Recovery of nitric acid from waste etching solution using solvent extraction.
A process was developed to recover nitric acid from the waste stream of wafer industry using solvent extraction technique. Tributyl phosphate (TBP) was selected among several extractants because of its better selectivity towards HNO(3), overall superiority in operation, favorable physical properties and economics. The waste solution containing 260 g/L CH(3)COOH, 460 g/L HNO(3), 113 g/L HF and 19.6g/L Si was used as feed solution for process optimization. In the pre-treatment stage >99% silicon and hydrofluoric acid was precipitated out as Na(2)SiF(6). Equilibrium conditions for HNO(3) recovery were optimized from the batch test results as: four stages of extraction at an organic:aqueous (O:A) ratio of 3, four stages of scrubbing at O:A ratio of 5 and five stages of stripping at an O:A ratio of 1.5. The extraction of HNO(3) was suppressed by the presence of acetic acid (HAc) in the feed solution. To examine the feasibility of the extraction system a continuous operation was carried out for 200 h using a multistage mixer-settler. The concentration of pure HNO(3) recovered was 235 g/L with a purity of 99.8%.
QPPO/PVA anion exchange hybrid membranes from double crosslinking agents for acid recovery
Abstract Hybrid membranes containing both –N + (CH 3 ) 3 Br − and –OH groups are prepared from quaternized poly(2,6-dimethyl-1,4-phenylene oxide) (QPPO) and polyvinyl alcohol (PVA). The QPPO and PVA are crosslinked with double crosslinking agents including monophenyl triethoxysilane (EPh) and tetraethoxysilane (TEOS) through sol–gel process. The double crosslinking agents are effective for the crosslinking in both QPPO and PVA phases. The hybrid membranes contain plenty of micropores but have no obvious silica particles. The membranes have the ion exchange capacities of 1.22–1.92 mmol/g, water uptake of 63–205%, the initial decomposition temperatures of 225–239 °C, and the swelling degrees in 65 °C water of 105–426%. The –OH groups of PVA can be regarded as assistant functional groups for the sorption of HCl and diffusion dialysis (DD) process. As the PVA content increases from 10% to 60%, the sorbed HCl concentration increases from 0.36 mol/L to 2.9 mol/L in HCl solution, while the sorption capacity is generally stable in the mixture of HCl and FeCl 2 . The dialysis coefficient of HCl ( U H ) increases from 0.021 m/h to 0.049 m/h, but the separation factor ( S ) decreases from 39 to 26. When compared with the commercial DF-120 membrane (0.009 m/h, 18.5), the QPPO/PVA hybrid membranes can be potentially applied in DD process for acid recovery.
2000 Review conference of the parties to the treaty on the non-proliferation of Nuclear Weapons, final document
4. The Conference notes that the non-nuclearweapon States Parties to the Treaty reaffirmed their commitment not to receive the transfer from any transferor whatsoever of nuclear weapons or other nuclear explosive devices or of control over such weapons or explosive devices directly, or indirectly, not to manufacture or otherwise acquire nuclear weapons or other nuclear explosive devices, and not to seek or receive any assistance in the manufacture of nuclear weapons or other nuclear explosive devices. 2000 REVIEW CONFERENCE OF THE PARTIES TO THE TREATY ON THE NON-PROLIFERATION OF NUCLEAR WEAPONS FINAL DOCUMENT