutants in ferrochrome arc furnace dust and its stabilization/solidification using ferrous sulphate and Portland cement

In this study, dissolution properties under different conditions and pollution potential by toxicity characteristic leaching procedure (TCLP) of arc furnace dust generated in the production of ferrochrome were examined and some stabilization/solidification (S/S) techniques were applied to the dust depending on contaminants determined. Dissolution properties and pollution potentials of all the materials stabilized/solidified were also studied under the similar conditions. It was determined that the metallic components concentrations dissolved from the ferrochrome arc furnace dust (FAFD) except for chromium and zinc were below the detection limits. The chromium concentration dissolved from the FAFD by TCLP was found to be 9.8 mg/l. Portland cement (PC), PC-FeSO(4) and PC-sand-FeSO(4) mixtures for S/S of the FAFD were tested. Although metal ions in the cationic form were stabilized when the PC was only used, Cr(VI) in the sample was not changed depending on PC amount and remained in the soluble chromate form. The stabilization efficiency of Cr(VI) increased by the increasing amounts of PC and FeSO(4). The best S/S of the FAFD was accomplished when the 5 stoichiometric amounts of FeSO(4), 30% PC and 16% sand mixture were used. TCLP leaching results of the samples obtained under the optimum conditions were below the EPA landfilling limits.     

表面活性剂协同微波提取虎杖色素的研究

将表面活性剂辅助提取与微波辅助提取技术相结合用于提取虎杖色素,并对这种新的提取工艺进行了研究.研究结果表明:利用表面活性剂协同微波提取技术,通过优化工艺条件,可以大幅缩短提取时间和提高提取率,该法的优化条件为:原料为2 g虎杖干粉,提取剂为0.03?O-60%乙醇水溶液,提取剂用量为100 mL,微波功率为800 W,提取时间为0.0694h,提取次数为2次,与溶剂浸提取法和索氏提取法相比,每次提取时间分别由24 h和2 h减小为0.0694 h,提取率分别从77.2%和61.8%增加到98.9%.     

Characterisation and classification of solid wastes coming from reductive acid leaching of low-grade manganiferous ore

The present work was focused on the acid leaching process for manganese extraction in reducing environment to low-grade manganiferous ore that comes from Central Italy. The aim of this study was to establish optimum leaching operating conditions to reduce treatment costs of waste or, even better, to allow a waste valorisation as raw materials for other applications. Consequently, the main focus of the work was the characterization and classification of the solid wastes coming from the process carried out at different operating conditions; at the same moment the effect of process parameters on Mn extraction was also analysed. The effect of particles size on the manganese extraction in reductive acid leaching process was investigated, by using lactose as reducing agent. Particle size did not show a large influence on the Mn extraction yields in the investigated process conditions. This aspect suggests the use of the leaching waste for civil and/or environmental application: use of leaching solid wastes like filling material is to be applied, for example, for environmental restoration. The classification of the solid wastes, according to the Italian Laws about Release Test (RT), has demonstrated that the solid waste produced by leaching can be classifiable as "hazardous special waste". An improvement of solid washing let to reduce the SO(4)(2-) and an appropriate treatment is necessary to reduce the dangerousness of these solids. Possible application of ore and waste as raw materials in the ceramic industry was demonstrated not to be feasible.     

Electrodeposition of silver as a precursor matrix of magnetoresistive materials

The design of a bath able to electrodeposit silver at a relatively high negative potential was attained. The preparation of silver films at negative potentials in conditions at which dendritic growth is avoided, makes the process useful in silver-matrix magnetoresistive materials manufacture. Thiourea as a complexing agent was able to accomplish this purpose. Results indicate that thiourea bath produces homogeneous and fine-grained silver deposits with low sulfur content, avoiding hydrogen reaction in the potential range at which coherent deposits were obtained. Morphological and structural analysis were made as a function of temperature and the presence in the bath of other species.     

Chemical extraction of organic carbon to reduce the leaching potential risk from MSWI bottom ash

The performance of extraction solvents, including organic and inorganic solvents, for organic carbon extraction from municipal solid waste incinerator (MSWI) bottom ash was evaluated. The total carbon (TC) extracted was used to ascertain the efficiency of extraction solvents and the reduction of dissolved organic carbon (DOC) leaching potential was used to evaluate the capacity of solvents to minimize environmental impacts of MSWI bottom ash over short- and long-term considerations in landfill sites. Extract final pH value was a prominent parameter affecting TC extraction. The higher efficiency was obtained at the lower extract final pH and acid or neutral condition was necessary to achieve approximately 30% of TC extraction from bottom ash. On the basis of the results of TC extraction, the efficiency of organic carbon reduction was evaluated using organic carbon leaching potential. Hydrochloric acid was the best solvent to extract organic carbon in controlled pH conditions. Hydrochloric acid reduced the organic carbon leaching potential of MSWI bottom ash by about 68% at neutral leaching pH.