Effects Of Purifying Water Through A Novel Nano-Al₂O₃ Material: A Preliminary Investigation

Water is the essential matter to maintain the human living. Thesources of drinking water are getting worse because of the graduallyserious pollution of environment. The concentrations of heavy metalsand organic matters are greater than the limit concentration in manyareas, which give a bad effect on human beings. Because the kinds ofthe nocuous matters, which can be examined in water, are increasegradually, the conventional technology "coagulation – precipitation –filtration -chlorine disinfection" meets the challenge from newtechnologies. It is hard for conventional technologies to remove thesoluble micro-organic matters in the drinking water source, and thereare many kinds of organic chlorides including "Three Causing"(causing abnormality, causing mutation, and causing cancer) thatproduce during the process of the chlorine disinfection. In order to gethealthy drinking water and deep decontaminate water supply, manycountries adopt lots of technologies such as ozone oxygen, activecarbon adsorption, photocatalyst, reverse permeation, and membraneseparation. Membrane technology has gain extensive concerns.Membrane technology includes ultra-filtration, micro-filtration andnano-filtration. Membrane technology is widely applied more andmore in our country. Compared with ultra-filtration andmicro-filtration, the removal of Fe, Mn, organic matters and coliformusing nano-filtration technology got a good purpose, that because thepore diameter and surface characters of the nano-filtration membranegive a special capacity to itself. This technology has the followingadvantages: it can intercept the organic matters whose molecularweight are more than 200, and the multivalence ions, partially removethe matters whose molecular weight are less than 200 and univalenceions, enduring pollution, low processing pressure, saving energy, highmembrane flux, inexpensive cost, no membrane pollution.Nano-material has the small size effect, surface and interfacialeffect, quantum size effect and macroscopic quantum tunnel effect,which enables it the absolute superiority comparing with othermaterials. Nano-material has widely used in the fields of chinaware,catalyst, biology and medical since 1990s. At present, nano-materialsare gradually applies to the field of environmental protection, theapplications to water treatment include the following three aspects: (1)Remove the pollutants in the water as catalyst, such as TiO2, CdS. (2)nano-filtration membrane technology. (3) Water treatment medicine,which could remove the pollutant in the water directly.Nano-material has high surface activity, high surface energy andlarge surface areas due to the surface effect. Therefore, nano materialsdisplay the huge potential in the preparation high capacity adsorbent.Nano-aluminum oxide material, which was used in this paper, is onekind of nano-filtration membrane. Nano-aluminum oxide material iswidely used in chinaware, catalyst carrier, catalyst, and micro-filtration.At present, the research on application of nano-aluminum oxidematerial in water treatment is still less. The improvement of thematerial will be achieved on the basis of the right assessment to thematerial capacity. Therefore, Cd, Mn, 2, 4-Dichlorophenol and thetotal amount bacteria were selected as the representations of thegeneral chemistry index, the toxicity index, and bacteriology index,which are stated in the . Theresearch of this paper is helpful to guide the preparation andamendment of the material.In this paper, the appearance of nanometer Al2O3/Carbon materialwas measured through SEM and TEM, and the surface area, porediameter and pore volumes were measured by BET Nitrogenadsorption technique. The results showed that the material possesseshuge surface area(431.74 m2/g), nanometer grade pore size (themaximum is 51 nm), the smaller the particle size. Considerableresearches have proved that the particle size of the adsorbent is a mainfactor that determines the adsorption ability. Hence thenano-aluminum oxide material with huge surface area must haveenormous superiority in adsorption ability.Cadmium, as one of the principle toxic heavy metals among thosecontainments responsible for causing environmental problems andhuman health, is strictly controlled in drinking water. So it wasselected to be the main research object in this paper, and the adsorptionability of material on Cd and the factors that affect the adsorptionability were studied. The results indicated that the maximumadsorption capacity was 246.9 mg/g using Thomas model. Comparedwith other adsorbents, the maximum adsorption of nano-aluminumoxide material is almost 1-2 magnitude greater than that of others.Factors affecting adsorption of Cd to nano-aluminum oxidematerial not only include pH, the initial concentration, and coexistingions, but also include the characteristics of the materials. The studiesfound that compared with minicrystal cellulose and polyethylene fiber,activated carbon fiber as the carrier of the nano-aluminum oxideparticles had better removal ability, and the carrier was an assistant inthe adsorption process. The results indicated that the relationshipbetween adsorption capacity of Cd and pH was not linear, and themaximum adsorption capacity was existed when pH was 7.0. The mainadsorption power was the difference between Cd concentration insorbent and that in solution, so the adsorption capacity increased andreduced when Cd initial concentration was less than 0.10 mg/l andgreater than 0.10 mg/l, respectively, and the maximum adsorptioncapacity was in the concentration of 0.10 mg/l. The adsorption ability ofnano-aluminum oxide material on Cd obviously reduced from 246.9mg/g to 85.70 mg/g when Pb existed which was due to Pb took up moreadsorption sites.The removal of Mn, 2, 4-Dichlorophenol and bacteria were alsostudied. The results indicated that the maximum adsorption capacity ofMn was 246.9 mg/g using Thomas model. Although the removalefficiency of 2, 4-Dichlorophenol was maintained above 50% during 3h, the quality of effluent was not steady. The removal efficiency ofmaterial on bacteria was 80%-99.5%, and the total bacteria in effluentwere meeting the drinking water sanitation standard, but it has thedisadvantage of short duration. All of those mean the nano-aluminumoxide material should be amended and optimize its water purifyingability.