EFFECT OF MAGNESIUM AND SULFATE IONS ON KCl CRYSTALLIZATION IN A CONTINUOUS COOLING MSMPR CRYSTALLI2:ER

Crystallizations of KCl from water and reagent grade potassium chloride solution with and without magnesium sulfate and magnesium chloride as impurities were conducted in a one liter continuous MSMPR cooling crystallizer. A series of experiments at a constant operating temperature, various feed temperatures and magnesium and sulfate ions concentrations were carried out to investigate the effect of the type and concentration of impurities on the width of the meta-stable zone, crystal size distribution, crystal habit, crystal purity, growth rate, nucleation rate, and aggregation index. The width of the meta-stable zone increased with impurity concentrations of both magnesium and sulfate ions alike. Sulfate ion increased the mean crystal size at all concentrations, whereas the initial increase in mean crystal size at low magnesium concentrations was moderated at higher concentrations. Polycrystals formation was significant with and without impurities. The crystal surface became irregular at higher sulfate ion concentrations. The impurity incorporation within KCl crystals decreased with crystal size and was much higher in the case of magnesium sulfate. Secondary nucleation rate was unaffected and growth rate was altered in the presence of both impurities, and the influence was apparently independent of the effect upon the meta-stable zone width. The effect of impurities was suppressed with increase in suspension density.     

碱洗氧化工艺中杂质对硫酸钠结晶粒度的影响

针对碱洗氧化工艺脱硫废水中硫酸钠的蒸发结晶,设计开发了硫酸钠蒸发结晶放大实验装置,重点研究了废水中碳酸钠、铁离子和亚硫酸钠杂质对硫酸钠蒸发结晶晶体粒度的影响。结果表明：1.0%（质量分数）的碳酸钠对硫酸钠晶体的粒径影响可忽略;铁以沉淀物形式存在时,易引起硫酸钠晶体结块且粒径变小; 铁以溶解形式存在时,对硫酸钠晶体的粒径影响较小;亚硫酸钠的存在易引起硫酸钠晶体的粒径变小,氧化消除溶液中的亚硫酸钠后,结晶得到的硫酸钠晶体粒径变大。工业装置经过改造后,无水Na₂SO₄产品的平均粒径由106.71 μm提高至129.99 μm。     

离子膜电解盐水中杂质含量的控制

讨论精盐水中碘离子、钡离子和硫酸根等杂质对离子膜的影响,总结了控制这些杂质含量的措施。     

结晶法提纯钛白副产硫酸亚铁中杂质去除规律的研究

采用冷冻结晶工艺对钛白副产硫酸亚铁进行了提纯研究,重点考察了结晶母液循环时镁、锰杂质的累积情况以及它们的去除规律,同时对可能引入体系的钠杂质影响也进行了研究。通过多次结晶可以逐渐降低七水硫酸亚铁晶体中镁、锰杂质含量,但结晶母液的循环会导致体系内镁、锰杂质逐渐累积。利用结晶液与结晶体中镁、锰含量的关系曲线推断得到：当结晶液中镁含量低于298 mg/L时,七水硫酸亚铁晶体中镁质量分数将低于0.025%;当结晶液中锰含量高于761 mg/L时,七水硫酸亚铁晶体中锰质量分数将高于0.05%。另外,结晶法提纯硫酸亚铁时应避免向体系中引入钠离子,否则会导致七水硫酸亚铁晶体中钠杂质含量超标问题。该论文研究结果可以为利用结晶法提纯钛白副产硫酸亚铁提供一定的理论和技术指导。     

Si/F/K/Na杂质对硫酸钙结晶过程的影响

考察了湿法磷酸生产过程中Si, F, K和Na等杂质对CaSO4结晶过程的影响规律. 结果表明,两种碱金属对CaSO4结晶有不同作用,K有利于CaSO4晶体生长,而Na含量增加则会抑制CaSO4团聚;不同形式的K, Si和F对CaSO4结晶的作用不同,SiO2对CaSO4粒径影响不大,但会使其形貌不规则,H2SiF6会造成CaSO4晶体分散,而K2SiF6有利于CaSO4晶体生长.     

Particle Shape and Purity in Membrane Based Crystallization

Well‐controlled crystallization is the best method for preparing materials that are uniform in shape, size, structure and purity. The driving forces for crystallization are local gradients of supersaturation as the source and desupersaturation as the drain. Very high local supersaturation causes a high growth rate and represents a limiting factor for unstable modifications and product impurities. Hybrid membrane technology provides an interesting tool for controlling and limiting the maximum level of supersaturation due to defined mass transfer across the membrane. In this paper, the level of crystal growth rate in the system NaCl/KCl/water is varied by using different crystallization techniques. Vacuum evaporation crystallization (high growth rate) is compared to membrane based evaporation crystallization (low growth rate) and the results are interpreted in terms of product purity, particle shape and size. Membrane based crystallization in combination with effective solid/liquid separation as well as high performance analytics is suggested as a significant ultrapurification methodology.     

Specific Ion Effects of Salt Solutions on Colloidal Properties of Octadecylamine Hydrochloride

Flotation continues to be a major technique for the production of potash from low grade, complex systems containing a variety of ores and ions. The specific ion effects on the behavior of the flotation collector in the KCl flotation system becomes important to the interpretation of the flotation mechanism. In this work, specific ion effects on the turbidity, surface tension and aggregation behavior of the common collector in KCl flotation, octadecylamine hydrochloride (ODA), have been investigated. The results from turbidity and surface tension studies of ODA solutions show that both cations and anions can affect the colloidal properties of ODA. Molecular dynamics simulations show that the binding that energy barrier between ODA headgroups and anions is principally responsible for the specific anion effect of γ _CAC of ODA solutions. In addition, the ion effect on the ODA aggregation particle size was also studied by using transmission electron micrographs (TEM) and dynamic light scattering. The data reveal that the presence of salt ions can induce the formation of larger ODA colloidal particles, on which the cation effect is more significant. This work provides detailed information of specific ion effect on colloidal properties of ODA, which may promote a further understanding of the flotation mechanism and help to improve the flotation of KCl from brine sources.     

第一讲——毒害物、非毒害物、药物与灾害(一)

从2010年起,国家开始重点整治重金属污染,铅、镉、铬、汞与类金属砷是重中之重。国家有关部门与地方政府相继出台了更加严厉的污染事故惩罚措施,如明确各级政府的一把手是污染事故的第一责任人,将严追责任。四川省环保厅表示,对于直排、偷排企业,一旦查实,立即关门取缔。央视与地方台陆续曝光了一些电镀、印制板、采矿企业的严重重金属污染状况,各地新闻媒体与主管部门也分别加强了监督与执法力度。从2010年7月1日起,无论新旧电镀厂点都开始执行排放限值更严格的新排污标准GB21900–2008。众所周知,电镀作业会产生多种重金属与有害有机物,整治首当其冲。为什么要重点整治重金属污染?只有对其毒理学基本知识有所了解后才能主观自觉地、一丝不苟地执行。本刊开办金属毒理学知识讲座的目的正在于此。愿能对相关企业人员有所帮助,尽一份社会责任。     

熔盐法合成Bi_3NbTiO_9陶瓷粉体

利用氯化钾作熔盐,采用熔盐方法利用高温煅烧制备了Bi3NbTiO9陶瓷粉体,研究了煅烧温度,保温时间和粉体合成之间的关系。结果表明:氧化钾能够有效降低Bi3NbTiO9粉体的合成温度和提高粉体的合成速率。熔盐方法获得纯Bi3NbTiO9相的温度要比固相方法降低约150℃。和保温温度相比较,保温时间对晶粒尺寸的影响有限。     

甲苯法己内酰胺中290nm吸光值的杂质分析

利用VP-ODS 250 mm×4.6 mm液相色谱柱,流动相为乙腈/水(体积比12/88),1.25 mmol/L磷酸调节酸度,流速1 mL/m in,建立了甲苯法生产的己内酰胺(CPL)中影响290 nm吸光值的杂质的高效液相色谱分析方法。采用大孔径离子树脂和活性炭吸附富集这些微量的杂质,通过液相色谱-质谱联用(LC-MS)和气相色谱-质谱联用(GC-MS)对杂质进行了定性分析。结果表明:该方法稳定可靠,可用于CPL杂质含量控制。LC-MS和GC-MS分析表明,CPL中影响290 nm的吸光值的主要杂质为苯甲腈、2-甲基-8-羟基喹啉、2,6-二氨基吡啶、邻-乙基环己酮肟和相对分子质量为220的物质。     

卤水结晶除杂工艺技术研究

介绍利用结晶器进行卤水除杂的一种工艺。旧工艺碳酸钠和氢氧化钠直接加入卤水除杂,容易产生碳酸钙和氢氧化镁胶体沉淀,难以过滤。采用结晶除杂工艺,减小钙镁的反应浓度,同时减小除杂剂离子的浓度,使生成杂质晶体的过饱和度得到控制。该工艺很好地控制杂质沉淀结晶的粒径,较好地解决盐泥的固液分离。实验验证了影响杂质结晶生长的因素。实验结果对比了卤水结晶除杂与传统除杂的盐泥分离效果,得到的结晶除杂盐泥抽滤速度比传统盐泥抽滤快30倍。     

Preparation and crystallization kinetics of micron-sized Mg(OH)2 in a mixed suspension mixed product removal crystallizer

Magnesium hydroxide is an important chemical, and is usually obtained from seawater or brine via precipitation process. The particle size distribution of magnesium hydroxide has great effects on the subsequent filtration and drying processes. In this paper, micron-sized magnesium hydroxide with high purity, large particle size and low water content in filter cake was synthesized via simple wet precipitation in a mixed suspension mixed product removal (MSMPR) crystallizer. The effects of reactant concentration, residence time and impurities on the properties of magnesium hydroxide were investigated by X-Ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Malvern laser particle size analyzer. The results show that NaOH concentration and residence time have great effects on the water content and particle size of Mg(OH)₂. The spherical Mg(OH)₂ with uniform diameter of about 30 μm was obtained with purity higher than 99% and water content less than 31%. Furthermore, the crystallization kinetics based on the population balance theory was studied to provide the theoretical data for industrial enlargement, and the simulation coefficients (R²) based on ASL model and C-R model are 0.9962 and 0.9972, respectively, indicating that the crystal growth rate of magnesium hydroxide can be well simulated by the size-dependent growth models.     

钙镁离子对二氧化钛光催化氧化水中腐殖酸的影响

考察了间歇反应器中钙离子存在下腐殖酸分子在TiO2颗粒表面的吸附行为,进而以125 W (Emax=365 nm) 汞灯为中心光源,考察了钙镁离子对二氧化钛光催化氧化水中腐殖酸的影响. 结果表明,在腐殖酸初始浓度C0=20 mg/L, [Ca2+]=80 mg/L, pH=7和TiO2=1 mg/ml实验条件下,经2.5 h的光催化反应,腐殖酸的脱色率为100%,氧化分解率接近100%,矿化率大于95%.     

Investigation of Selectivity and Kinetic Behavior of Strong‐Base Ion Exchange Resin Purolite A 520E for Nitrate Removal from Aqueous Solution

Abstract

The aim of this work is to present experimental results on the removal of nitrate by nitrate selective ion exchange resin, Purolite A 520E. The resin particle size, nitrate concentration, temperature, and stirring speed were investigated as experimental parameters and the optimum conditions for nitrate removal were determined. Nitrate removal by strong base anion exchange resin Purolite A 520E was carried out with the batch method in the presence of chloride and sulfate ions. The existence of a high concentration of competing ions in a solution resulted in a reduction of nitrate removal. Nitrate removal ratios decreased from 98% to 85% and 88%, respectively, in the presence of chloride and sulfate ions when the chloride and sulfate ratios were increased in solution. The process kinetics were predicted by using Homogenous Diffusion Models. It was seen that about 98% of nitrate in the aqueous solution could be removed using optimum conditions.     

仲钨酸铵中杂质的分析方法

文章采用分光光度法对仲钨酸铵中的杂质进行了测定,主要测定了反应温度、反应时间、NaOH浓度和搅拌速度对黑钨矿中有效成分钨浸出的影响;同时还考察了树脂的性能、交换前溶液的浓度和流速、解吸剂的浓度、流速和温度等因素在离子交换过程中对除杂率的影响以及在结晶过程中温度对仲钨酸铵晶体的影响。     

氯酸钠生产中母液处理工艺研究

目前,在氯酸钠生产中常用化学沉淀法处理硫酸根,但是会产生大量含铬污泥,污染环境。提出利用离子交换树脂和纳滤膜装置综合处理结晶母液的方法,既能回收重铬酸钠又能脱除硫酸根。实验结果表明,重铬酸钠的回收率可达98%,结晶母液处理后硫酸钠质量浓度低于3 g/L,达到母液循环利用的要求。     

EFFECT OF FERROUS AND FERRIC IRON IMPURITIES ON THE CRYSTALLIZATION OF GYPSUM AND SLUDGE FORMATION IN WET-PROCESS PHOSPHORIC ACID

The effect of ferrous and ferric iron on the crystallization of calcium sulfate dihydrate, the rate of filtration, and the precipitation of sludge in concentrated acid were investigated. A bench scale unit was used to simulate dihydrate plant conditions. It was found that ferrous iron was oxidized to ferric, and the behavior of the two impurities in the acid was therefore very similar. At low levels of impurities, ferrous and ferric iron improved filtration, but further additions decreased it. Sludge collected from the concentrated acid after five weeks was mainly calcium sulfate hemihydrate and anhydrate. With the addition on 0.5% and 0.75% iron impurities however, the presence of (Fe,Al) 3 KH 14 (PO 4 ) 8 ·4H 2 O was evident in electron micrographs.     

Effect of ferrous and ferric iron impurities on the crystallization of gypsum and sludge formation in wet-process phosphoric acid

The effect of ferrous and ferric iron on the crystallization of calcium sulfate dihydrate, the rate of filtration, and the precipitation of sludge in concentrated acid were investigated. A bench scale unit was used to simulate dihydrate plant conditions. It was found that ferrous iron was oxidized to ferric, and the behavior of the two impurities in the acid was therefore very similar. At low levels of impurities, ferrous and ferric iron improved filtration, but further additions decreased it. Sludge collected from the concentrated acid after five weeks was mainly calcium sulfate hemihydrate and anhydrate. With the addition on 0.5% and 0.75% iron impurities however, the presence of (Fe,Al) 3 KH 14 (PO 4 ) 8 ·4H 2 O was evident in electron micrographs.     

由铁矿烧结电除尘灰浸出液制备氯化钾及球形碳酸钙

采用物理化学表征方法研究了包钢烧结电除尘灰的基础性质,结果表明,该烧结电除尘灰的主要成分为Fe,K,Na,Ca的化合物,其中的钾盐可通过水浸分离回收. 浸出液中含有大量可溶性硫酸钙. 为了在浸出过程中抑制硫酸钙的溶解,考察了硫酸钙在KCl,NaCl,K2SO4及其混合盐中的溶解性能. 结果表明,由于KCl和NaCl的盐溶效应,硫酸钙的溶解性能得到提升. 应采用低液固比,提高浸出液中硫酸根离子的相对含量,利用硫酸根离子的同离子效应抑制烧结电除尘灰中硫酸钙的溶解. 以碳酸钠为沉淀剂,考察其对钙离子沉淀效果的影响. 结果表明,碳酸钠具有较好的硫酸钙沉淀效果. 在沉淀钙离子的同时,研究了沉淀剂的浓度、反应温度、搅拌强度对碳酸钙晶体形貌的影响,制备获得了分散良好,粒径小于10 mm的球形碳酸钙副产品,实现了资源综合利用. 最后设计了从烧结电除尘灰提取国标20406-2006一级氯化钾并联产球形碳酸钙副产品的工艺路线,该工艺具有工业应用潜力.     

(NH4)2SO4和Na2SO4混合溶液中(NH4)2SO4结晶动力学及铁/铝/锰/铬等离子对(NH4)2SO4结晶的影响规律

湿法冶金、三元前体制备等过程均会产生含硫酸钠与硫酸铵的高盐废水。研究高盐废水中硫酸铵的结晶动力学,并考察常见金属离子的影响规律对高盐废水处理具有重要意义。本文以含硫酸钠与硫酸铵混合溶液中硫酸铵的结晶过程为例,系统考察了硫酸铵的结晶动力学及铁、铝、锰、铬对硫酸铵结晶的影响规律。含硫酸钠与硫酸铵混合溶液硫酸铵结晶动力学研究结果表明,硫酸铵生长速率和成核速率方程分别为为B=1.303×10^-16G^1.069M_T^1.801,G=15.708σ^1.387;在硫酸钠与硫酸铵混合体系中,溶液过饱和度影响硫酸铵成核及生长速率,溶液过饱和度减小,晶体的成核及生长速率都会减小,与单体系硫酸铵结晶动力学结果相比,动力学参数均有所下降。铁、铝、锰、铬对硫酸铵结晶的影响规律研究结果表明,铁、铝抑制了硫酸铵晶面生长,结晶粒度减小;锰、铬对硫酸铵结晶有一定的促进作用,结晶粒度增大。金属离子改变了硫酸铵晶习,锰使结晶呈现三棱柱状,铁、铝使硫酸铵结晶片状生长。不同金属离子条件下的结晶动力学方程表明,铁和铝对结晶...