Surface chemistry considerations in the flotation of bastnäsite

Bastnäsite is the chief valuable mineral in two of the world’s largest rare earth (RE) mineral deposits and is also found in a number of new RE deposits currently under development. This work used electrophoretic and electroacoustic zeta potential measurements to identify the interaction between bastnäsite and several different collectors. The results of these measurements were then compared with microflotation of bastnäsite and quartz, a common RE gangue mineral. Zeta potential measurements of bastnäsite determined the isoelectric point of bastnäsite to occur at approximately pH 6.3 (via electrophoretic measurement) and pH 8.1 (via electroacoustic measurement). Sodium oleate and Flotinor SM15 (a commercial phosphoric acid ester) are both shown to chemically adsorb onto the bastnäsite surface. Zeta potential measurements of bastnäsite with benzohydroxamic acid indicate significant adsorption, especially from pH 5 to pH 10. The microflotation results show that all three collectors were able to successfully recover bastnäsite. SM15 is the least selective collector as it floats both quartz and bastnäsite whereas benzohydroxamic acid is able to selectively float bastnäsite at pH 9. The recovery of bastnäsite using benzohydroxamic acid is also shown to be highly dependent on frother selection. The optimum pH of flotation for all three collectors occurs at pH 9.     

Biotoxicity assessment and lignocellulosic structural changes of phosphoric acid pre-treated young coconut husk hydrolysate for biohydrogen production

Major sugar constituents in young coconut husk were found to be glucans (0.30 g/g husk), while xylans were 0.10 g/g husk. Pre-treatments were carried out using phosphoric acid with dried coconut husk powder under steam heating. The effect of phosphoric acid on coconut husk hydrolysis was observed using acid concentrations of 0%, 1%, 5% and 10% (v/v). Soluble sugar concentration in hydrolysate was increasing proportional to acid concentration, as the total recovered solid decreases. FTIR and XRD analysis showed that acid hydrolysis led to the disruption of internal chemical bonds, causing coconut husk structural sugars to be released into the hydrolysate. Highest soluble sugar concentration, 29.9 g/L with a total suspended solid of 75.1 g/L, was obtained when the coconut husk was pre-treated with 10% phosphoric acid, and can be utilised for biohydrogen fermentation. Biotoxicity testing of the hydrolysates shows that half-maximal inhibition concentration of phosphoric acid was around 4.41% for a 24-h incubation and 3.80% for a 96-h incubation.     

Performance analysis and impedance spectral signatures of high temperature PBI–phosphoric acid gel membrane fuel cells

Polarization curves, i.e., dc performance, and impedance spectral signatures of polybenzimidazole (PBI)–phosphoric acid (H₃PO₄) membrane fuel cells are obtained in the temperature range of 160–180 °C, in an effort to investigate the effect of temperature, anode humidification, various cathode stoichs, and use of oxygen versus air. Thus, in situ electrochemical impedance spectroscopy (EIS) was used to obtain various resistances, ohmic as well as charge-transfer resistances, under these conditions. The results obtained show that PBI–H₃PO₄ gel membrane fuel cells exhibit very good performance in the temperature range of 160–180 °C with an ohmic resistance similar to Nafion. Mass transfer limitations were determined by comparing performance polarization curves with air and oxygen along with EIS. Further EIS was also used to obtain signatures during fuel starvation, and electrical shorting across the cell.     

食品级磷酸中铁含量测定方法研究

火焰原子吸收法测定元素受基体和背景以及黏稠度的影响很大,本文研究采用火焰原子吸收法测定食品级磷酸中铁的含量,并进行了精密度、准确度和检出限的测定试验,以及与工业磷酸中铁含量的测定方法和电感耦合等离子体发射光谱法比对。铁的方法线性良好,相关系数为r=0．9992;精密度高,相对标准偏差为2．75％;准确度高,回收率在95％～105％之间。试验结果表明,该法能够快速、准确地测定磷酸中铁含量,结果令人满意。     

石灰沉淀—活性炭吸附处理汽车涂装磷化废水

针对盐城某汽车涂装车间所产生的磷化废水,采用石灰作为混凝剂,聚丙烯酰胺作为助凝剂对其进行处理,分别进行了石灰、PAM投加量和pH值对除P的影响以及活性炭投加量对CODcr和镍、锌去除率的影响实验。结果表明,石灰最佳投加量为800 mg/L,PAM最佳投加量为5 mg/L,最理想的pH范围在10～11之间,活性炭对废水中的重金属离子的吸附性能良好,此时CODcr的去除率达到83.1%,出水水质达到《污水综合排放标准》（GB 8978-1996）一级排放标准。     

海底磷钙土湿法制备磷酸的研究

海底磷钙土储量丰富,是陆上磷矿石的潜在替代品,为了综合利用海洋资源,对其的深入研究具有重要意义。CLD04样品(海底磷钙土)的反应活性为99 90%,抗阻缓系数为-0 76,其反应性比陆地磷灰石好;以CLD04样品为原料湿法制备磷酸的工艺条件试验表明,在反应温度为65±2℃、反应时间为6 5h、液固比为2 5∶1、搅拌转速为350r/min、成品粗磷酸浓度为25%～28 0%、H2SO4过量3 0%条件下,CLD04样品的分解率、P2O5转化率、P2O5回收率及磷石膏的结晶粒度和形态较为理想。     

KA-01和硫脲TU在磷酸中的缓蚀作用

缓蚀剂KA-01是室内合成的有机缓蚀剂。本文通过静态腐蚀试验和电化学测量对缓蚀剂KA-0l和硫脲(TU)及复配物在15％和28％磷酸中对A3钢的缓蚀性能进行评价,结果表明KA-01和硫脲在30℃和90℃15％和28%磷酸中单独使用具有较好的缓蚀作用,而二者复配使用其缓蚀效果明显增加,在90℃15％和28%磷酸中加入1．8％KA-0l和0．2%TU时A3钢的腐蚀速度低于1g／m^2．h,缓蚀率高达99．8%以上,电化学测量结果表明KA-01和TU是以阴极控制为主的缓蚀剂,而二者的复配物则表现出阴阳极混合控制的特征。     

牙质粘接剂与含Pheny1-P磷化预处理剂结合的功效

α-甲基丙烯酰氧乙基苯基磷酰氯或α－甲基丙烯酰氧乙基苯基磷酸酯（Pheny1-P）是在苯环位置具有取代基团的新功能单体。对于粘接剂的组成，在使用情况下，证明对于牙齿粘接是良好的。牛牙与这些含磷的甲基丙烯酸酯之间已经评价，对于牙本质的粘接强度取决于取代基团，而对珐琅无粘接。     

高质量氧化铝模板的制备及其研究

以5%磷酸为电解液,通过阳极氧化高纯铝片制得了有序性较高的多孔氧化铝模板,结合扫描电镜(SEM)对其结构和行貌进形观察和表征.研究了氧化铝模板的制备工艺,还讨论了氧化铝膜的形成过程,最后比较了一次阳极氧化和二次阳极氧化获得的样品的多孔结构,认为低温下采用二次阳极氧化法可以获得很好的多孔氧化铝模板.     

Characterization of chemosynthetic H3PO4–Al2O3–2SiO2 geopolymers

Pure chemosynthetic Al₂O₃–2SiO₂ powders fabricated by a sol–gel method exhibit high phosphoric acid-activated properties and high compressive strengths. The phosphoric acid-activated properties could be characterized by compressive strength. The phase structure evolution of synthetic powders and the resulting geopolymers were investigated by DTA-TG, XRD, FTIR and MAS NMR analysis. These results show that the phosphoric acid-activation region of the synthetic powders was in the range of 200–800 °C, which was much lower than the temperature at which kaolinite was converted into metakaolinite. ³¹P MAS NMR analysis revealed that [PO₄] tetrahedra were part of the geopolymer structure.