强螯合物废水的处理方法第二部分——螯合沉淀法处理混合电镀废水

比较了液态螯合树脂DTCR处理法与碱沉淀法的性能。DTCR法处理混合电镀废水的流程主要包括(1)调整pH,(2)加入1%～2%(质量分数)DTCR,(3)加入絮凝剂,(4)搅拌,(5)过滤。处理含Cr(VI)废水时,建议在加入DTCR前先用NaHSO3将Cr(VI)还原为Cr(Ⅲ)。列出了处理不同重金属时所需DTCR的量。采用DTCR法处理含40g/LCu2 、28g/LNi2 和26g/LZn2 的电镀废水后,排出水中重金属含量低于0.5mg/L,完全符合国家排放标准。     

液体型锌硼体系水溶肥料稳定性初探

开展了液体型锌硼体系水溶肥料稳定性的研究,考察了反应物配比、pH、温度和静置时间对体系稳定性的影响.试验结果表明:硼砂含量增加至一定程度,体系出现沉淀,且随着pH提高,沉淀量增加.当pH≤5时,沉淀物为H3 BO3;当pH =6时,沉淀物为Zn(OH)2和Zn( HSO4)2.在pH =3时,常温和50℃静置过程中均会...     

螯合沉淀法处理含铬电镀废水

以NaHSO3为还原剂,新型重金属离子捕集剂DTCR为螯合剂,采用螯合沉淀法处理含铬电镀废水。研究了还原剂投加量、还原反应阶段的废水pH、螯合剂投加量、絮凝剂(PAM)投加量、螯合沉淀阶段的废水pH和搅拌时间对处理效果的影响。还原反应的较优工艺为:NaHSO3200mg/L,废水pH1.84,搅拌时间30min。螯合沉淀的最佳工艺条件为:DTCR70mg/L,PAM8mg/L,废水pH8.0,搅拌时间40min。采用最佳螯合沉淀工艺处理含铬电镀废水时,总铬去除率在95%以上,出水总铬为0.14mg/L,且未检测到其他重金属离子,可达标排放。     

碱性锌镍合金电镀和钝化废水的组合处理工艺

向碱性锌镍合金电镀与钝化混合废水中加稀盐酸,调节其pH至4～6后加入氯化亚铁,再用石灰乳液调节pH至10～12,利用亚铁离子和钙离子的协同作用来沉淀羧酸配位剂,三价铬离子生成氢氧化物沉淀.过滤分离沉淀物后以稀盐酸调节上清液的pH至4.5～5.5,加二甲基二硫代氨基甲酸钠沉淀镍、锌、钴等离子.再次过滤分离沉淀物后以氢氧化钠溶液调节废水的pH至6～8,用生化降解法降低其化学需氧量.该工艺成本低,处理结果至少可满足GB 21900-2008《电镀污染物排放标准》的"表2"要求.     

重金属离子捕集剂处理含Cu2+废水的工艺研究

目的：合成水溶性二硫代氨基甲酸钠螯合树脂（DTCR）,评价其对含铜废水的处理效果。方法：利用含铜废水考查自合成物（DTCR）的除铜能力。控制废水pH值、重捕剂以及絮凝剂（聚丙烯酰胺）加入量,搅拌一定时间后,静置,过滤,采用原子吸收法测定滤液中Cu2＋的含量。结果：在反应时间为6小时,重捕剂加入量为0．3mL,聚丙烯酰胺（浓度为0．9mg／L）加入量为0．8mL,pH值为4-10时,废水中Cu2＋的去除率可达到98％以上,经过处理的废水达到国家排放标准（GB8978-1996）。     

重金属离子捕集沉淀剂DTCR处理含镉废水工艺研究

用改进的单叶直式搅拌器,采用分段搅拌法,以重金属离子沉淀剂DTCR处理含镉废水,着重考察了搅拌强度、时间对除镉的影响,生成的沉淀在不同pH条件下进行了溶出实验。结果表明,对1 L含镉废水,260 r/min加入0.3%DTCR 4.4 mL,搅拌1.5 min;120 r/min加入0.1%PAM0.8 mL,搅拌1 min;40 r/min搅拌8 min,镉除去率>99%,反应时间10.5 min,沉降15 min。其工艺特点:DTCR直接投放,不调整废水pH,镉及共存金属离子同时处理,工艺简便,条件温和,清液达标。溶出实验显示,沉淀的化学性质稳定,不造成二次污染。     

混凝沉淀-Fenton氧化法处理工业烟草废水研究

通过混凝沉淀-Fenton氧化法处理工业烟草废水.实验结果表明,原废水初始COD为580 mg·L-1,pH=7.混凝沉淀中,当PAC加入量4 mL、PAM加入量1mL、pH=7、环境温度为32℃时,混凝效果最好,COD去除率能达到73％;Fenton氧化处理混凝后废水,当n(H2O2):n(Fe2+)=30:1、H2O2加入量为2 mL、反应pH=3时,Fenton氧化效果最好,COD去除率能达到77％.通过两者联合作用处理后的污水再经生物处理后即可达标排放.     

工业硫酸锰中钙、镁的净化研究

采用氟化锰作为沉淀剂对工业硫酸锰中的钙、镁进行净化研究。通过单因素实验和正交试验考察了溶液pH、反应温度、氟化锰加入量对钙、镁净化率的影响。实验结果表明,影响钙、镁沉淀率的因素最主要的是氟化锰的加入量,其次为反应温度、溶液pH。在实验中,当氟化锰加入量为1 g、反应温度为90 ℃、溶液pH为4.5时,钙、镁的净化率分别为83%和85%。采用氟化锰作为沉淀剂净化工业硫酸锰中的钙、镁是可行的,该方法操作方便,并且不会引入新的杂质。     

Al_2O_3-TiC纳米复合粉体在水基体系中分散性的研究

本文研究了分散剂PEG和MN对Al2O3-TiC纳米复合粉体在水中分散性的影响。采用沉降实验、透光率、激光粒度分析以及透射电镜分析等考察了分散剂的用量、pH值等因素对Al2O3-TiC水悬浮液稳定性的影响,并对其分散机理进行了探讨。实验结果表明,不添加表面活性剂的情况下,当复合粉末的悬浮液pH为8时,溶液的分散稳定性最好。当悬浮液的pH为8时,随PEG和MN加入量的不同,悬浮液的沉降量不同。当PEG的加入量为0.03g,MN的加入量为0.02ml时,其72h最小沉淀量分别为1.17ml和0.13ml,这表明加入适量分散剂MN的纳米Al2O3-TiC水悬浮液稳定性更好。在最佳MN添加量的情况下,当溶液的pH为8时,试样沉降量最少,其分散稳定性最好。     

共沉淀法制备掺钕钇铝石榴石纳米粉末反应机理的研究

采用共沉淀法,以Al（NO3）·9H2O,Y2O3,Nd2O3和NH4HCO3为原料,正硅酸乙酯为添加剂,制备出Nd：YAG纳米前驱体粉末。探讨了共沉淀法制备Nd：YAG纳米粉末的反应机理。研究结果表明：当pH值达到2．97时溶液出现沉淀;混合溶液生成沉淀物是由Al^3＋的沉淀所决定的;Al^3＋首先均相成核,随后Y和Nd离子以A1沉淀物为异相核发生异相成核,形成的碳酸钇正盐均匀地包覆在碳酸铝沉淀物的表面上,形成核壳结构。     

锌冶炼渣浸出模拟液铁沉降试验研究

实验研究了不同反应条件的铁沉降效率及锌、镉损失率。结果表明,氧气做氧化剂pH为3.0~3.5时,反应7 h后,铁沉降效率不高,仅达到34%,锌、镉损失率随反应时间的增加而增加。铁沉降效率随pH及温度的升高而增大,SEM和XRD分析表明,pH为3.0时的沉铁渣中主要成分是针铁矿。     

Preparation of highly acidic hydrated niobium oxide

In order to obtain a highly acidic hydrated niobium oxide, the preparation methods and conditions such as niobium precursors, precipitating reagents, treatment of precipitates, washing of precipitates, final pH in precipitation, and calcination temperature were systematically examined. Strong acidic sites of H₀−8.2 were found to appear on hydrated niobium oxide when the oxide was prepared by boiling the precipitates, which were obtained by hydrolysis of niobium oxalate with KOH, in a diluted mild acid solution(preferably 0.1N HNO₃) followed by washing with hot water several times and heating in air at 300 °C. Final pH in the precipitation must be below 11.     

Mechanisms of formation of iron precipitates from ferrous solutions at high and low pH

The oxidation and subsequent precipitation of iron from solutions are very important for most hydrometallurgical wastewater treatment practitioners. The particle formation process mechanisms are important for shaping the dewaterability and particle size distribution of the precipitates. In this study the objective is to elucidate the mechanisms of iron particles formation from ferrous solutions at high (pH 9.0) and low pH (pH 6.0). The results obtained showed that the precipitation process is dominated by nucleation at the initial stages and aggregation dominated at the final stages. The precipitates formed at higher pH transform faster and result in the formation of more stable precipitates. Precipitates formed at pH 6.0 are larger but less stable chemically. The results may mean higher throughputs and lower costs of post precipitation stabilisation for operations at higher pH. The benefits for operation at lower pH would be a better solid-liquid separation due to the bigger sized particles formed.     

A study on nickel hydroxide crystallization characteristics

The precipitation characteristics of nickel hydroxide as well as carbonate and sulfide were studied to determine the proper treatment condition of the wastewater induced from nickel-plating industry. When the pH value was maintained higher than 10, the nickel concentrations in the effluent could be kept lower than 5 mg/l. The precipitation of nickel salts in the model wastewater was conducted by alkaline addition, such as the uses of sodium hydroxide, sodium carbonate, sodium bicarbonate and sodium sulfide. In case of sulfide treatment, the nickel concentration of treated wastewater showed the lowest value after the removal of precipitates. The change of particle size of the crystal precipitates by the precipitation conditions and precipitants was also investigated. In spite of the various precipitation conditions that were adopted, the change of particle size of the crystal precipitates showed no great differences. The settling rates of the precipitated particles were observed and the free settling period was terminated within 20 minutes. Although the hindered settling as well as bed compaction progressed subsequently, the bed heights were maintained almost the same level after few hours later     

不同pH下涂装废水中沉淀物形成的计算模拟预测及验证

采用中和沉淀法处理涂装废水,在不同pH（4~12）下研究了涂装废水中总磷、硫酸根等阴离子和总铁、总铅、总铬等主要的阳离子去除效果,并利用修正后的热力学方程Gibbs函数△G=RTln（Q_c/K°_sp）对pH调节过程中沉淀形成机制进行讨论。结果表明,pH=2.18~10时离子强度I在0.10mol/L左右,pH=12时离子强度I为0.59mol/L;考虑离子强度I影响时沉淀产物的活度积K°_sp与溶度积K_sp相比最大,可相差15个数量级,对于涂装废水沉淀产物生成预测时应采用活度积K°_sp进行判定;pH对弱酸弱碱各型体的存在浓度影响很大,pH=4~8时形成的沉淀产物主要为磷酸盐,pH=10~12时氢氧化物沉淀种类增加,pH=12时形成的沉淀产物种类最多。     

Phase equilibria for salt-induced lysozyme precipitation: Effect of salt concentration and pH

The salt-induced precipitation of lysozyme from aqueous solutions was studied at 25 °C and various pH values by cloud-point investigations, precipitation experiments (analysing the compositions of the coexisting phases) and microscopic investigations of the precipitates. Sodium sulphate as well as ammonium sulphate were used to induce the precipitation. The experimental results are discussed and used to develop a scheme of the phase equilibrium in water-rich aqueous solutions of lysozyme and either Na₂SO₄ or (NH₄)₂SO₄.     

Spontaneous fractal ordering of zirconium oxide nanoparticles during synthesis from solution

The effect of synthesis conditions (pH of zirconium hydroxide precipitation) on the fractal structure of yttrium-stabilized zirconium oxide has been investigated. It has been found that the better pH of precipitation of zirconium hydroxide for obtaining soft-agglomerated nanoparticles ZrO₂ is ～4.5. It has been determined by small-angle X-ray scattering (SAXS) that the mass-fractal aggregation of precursors contributes to a good filtration of hydroxide precipitates and allows preparation of oxides with soft, readily destructible aggregates.     

Arsenic(V) removal from enargite leach solutions by precipitation of magnesium ammonium arsenate

This study investigated a potential method for the removal of arsenic from enargite leach solution containing 5.86 g/L As(V) by precipitation of magnesium ammonium arsenate (MAA). The experimental results showed the As(V) concentration can be reduced to 1.8 mg/L under the optimum conditions. The molar ratio NH₄/Mg/As in precipitates formed at different pH values was checked by wet chemical analysis, indicating that some of by-products such as Mg₃(AsO₄)₂, Mg(OH)₂, and MgHAsO₄ will be formed at the solution pH above or below pH 9.5. Notably, this study indicated MAA has a better ability for arsenic removal than magnesium arsenate. The precipitates also were characterized by XRD and SEM.     

钙化提钒溶液沉钒的影响因素及沉钒动力学

用(NH4)2SO4对钒渣钙化焙烧、稀酸浸取、化学沉淀净化后的酸性含钒溶液进行沉淀富集,考察了钒浓度、初始pH值、加铵系数(NH3/V摩尔比)、沉钒温度和时间对沉钒率及V2O5含量的影响,研究了沉钒动力学,对沉钒产物进行了表征. 结果表明,在初始pH为2.00?0.05、加铵系数1.5、温度大于95℃、沉钒时间120 min、钒液中V浓度大于20 g/L的条件下,沉钒率超过96%,产品中V2O5含量大于98%,杂质含量符合98级氧化钒的国家标准. 75~99℃下的沉钒过程可由Avrami动力学方程描述,表观活化能Ea=93.23 kJ/mol,指前因子A=9.14×1011 min?1. 铵盐沉钒产物为(NH4)2V6O16?1.5H2O,高温煅烧所得V2O5晶体为柱状,平均粒径1.25 ?m,主要杂质Mn以MnV2O6形式存在.     

pH调整剂对含砷酸性废水中氧化Fe（Ⅱ）共沉淀固砷行为的影响

双氧水催化氧化Fe（Ⅱ）共沉淀砷的过程中,采用不同的pH调整剂调节溶液的pH,研究了不同的pH调整剂对废水中砷沉淀效果及沉淀渣性质的影响。结果表明：采用Na₂CO₃和CaO作为pH调整剂时有利于废水中砷的脱除,生成的共沉淀渣中砷主要是以无定形的非晶态块状颗粒形式存在的;使用Na₂CO₃作为pH调整剂时最有利于沉淀渣颗粒的长大,所得沉淀渣粒径最大,但是砷渣的稳定性最差,更容易从渣中释放出砷;采用CaO获得的沉淀渣中由于CaSO₄棒状颗粒的存在,渣的粒径相对较小,但砷的存在形式最为稳定,固砷效果最好。