Studies On The Water Purification Material Prepared By A Hydrolysis Of Aluminum Nano Powders And Its Applications In Micro-polluted Water Treatment

The problem of environmental pollution and ecological threats to human health has become widespread concern. It has environmental , economical and social signifecance to adopt a simple and effective way to remove the pollutants in water. Heavy mentals, one of various pollutants in the natural water environment, become an important category of pollutant because of its non-degradation, bio-accumulative effect and greater toxic characteristics at lower concentrations. The traditional methods of removing heavy metals are the chemical precipitation, ion exchange and membrane treatment, but people have encountered a new problem in the purification of drinking water because of complicated polluntants and the increasing types of harmful substances in the contaminated water. The purification materials and technology have been researched a lot at home and abroad. The process technology mainly removes the turbidity, suspended solids, colloid, color and microorganisms, so the ability to remove the organic matter, especially, the dissolved organic matter in water is low (20 percent to 30 percent), and moreover, the wastewater after removal of the heavy metals with low concentration can hardly meet the water quality criterion for drinking. In 2006, China promulgated a new "The Living Drinking Water Standard " GB 5749-2006 which replaced the original standard of GB 5749-85. In the new standard, the number of the tested water-quality items increases from the original 35 to 106 and toxicology indicators of inorganic compounds increase from 10 to 22. The higher requirements are proposed in water quality for the emission limits of arsenic, lead, cadmium and other heavy metals are increased. In the process of conventional wasterwater treatment, aluminum, iron, manganese oxides and hydroxides have the stronger ability to adsorb heavy metals, organic matter, bacteria and viruses in water because they have a larger surface area, a good porous structure and high charged density. The adsorbents which contain aforementioned metal elements are used to treat contamination in the environment, which has attracted more and more interest of science researchers. Nano-materials have the small size effect, surface and interfacial effect, quantum size effect and macroscopic quantum tunnel effect, which enables nano-materials to have the absolute superiority compared with other materials. Nano-materials have high surface activity, high surface energy and large surface areas due to the surface effect. Therefore, nano-materials display the huge potential in the preparation of high-capacity adsorbent. Many kinds of methods, such as chemical vapor deposition, colloidal micellear process, hydrothermal process and hydrolysis methods are used for the synthesis of nanostructure materials. In the above synthetic methods, hydrolyzing nanometer aluminum powders in water is a simple and fast synthesis procedure to produce an aluminum hydroxide fiber with a high specific surface area. Nano-aluminum material is widely used in chinaware, catalyst carrier, catalyst and environment pollution treatment. At present, the researches on application of nanometer fibers prepared by hydrolysis of aluminum nano powders which are prepared by wire electric explosion method to wastewater treatment are still less. So the research of this paper has theoretical and practical significance for the study on the technologies of the environmental wasterwater treatment and the development of materials science.Aluminum nanometer powders were prepared by wire electric explosion method with the equipments in our lab. The technical conditions of electric explosion, the wire explosion parameter and physical mechanism were studied. Simultaneously, the aluminum nano powders were characterised. The result found that the experimental conditions had an effect on the powder's size. The bigger the diameter of metal wire was, the higher the pressure of the medium gas is, the greater the size of the powders was. The energy loaded on the aluminum wire has some impact on the granularity of powders. The concentration of the metallic steam was lower and the granularity of aluminum particles was small when the K was1.5. Meanwhile, the physical mechanism of the process of wire electric explosion: was discussed, namely, "metal wire-melting wires (liquid)-colloid (liquid phase and a metal bubbles)- aerosol-condensation forming metal powder."The nano AlN/Al powders prepared by wire electric explosion method at the nitrogen atmosphere were immersed into deionized water to react with deionized water, thus nano-fibrillar alumina oxyhydroxides were formed in the temperature 40-80℃. The reaction behavior of AlN/Al with water yielded the following results. The boehmite was dominant at a high temperature and low pH, while the bayerite phase became dominant at a low temperature and high pH. The hydrolysis products with the highest specific surface area 267m2 /g came into being at 70℃in the alkaline solution and showed a nano fibrous shape with several nm in diameter and several hundreds nm in length . The hydrolysis reaction was accelerated with the additive salicylate agent. The specific surface areas of hydrolysis products were enlarged from 136.68m2/g to 230.11 m2/g when 0.08 percent of the salicylate sodium was added. the study of sodium salicylate to join the 0.04-0.08 percent suitable. During crystallized process the variation of the hydrolysis product had several stages, which was conduced by the crystal growth, agglomeration, the second nucleus and milling. On the basis of datum, confirm the first production-bayerite decompound to form supersaturation aqua, then the crystallized process was excitated. Along with reaction time went, the crystals become stable and the crystalline raise consumedly.In this paper, the nano-AlO(OH) particles with high surface area prepared by the hydrolysis as an adsorbent for removing copper and lead ions from synthetic solutions were investigated in a batch system. The influential factors, such as adsorbents dose, pH values, salt concentration, contact time, etc. were studied. The adsorption mechanism, thermodynamics and kinetics of adsorptive process were investigated also. The results showed that AlO(OH) could adsorb certain quantity of Cu²⁺ and Pb²⁺. The initial pH value of the solution and salt ions have impact on adsorption of Cu²⁺ and Pb²⁺ on the surface of AlO(OH) particles. Binding of Cu²⁺ and Pb²⁺ ions onto adsorbents was highly pH dependent. The adsorptive quantity of Pb²⁺ was higher than that of Cu²⁺ adsorbed on the surface of AlO(OH) particles. The adsorption of metal ions was partly influenced by the existence of conventional ions in solution. The effect of adsorptive quantity of Cu²⁺ and Pb²⁺ on the AlO(OH) by the existence of Mg²⁺ was greater than that by the presence of Na+. Through the analysis of adsorption isotherms of adsorption of Cu²⁺ and Pb²⁺ onto the AlO(OH), adsorption behavior of Cu²⁺ and Pb²⁺ on the AlO(OH) could be approximately described with the Freundlich equations in the studies of static adsorption. The pseudo-second-order model was the best choice among all the kinetic models to describe the adsorption behavior of Cu²⁺ and Pb²⁺ on the AlO(OH).A novel composite water purifying material, nanometer AlO(OH) loaded on the fiberglass with activated carbon fibers felt(ACF) as the carrier, was prepared by hydrolytic reaction for the removal of Cd²⁺, Mn²⁺, phenol and bacteria from aqueous solution using column adsorption experiment because it is difficult to separate powder absorbents from the water. The influential factors, such as the initial metal ions concentration, pH value and coexisting metal ions, etc. were studied. The studies found that compared with minicrystal cellulose and polyethylene fiber, glass fiber as the carrier of the nano-AlO(OH) particles had better removal ability. Meanwhile further experimental results showed that the ACF carrier was an assistant in the adsorption Cd²⁺ process. The experiment conditions, such as the initial pH, initial Cd²⁺ concentration and the coexisting Pb²⁺ ions have mainly impact on the absorption capability of the novel composite water-purifying material. The results indicated that the relationship between adsorption capacity of Cd²⁺ and pH was not linear, and the maximum adsorption capacity was existed when pH was 6.5. The main adsorption power was exerted due to the different concentrations of Cd²⁺ in sorbent and that in solution, so the adsorption capacity increased and reduced when Cd²⁺ initial concentration was less than 0.068 mg/L and greater than 0.068 mg/L, respectively. The maximum adsorption capacity was exerted in the concentration of 0.068 mg/L. The adsorption ability of the composite water purifying material on Cd²⁺ obviously reduced from 128.5 mg/g to 64.28 mg/g when Pb²⁺ existed because Pb²⁺ took up more adsorption sites. The removal of Mn²⁺ by the water purifying material was also studied. The results indicated that the maximum adsorption capacity of Mn²⁺ was 283.76 mg/g. The adsorptions of metal ions on the composite water-purifying material in aqueous solution were also studied with the fixed-bed column. Thomas equation obtained with the non-linear analysis could describe the adsorption data better than that with the linear analysis. The experiment results indicated that the properties of the new composite water-purifying material was excellent. The adsorbed Cd²⁺ was easily desorbed from the material with 0.1M HCl solution. Adsorption-desorption cycles showed the feasibility of repeated uses of the composited material. Although the removal efficiency of phenol was maintained above 55% when the initial concentration of phenol was 5mg/L, the concentration of the effluent was not steady and the new composite water-purifying material has the disadvantage of short duration. All of those mean the new composite water-purifying material should be amended and its water purifying ability should be optimized. The removal efficiency of the material on bacteria was 68%-97%, and the total bacteria in the effluent were meeting "The Living Drinking Water Standard " GB 5749-2006, which showed that the composite water purifying material for the removal of bacteria had a certain effect. SEM/EDAX and XPS analyses were empolyed to examine the process and mechanism of adsorption on the new composite water-purifying material. The results indicated that the cadmium element evenly scattered on the surface AlO(OH) particles and Cd²⁺ coordinated with oxygen atoms of hydroxyl groups on the AlO(OH) in coordination bond.