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O tratamento de rejeitos de determinados processos industriais vem ganhando importância, seja pelo impacto negativo do simples descarte no meio ambiente, seja pelo valor econômico de materiais e substâncias que podem ser eventualmente recuperados e reciclados. O rápido empobrecimento de reservas minerais primárias e o aumento de demanda de energia são problemas que merecem atenção especial. Neste contexto, a recuperação de metais existentes nos rejeitos de alguns processos de fabricação assume papel de maior importância. A recuperação do molibdênio presente em soluções nitro-sulfúricas, na forma de rejeitos líquidos do processo de fabricação de lâmpadas incandescentes e fluorescentes, não constitui exceção no que diz respeito à importância da reciclagem. Este rejeito, proveniente da dissolução dos mandris de conformação dos filamentos de tungstênio das lâmpadas, apresenta valores que podem ser recuperados e até reciclados no próprio processo. É o caso dos ácidos nítrico e sulfúrico. Já o molibdênio, presente em concentrações em torno de 40 a 90 g.L-1, pode ser recuperado e utilizado na fabricação de aços especiais, pigmentos, lubrificantes, adubo, etc. Neste trabalho foram desenvolvidos dois processos de recuperação deste rejeito. No primeiro, o rejeito é diluído e por cromatografia de troca iônica o molibdênio é recuperado. Os ácidos efluentes são destilados para a retirada da água. No segundo processo, o rejeito passa por uma destilação e ao mesmo tempo o molibdênio é precipitado. Em ambos os processos, os ácidos recuperados podem voltar à fábrica de lâmpadas para a dissolução dos mandris do filamento de tungstênio e o molibdênio encontra outras diferentes aplicações, além de possuir um valor significativo no mercado. / The waste treatment of certain industrial processes is becoming more important, either by the economic impact of simple disposal in the environment, or by the economic value of materials and substances that can eventually be recovered and recycled. The rapid depletion of mineral reserves and increasing primary energy demand are problems that deserve special attention. In this context, the recovery of metals present in waste of some manufacturing processes assumes a great importance. The recovery of molybdenum present in nitro-sulfur solutions in the form of liquid waste in the manufacturing process of incandescent and fluorescent lamps, is no exception with regard to the importance of recycling. The tailing from the dissolution of the molybdenum mandrel wires used in the conformation of the tungsten filament of electric lamps, has values that can be recovered and recycled to the process itself. Is the case of sulfuric and nitric acids. Molybdenum, present in concentrations around 40 to 90 g.L-1, can be recovered and used in the manufacture of special stainless steel, pigments, lubricants, fertilizer, etc.. In this work two processes for the recovery of this waste were proposed. At the first one, the waste is diluted and molybdenum is recovered by ion-exchange chromatography. The effluent acid from this process was distilled to extract water used in the dilution step. In the second case, the waste goes through a distillation while the molybdenum is precipitated. In both cases, the acids are recovered back to the lamp factory for the dissolution of the molybdenum mandrel wires and molybdenum finds other different applications, as well as having significant value in the market.

M.Sc. (Chemistry) / The storage as solid Ag12BI(s) of reactor produced 12BI (t~ = 1.6 x 107 a) in underground respositories can present an environmental problem due to the potential release of radioactive 12BI into the environment over extended storage periods. One process that causes concern is the solubilization of AgI through complexation when brought into contact with underground water, particularly those with high salt content. In this work the charaqterization of the complexation equilibria in the AgI(s)/I-(aq),CI-(aq) system was studied. Solu- I tions containing high CI- and low 1- concentrations were of special interest with regard to the possible formation of ternary complexes. The presence of AgICI22- was indicated experimentally but no evidence of other ternary species like AgI2CI2- or AgIsCIS- could be established. Solubilities were determined radiochemically by using specially prepared 110mAgI. Solubility curves for AgI in different I-/CI- mixtures were adequately explained in terms of models consisting of the species AgCls2-, AgC14S-, AgIs2-, AgI4s- and AgICI22-. Distribution curves were calculated for different I-/CI- mixtures. As an alternative detection mode for silver-determination a flow injection system incorporating a micro-column of activated alumina was used in conjuntion with flame atomic absorption spectrometry for the pre-concentration and determination of silver in water. The procedure was successfully applied to a range of water samples, but no determination of silver in halide or perchlorate media was possible. The limit of detection based on a sample volume of 15 cms was 4.5 ~gdm-3 and the relative standard deviations at 50 and 5 ~gdm-3 were 5.4 and 19%, respectively. In part B of this work a method for the determination of chloride in organic compounds (oils provided by the Atomic Energy Corporation) by using an Parr oxygen bomb and ion chromatography was studied. The combustion products were absorbed in H20. The solution was injected into an ion chromatograph equipped with an anion analytical column, membrane suppressor and conductivity detector. The instrument response was calibrated using different standard solutions. These were prepared from several organic solutions, an organic salt and from sodiumchloride. Calibration curves were linear over a wide range and presented good reproducibility. It differed however according to the type of standard solution used. The limit of detection was 255 ~gdm-3 and the relative standard deviations at 10, 1 and 0.5 ugcm-3 were 0.52, 1.64 and 3.5%, respectively. As an alternative decomposition method wet decomposition within a sealed system (autoclave) was used. Due to the high blank values in this method no analysis of substances could be made in the lower ugcm-3 range.

D.Sc. (Chemistry) / Please refer to full text to view abstract

The problem with which this research is concerned is the determination of inorganic anions and cations with single injection ion chromatography. Direct detection of the separated analyte ions occurs after the analyte ions have passed through ion-exchange resins where they are separated according to their affinity for the ion-exchange resin active sites. The techniques involve the use of essentially a non-suppressed ion chromatographic system followed by a suppressed ion chromatographic system. With this system it is possible to accomplish both qualitative and quantitative determinations.

In our previous studies, uncross-linked large diameter cellulose beads were optimized for solids content, bead size, pressure-flow limits, molecular accessibility and performance as an immunosorbent. Here, anion exchange (DEAE) cellulose beads were derivatized by two different procedures (defined as A and B) and the changes in bead morphology were correlated with transport and sorption kinetics. The kinetic characteristics clearly defined a minimum of two different types of protein binding site architecture. DEAE cellulose beads exhibited molecular exclusion of BSA near the edge of the bead in contrast to greater permeability seen in underivatized beads. Thus, accessible BSA binding sites are present only on the surface of the derivatized beads. DEAE cellulose beads derivatized by procedure B gave higher density of DEAE ligand as compared to beads derivatized by procedure A, as well as higher static and dynamic capacity for BSA. Even though DEAE cellulose beads (DP 2070, 450 μm diameter derivatized by procedure B) have lower small ion capacity than DEAE cross-linked agarose beads, as well as 1/4 the surface area, they exhibit equivalent binding capacity for BSA per volume of support. Thus, DEAE cellulose beads possess more sites per surface area as well as have lower ligand density per BSA site. Furthermore, BSA adsorption sites on DEAE cellulose beads derivatized by procedure B exhibit slow binding kinetics as compared to those derivatized by procedure A and also compared to DEAE crosslinked agarose beads. Thus, the rate limiting step for the adsorption of BSA on DEAE cellulose beads was not diffusion as suggested by the large diameter of the bead. Feasibility studies were performed for process scale applications to fixed and expanded bed anion exchange purification. The large diameter DEAE cellulose beads of this study maybe useful for process scale anion exchange as evident from purification of immunoglobulins from hybridoma cell culture in fixed bed. The balance of large diameter and density of these DEAE cellulose beads enable stable expanded bed purification of proteins such as recombinant human protein C from transgenic porcine whey. / Ph. D.

103Pd is an important therapeutic radionuclide and has recently found great interest due to its higher radiobiologic effect. 109Cd decays by electron capture and is generally used as calibration sources in industrial and medical fields. A new method for the production of 103Pd and 109Cd using the 66 MeV proton beam of iThemba LABS on a tandem natural silver target (Ag/Ag) has been developed. The tandem targets (each target with a mass of 9 g and a thickness of 3 mm) were placed in the high energy slot (62.515 MeV - 40.173 MeV) and low energy slot (38.652 MeV – 0 MeV) to produce the bulk 103Pd and 109Cd, respectively. The radiochemical separation of the Pd radionuclides (103Pd, 100Pd) and the co-produced Rh radioisotopes (mainly 101Rh and 100Rh which are produced from decay of their Pd parents) from the bulk natAg was achieved using a Chelex chelating resin column. In the preliminary studies, different size columns (3 cm x 1 cm, 11 cm x 1 cm, 13 cm x 1 cm and 16 cm x 1.5 cm) were investigated to determine the optimal column conditions for the separation. It was determined that the optimal conditions for the chemical separation was with a 13 cm x 1 cm resin column with the elution of Rh and Ag radionuclides carried out with 1 M HNO3 and the elution of Pd radionuclides with 10 M HCl. No Ag or Rh impurities were detected in the final product and the average recovery of Pd was > 96 %. This work was repeated using a ―hot‖ irradiated Ag target and the chemical processing was done in a hot cell using the same resin column conditions. The recovery of the high purity 103Pd from the irradiated natAg target was found to be > 95 %. The radiochemical separation of 109Cd from the bulk natAg target was done in two parts. In the first part, the precipitation method was used to reduce the silver into a metallic form using 30 g of Cu turnings. The resulting 109Cd filtrate was loaded onto a AG-X10 anion exchange resin column (6 cm x 1 cm). For the optimal chemical separation, the elution of Ag and Cu(II) was carried out with 2 M HCl containing H2O2 and the elution of 109Cd was accomplished with 1 M HNO3. The recovery yield of 109Cd was > 99 %. / Chemistry / M.Sc. (Chemistry)