The production of phosphoric acid from natural phosphate rock by means of the wet process gives rise to an industrial by-product named phosphogypsum (PG). About 5 tonnes of PG are generated per tonne of phosphoric acid production, and worldwide PG generation is estimated to be around 100-280 Mt per year. Most of this by-product is disposed of without any treatment, usually by dumping in large stockpiles. These are generally located in coastal areas close to phosphoric acid plants, where they occupy large land areas and cause serious environmental damage. PG is mainly composed of gypsum but also contains a high level of impurities such as phosphates, fluorides and sulphates, naturally occurring radionuclides, heavy metals, and other trace elements. All of this adds up to a negative environmental impact and many restrictions on PG applications. Up to 15% of world PG production is used to make building materials, as a soil amendment and as a set controller in the manufacture of Portland cement; uses that have been banned in most countries. The USEPA has classified PG as a "Technologically Enhanced Naturally Occurring Radioactive Material" (TENORM).This work reviews the different environmental impacts associated with PG storage and disposal. The methods described in the literature to minimise the negative effects of this waste are classified by treatment type, i.e. physical, chemical, thermal, etc., and different suggested applications for PG are detailed.

The Interactions of low density llpoproteln (LDL) and apollpoproteln (apo) B-100 segments with chondroltin-6-S0 4 rich aortic proteoglycans aggregate (CSPG) were studied by using quantitative frontal elutlon affinity chromatography. The affinity of the agarose-CSPG was higher for LDL than for very low density llpoproteln, and high density llpoproteln was not bound. LDL from different Individuals had dissociation coefficients (Kd) from 28 to 179 nM. Experiments with tryptlc hydrolysates of apo B suggested that the capacity of LDL to bind with CSPG resides in the protein. Nine apo B-100 hydrophlllc peptldes, 12 to 26 amlno acids long, were selected, and three were found to Interact with the agarose-bound CSPG: apo B P-1 (LRKHKUDVISMY-RELLKDLSKEA, residues 4230 to 4254), apo B P-2 (RLTRKRGLKLATALSLSNK, residues 3359 to 3377), and apo B P-11 (RQVSHAKEKLTALTKK, residues 2106 to 2121). These peptides competed with LDL for binding to the agarose-bound and soluble CSPG; apo B P-2 was the most effective. This correlates with Kd values: 63, 86, and 82 /iM for apo B P-2, P-1, and P-11, respectively. The peptldes shared an excess of positive-charged side chains. Apo B P-2 belongs to the lys-and arg-rich, LDL-receptor domain. Apo E also binds to the agarose-proteoglycan. The results suggest that apo B regions with sequences and charge distributions analogous to those of residues 3359 to 3377, 4230 to 4254, and 2106 to 2121 are among those responsible for the Interaction of LDL with Intlma-media CSPG. (Arteriosclerosis 8:368-377, July/August 1988)

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The reversible interaction of low density lipoprotein (LDL) with arterial chondroitin sulfate proteoglycans (CSPGs) or glycosaminoglycans (GAGs) selects LDL particles with a high affinity for sulfated GAGs and also induces modifications in apolipoprotein B (apo B) and the lipid organization of the lipoprotein. In the present work we studied the effect that the reversible interaction with sulfated polysaccharides has on the susceptibility of LDL to in vitro oxidation. For this purpose soluble, nonaggregated CSPG-or GAG-treated LDL was subjected to oxidation in the presence of 5 fiM CuSO 4 for as long as 48 hours. The rate of formation of thiobarbituric acid-reactive substances, the decrease in isoelectric point, the increase in relative electrophoretic mobility of LDL, the higher degradation rate by human macrophages, and the lower degradation rate by human arterial smooth muscle cells showed that LDLs exposed to CSPGs and GAGs were significantly more susceptible to oxidation than native LDL. Results from competition experiments indicate that C6S-treated LDL after 4 hours of oxidation is taken up via the acetylated LDL receptor in human macrophages. Coincubation of lipoproteins with human macrophages or human arterial smooth muscle cells for 24 hours also indicated that C6S-treated LDL was more susceptible to cell-induced modifications than native LDL. The occurrence in vivo of similar processes may contribute to focal retention, increased rate oxidation of LDL in the arterial intima, and foam cell formation during atherogenesis. ( 11 The interaction of low density lipoprotein (LDL) with human arterial chondroitin sulfate proteoglycans (CSPGs) or glycosaminoglycans (GAGs) induces changes in the apo B lipoprotein and lipid organization that can be observed by

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A study was made of the copper corrosion rate and corrosion products originated by the action of acetic acid vapor at 100% relative humidity. Copper plates were exposed to an acetic acid contaminated atmosphere for a period of 21 days. Five acetic vapor concentration levels were used. The copper corrosion rate was in the range of 1 to 23 mg/din2 day. The corrosion-product layers were characterized using electrochemical, X-ray powder diffraction, Fourier transform infrared spectrometry, and scanning electron microscopy techniques. Thermal and calorimetric studies were also performed. Some of the compounds identified were cuprite (Cu,O), copper acetate hydrate [Cu(CH,COO)22H,O], and copper hydroxide acetate [Cu4(OH)(CH,COO)72H20]. This last compound was also characterized. The thickness of the patina layers was 4 to 8 nm for amorphous cuprite, 11 to 48 nm for cuprite, and 225 nm for copper acetate. The patina, in which the cementation process of different corrosion-product layers plays an important role, is formed by the reaction of acetic vapor with copper through porous cuprite paths.

This work reports the preparation of activated carbons via the hydrothermal treatment at 523 K/30 bar of two common winemaking wastes: bagasse and cluster stalks. The hydrothermal carbons produced by the above treatment were turned into activated carbons via their exposure to KOH and carbonization at 1073 K. These were then subjected to Raman spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy examination, and the determination of their Brunauer-Emmett-Teller surface area. The ability of the activated carbons to adsorb methylene blue in aqueous solution was then examined, determining the influence of time, methylene blue concentration, and temperature. Equilibrium conditions were reached for reaction times between 180 and 240 min at pH 7. The adsorption isotherms were found to better fit the Langmuir than the Freundlich model, and the adsorption kinetics fitted a pseudo-second-order model. The maximum adsorption at 303 K was 714-847 mg g À1. Thermodynamic studies revealed the adsorption of methylene blue to be spontaneous and exothermic. These results show that high-quality activated carbons can be produced from winemaking waste.