Nickel electrowinning using a Pt catalysed hydrogen-diffusion anode. Part II: Batch tank with a sulphate bath

A batch tank of 1.6L capacity has been designed for Ni electrowinning using a Pt catalysed H₂-diffusion anode and a stainless steel/Ni cathode, both of 100cm² area. The anode has high stability for sulphate baths of pH3.5 with 35gL^–1 H₃BO₃ and Ni²⁺ concentrations from 10gL^–1 up to saturation. Linear correlations between the cell voltage and current intensity are found, as expected for ohmic control of the process. Good electrowinning conditions at room temperature are obtained for Ni²⁺ contents from 50gL^–1, using an interelectrode gap of 2cm and regulating the solution pH by NaOH addition for periods of 30min. Current efficiencies 93% are always found. The energy costs increase linearly with increasing current density from 10 to 50mAcm^–2, with values much lower than those obtained using a conventional lead anode. This indicates that the Pt catalysed H_{_2}-diffusion anode is preferable for Ni electrowinning. The crystals are composed of high-purity Ni and have a face-centred cubic structure. Surface analysis by SEM shows that the grain size gradually increases with increasing current density, with no significant influence of the Ni²⁺ concentration.     

硫酸亚铁制备高品质氧化铁红的新工艺研究

对钛白副产物硫酸亚铁制备高品质氧化铁红的新工艺进行了研究。本工艺以生产钛白粉的副产物硫酸亚铁为原料,通过化学方法净化钛白副产物硫酸亚铁,除杂后得纯净的硫酸亚铁,再经过脱水、煅烧等工序,得到铁磁体用氧化铁红。通过实验得到了制备高品质氧化铁红的最佳工艺条件。在最佳工艺条件下,制得的氧化铁红纯度高达99.8%,另外,所制得的氧化铁红产品还具有其他物理性能指标,如产品的晶型为α型三氧化二铁,平均粒度小于1.5 μm,松装密度小于0.35 g/cm³,水质量分数小于0.5%。     

低品位软锰矿制备硫酸锰绿色工艺研究

利用广西低品位软锰矿与硫酸为原料,硫酸亚铁作还原剂制备硫酸锰.通过正交实验得出硫酸锰浸取过程的较优工艺条件为:还原剂量为理论用量的110％,硫酸为理论用量的90％,反应时间3.5h,反应温度80℃.在此条件下,锰浸取率可达97.43％.通过鼓入空气的方法,将Fe2+氧化成Fe3+,再水解除去.在氧化温度75℃、鼓人空气...     

磷肥厂低浓度氟硅酸制冰晶石的研究

介绍了利用中小磷肥厂副产的氟硅酸制冰晶石的新工艺,以低浓度的氟硅酸和碳酸氢铵、硫酸铝、硫酸钠为原料制取冰晶石,并副产硫酸铵和白炭黑。研究了各种因素对产品质量的影响,制得了符合国标规定的质量要求的产品和副产品,新工艺的优点是原料综合利用好,可制得n（NaF／AlF3）接近3．0的冰晶石,经济效益好,无污染。     

污泥浓缩、脱水滤液除磷试验研究

污泥由浓缩到脱水过程中会因为在缺氧环境中停留时间过长而释放大量的磷,从而直接影响出水总磷的排放。仪化污水处理场生产、生活污水的总磷质量浓度基本在10mg/L以下,而场内污泥浓缩、脱水过程中排放的回流水总磷的最大质量浓度达到40mg／L,这部分磷对装置出水总磷的合格排放将产生重要的影响。利用物理化学法,在回流水中投加有机或无机混凝剂,可去除大量的磷。实验证明,当回水中TP的质量浓度为20mg/L左右时,工业硫酸铝的投加量达40mg／L,即能获得80％以上的除磷效果,同时还能去除40％左右的COD。     

KCl-K2SO4-Na2SO4系统低温融体形成的温度范围

KCl-K2SO4-Na2SO4系统低温融体是引起新型干法水泥预分解系统结皮堵塞至关重要的因素.融体的熔点越低,低温融体对粉状物料的粘结能力越强,因而对结皮堵塞的影响也越大.用化学试剂和实验电炉进行实验,绘制了KCl-K2SO4-Na2SO4低温融体形成的温度范围图.结果表明:KCl-K2SO4-Na2SO4三元系统共融温度＜800℃,最低共融温度＜500℃,相当大范围的共融温度在500～700℃.在Na2SO4含量较高的情况下共融温度低,预示其对结皮影响比K2SO4的更大.     

硫酸钙晶须填充UHMWPE复合材料的摩擦磨损性能

以硫酸钙晶须(CSW)作为填料填充改性超高分子量聚乙烯(UHMWPE),采用热压成型法制备了不同硫酸钙晶须含量的UHMWPE/CSW复合材料;在销-盘摩擦磨损试验机上考察了硫酸钙晶须对UHMWPE/CSW复合材料摩擦学性能的影响,利用扫描电子显微镜对UHMWPE复合材料的磨损表面进行了微观分析。结果表明:随着硫酸钙晶须填充量的增加,复合材料的硬度逐渐增大,耐磨性能逐渐增加,摩擦因数逐渐减小;当硫酸钙晶须填充质量分数为20%时,UHMWPE/CSW复合材料的摩擦学性能最好。     

硫酸盐侵蚀环境下基于B3模型的混凝土抗压强度时效分析

基于B3模型,建立了持续荷载下混凝土抗压强度的时效模型.通过考虑持续荷载和硫酸盐共同作用对混凝土截面有效应力的影响,建立了持续荷载和硫酸盐共同作用下混凝土抗压强度的时效模型.经分析,持续荷载和环境因素是影响混凝土抗压强度时效水平主要的因素,而混凝土强度等级对强度时效水平的影响较小.     

Characterisation of thermostable trypsin and determination of trypsin isozymes from intestine of Nile tilapia (Oreochromis niloticus L.)

Trypsin from intestinal extracts of Nile tilapia (Oreochromis niloticus L.) was characterised. Three-step purification – by ammonium sulphate precipitation, Sephadex G-100, and Q Sepharose – was applied to isolate trypsin, and resulted in 3.77% recovery with a 5.34-fold increase in specific activity. At least 6 isoforms of trypsin were found in different ages. Only one major trypsin isozyme was isolated with high purity, as assessed by SDS-PAGE and native-PAGE zymogram, appearing as a single band of approximately 22.39 kDa protein. The purified trypsin was stable, with activity over a wide pH range of 6.0–11.0 and an optimal temperature of approximately 55–60 °C. The relative activity of the purified enzyme was dramatically increased in the presence of commercially used detergents, alkylbenzene sulphonate or alcohol ethoxylate, at 1% (v/v). The observed Michaelis–Menten constant (K_m) and catalytic constant (K_cat) of the purified trypsin for BAPNA were 0.16 mM and 23.8 s⁻¹, respectively. The catalytic efficiency (K_cat/K_m) was 238 s⁻¹ mM⁻¹.