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High energy consumption is characteristic of the industrial production of aluminium. In the , initial, alumina production phase, THERMAL CONSUMPTION is predominant and becomes an important factor in the cost of production when the raw material used is a bauxite with a high diasporic content which, in the instance of existing bauxite reserves on our old continent, is the case. In the, second, aluminium production phase, a high consumption of ELECTRIC ENERGY is predominant. That is why aluminium production is termed an ELECTRICITY HUNGRY INDUSTRY. Successive energy crises therefore forced this industry to reduce, in both phases of production, its energy consumption. Our plant comprises both of these procedures, that is alumina and aluminium production.

Acid deposition is an environmental concern of global importance. One of the major deleterious effects of acid deposition on the lithosphere is aluminium mobilization in the soil environment and consequent aluminium toxicity to terrestrial vegetation and aquatic biota. We applied a sulfuric acid-containing nutrient solution to an artificial plant growth medium which contained Al(OH)3 precipitated on montmorillonite (interlayer-Al(OH)3). We determined pH and total concentrations of Al, Ca, Mg, K, Na, So4, Cl, NO3 and PO4 in leachate solutions and calculated the activity of Al, K, SO4 and other ions with MINTEQA1, a computer speciation program. We found that Al activity was controlled by interlayer-Al(OH)3 when 2pH + pSO4 was less than 12.7, as long as this phase was not depleted. When 2pH + pSO4 was more than 12.7, the Al activity followed a line parallel to crystalline alunite, implying an unknown Al-controlling phase of the same Al/S/K/OH ratio, but more soluble than the crystalline alunite. We propose that this unknown phase is amorphous alunite. The re-examination of several sets of published data for naturally-acidic surface and ground waters, mine waste drainage water, and solutions from acidic soils and sediments revealed that the Al activity in those solutions fell between what would be expected for equilibrium with the proposed amorphous alunite (upper limit) and the crystalline alunite (lower limit). This implies that an alunite-like aluminium sulfate may have controlled Al activity in natural environments that were influenced by sulfate and proton input from either natural or manmade causes.

In the clay fraction of soils, (hydr)oxides of Fe, Al and Mn are common. These hydroxides may differ considerably in particle size, purity, and crystallinity from the ‘model (hydr)oxides’ used frequently in laboratory studies. They may occur as discrete particles, having hardly any contact with the clay surface, and as coatings on, or as interlayers between clay mineral surfaces. Jenne (1968) suggested that the reactivity of hydroxide coatings would be considerably higher than the reactivity of free hydroxides, especially with respect to heavy metal adsorption. Since then, several authors have investigated the effect of the removal of hydroxides from soil clays on heavy metal adsorption, but their results are not unambiguous.

In this chapter, we discuss the use of high doses of CaC03 and other alkaline salts of calcium as well as of magnesium hydroxide and magnesium carbonate as alternative phosphate binders for Al(OH)2.

While using neutron activation analysis for estimating fluoride in uraemic bone we discovered appreciable quantities of aluminium in bone, particularly from patients living in the Newcastle area.(l) This finding was confirmed and linked to an indolent type of fracturing osteomalacia(2) in this area. Other complications include dialysis encephalopathy,(3) uraemic neuropathy,(4) microcytic anaemia,(5) and suppression of parathyroid hormone secretion.(6) Many of these symptoms can be reversed by the use of aluminium free dialysate water(7) and by the administration of desferrioxamine.(8)

Since the report by Ward et al (Wa 78), suggesting that aluminium may be a major factor of bone disease in dialyzed patients, evidence has accumulated in support of this hypothesis. It has been particulary shown that aluminium accumulates in bone of uremic patients, especially at the mineralization front (Co 81), and can induce the development of vitamin D resistant osteomalacia. Most cases of histologically proved osteomalacia have been reported in heavily intoxicated patients, exposed to contaminated dialysis water, presenting with symptoms including fractures and encephalopathy (Pi 80, Ho 82). Beside these well demonstrated cases of florid osteomalacia, due to severe aluminium intoxication, little is known about the bone effects of mild aluminium overload. In this study we evaluated the bone aluminium content and toxicity in uremic patients on chronic hemodialysis or hemofiltration with mild aluminium overload mainly induced by aluminium-containing gels prescribed to control serum phosphate.

There is now no doubt that aluminium contamination of water supplies used for the preparation of dialysis fluid can lead to encephalopathy, vitamin D resistant fracturing osteomalacia and microcytic anaemia in patients receiving haemodialysis. Although the introduction of adequate water treatment to remove aluminium has effectively stopped the epidemics of these diseases which made them the major cause of death in some dialysis units in the 1970’s, sporadic occurrences of identical syndromes have also been described in patients who have never received dialysis, have been trated exclusively with peritoneal dialysis or have received haemodialysis using water known to have a very low aluminium content. In these patients other sources of aluminium have been implicated, the oral administration of aluminium salts used as phosphate-binding agents and contamination of parenteral fluids being the culprits. The rate of aluminium accummulation, which has marked effects on the distribution within the body, has been slower with oral administration. Thus, a new pattern of aluminium-related disease with a different epidemiology is emerging in patients with renal failure. This has ensured that the prevention, detection and treatment of aluminium toxicity will continue to be an important part of nephrological practice for many years.