铅化法生产草酸中含铅废水的治理

本文阐述了铅化法草酸所排放的含铅废水污染环境严重 ,必须治理。从理论分析入手 ,经过小试探索找出二步化学法处理该污水 ,并在工业生产中得到了应用 ,获得了良好的效果。

High temperature oxidation resistance and microstructure change of aluminized coating on copper substrate

The outermost coating with single phase Ni2Al3 was obtained on copper surface by electrodepositing nickel followed by slurry pack aluminizing at 800 °C for 12 h. The oxidation resistance and microstructure of the coating oxidized in ambient air at 1000 °C for 25-250 h were investigated using SEM, X-ray diffraction and optical microscope methods. The results show that the copper with single phase Ni2Al3 coating possesses the best high temperature oxidation resistance, and the mass gain of the coating is 1/15 that of pure copper and 1/2 that of nickel coating, respectively. The specimen surface after being oxidized for 25 h still comprises Ni2Al3 phase. However, when the time of oxidizing treatment increases to 50 h, the Ni Al phase is formed. It is also found that the Ni2Al3 phase completely turns into Ni Al phase after oxidizing treatment for 100 h and above. The Ni Al coating shows excellent high temperature oxidation resistance when oxidation time is 250 h.

Vapor pressure measurement of lead and lead chlorides in FeO_T-CaO-SiO_2-Al_2O_3 system

Vapor pressure of lead and lead chlorides from FeOT？CaO？SiO2？Al2O3 slag system was measured by using Knudsen effusion method. The results suggest that the vapor pressures of lead and lead chlorides increase with increasing temperature. For the slag systems without chlorine, the logarithm of vapor pressure （lnp） shows highly linear dependency on the reciprocal of temperature （1/T）, and higher vapor pressure is observed in the condition where more metallic lead vapor is formed. In this case, the vapor pressure of lead increases with increasing slag basicity （w（CaO）/w（SiO2））, increasing FeO content andw（Fe2＋）/w（Fe3＋） ratio. For the case of slag system with chlorine addition, the total pressures of PbCl2 and PbCl increase with decreasing basicity and FeO content of slag.

THE PREPARATION AND PHOTOCATALYTIC ABILITY OF LEAD TITANATE

he perovskite-type PbTiO3 has been synthesized by the method of mixed oxides. The appropriate conditions for preparing have been reported. The obtained PbTiO3 powder is pure and fine. The decolorization of dyes in a PbTiO3 suspension system is over 90%. In this paper the photocatalytic ability of PbTiO3 and the factors of influence are discussed.

Preparation of elemental As from As-Sb fly ash using continuous reductive method with additive of lead oxide

To recycle arsenic from an As-Sb fly ash,a newly continuous reductive method for obtaining elemental As with additive of PbO was proposed.In the first reduction stage,PbO promoted the As segregation from the As-Sb fly ash,due to which most As volatilized and Sb retained in roasted residues in phases of As-Sb-Pb-O and As-Sb-Pb alloy.With the increase of PbO and reductant amounts,the Sb fixation rate increased in the first reduction stage,and further the Sb content in the elemental As obtained from the second reduction stage decreased.After being roasted for 30 min at 550℃ with the addition of 20%activated carbon and 12%PbO in the first reduction stage,the As volatilization rate and Sb fixation rate from the As-Sb fly ash reached 92.86%and 79.38%,respectively.Then through the second reduction of the volatile matters at 650℃,the As and Sb contents in the obtained elemental As reached 99.07 wt%and 0.22 wt%respectively,indicating that the obtained As could be used to prepare high purity As,thereby rendering the As-Sb fly ash recycling.

High precision in-situ Pb isotopic analysis of sulfide minerals by femtosecond laser ablation multi-collector inductively coupled plasma mass spectrometry

An in-situ microanalysis of Pb isotopic compositions in sulfide minerals is carried out by using femtosecond laser-ablation multi-collector inductively coupled plasma mass spectrometry （fsLA-MC-ICP-MS）. High-temperature-activated carbon was used to filter Hg contained in the carrier gas, which reduced the Hg background signal by 48% and also lowered the detection limit of the analysis. Fractionation and mass discrimination effects existing in the ICP-MS analytical processes were corrected using an internal reference T1 in conjunction with an external reference NIST SRM 610. The proposed method was used to an- alyze the Pb isotopic compositions of chalcopyrite, pyrite, and sphalerite from the Dulong Sn-Zn-In polymetallic ore district. The results showed that in this ore district, the sulfide minerals and different grains of the same sulfide mineral show a large variation in Pb content up to 1000-fold. The studied pyrites show relatively higher Pb contents and homogeneous Pb isotopic compositions, whereas the sphalerites have low Pb contents but most variable Pb isotopic compositions. It is suggested that the large variation of Pb isotopic composition may reflect a late hydrothermal superimposition on the primary sulfide formation. In addition, radiogenic Pb accumulated by radioactive decay of trace amounts of U over time in the host minerals may also be one of the causes for the large variation range of Pb content and Pb isotopic composition of those low-Pb sphalerites. Chalcopyrite and sphalerite grains with Pb content greater than 10 ppm presented a consistent Pb isotopic distribution, whereas all the sulfide grains with Pb content greater than 100 ppm had consistent Pb isotopic composition within 2s measurement uncertainties. The in-situ analysis of Pb isotopic composition agreed well with the results obtained by conventional chemical methods within 2s measurement uncertainties, indicating that the data obtained by fsLA-MC-ICP-MS are reliable. Additionally, this study indicates that the Pb isotopic composition could truthfully record the source of ore-forming minerals only for sulfide minerals with high Pb content. On the contrary, the Pb isotopic composition of low-Pb sulfide minerals may be affected by trace amounts of U in the host minerals that may lead to a highly radiogenic Pb isotope ratio. Alternatively, it is also possible that late fluid metasomatic overprinting may alter the Pb isotopic compositions.