Treatment On Thallium (Tl), Arsenic (As) Wastewater By Using ECS And Adsorption Of Microporous Materials

In the scale process of heavy metal ion wastewater treatment applications,adsorption method is simple, suitable for the deep purification of medium and lowconcentration of heavy metal waste water, the materials （adsorbent） adsorptionperformance （adsorption capacity, adsorption rate, capture rate and price/performanceratio） is the key factor restricting their application. The material with a porousstructure, high surface area and abundant surface functional groups is excellentadsorption material for heavy metal ions, including the nanostructured materials withmost abundant surface active groups, especially the ordered nanostructured materials,it can significantly increase the specific surface area of the material which has beenthe focus research as adsorbent. Diatomite is a natural mineral material which maincomponets is amorphous silicon with porous structure, good chemical stability andadsorption abilities. The electrolysis activation pretreatment of wastewater treatmentis the best way to improve the efficiency of heavy metal ion adsorption.Diatomite composite adsorbent was fabricated by coprecipitation methodthrough the introduction of sodium aluminate sol which was deposited on the surfaceof diatomite as the substance, its specific surface area was increased to100m²/g from22m²/g of the original soil. The thallium （Tl） wastewater was deep purified withcombined process of this adsorbent and the electrochemical process. The bestconditions are as follows: electrolytic activation conditions （the current is5A, thevoltage is50V, the pH value of electrolyte is4.5and the electrolysis time is8min）,the adsorption conditions （the pH value of supernatant is8.5, the adsorbent dosage is0.6mg/L, the adsorption time is30minutes and the system stirring speed is110r/min）. The results show that Tl metal ion concentration could be reduced to0.001mg/L（1ppb） from9.45mg/L（9.45ppm） with the best process of two electrolyticactivation and third adsorption purification, the removal rate is up to99.98%.α-Fe₂O₃nanowires/diatomite samples was prepared by thesubsidence-sedimentation method using FeCl₃as the iron source,（（NH₂）₂CO） asprecipitant and used for the As （Ⅲ）, As （Ⅴ） adsorption study. It showed that theformation of the hematite α-Fe₂O₃nanowire crystals were on the surface of diatomitewith the diameter of about10to15nm, the length of250to300nm and the specificsurface area was140m²/g with8wt%FeCl₃aqueous solution at pH4.5and40℃for 35h. The As （Ⅲ）, As （Ⅴ） adsorption results showed that the adsorbent dosage,adsorption time, adsorption temperature are the important factors and pH value, As（Ⅲ）, As （Ⅴ） initial concentration are the key factors for the removal rate of As（Ⅲ）and As（Ⅴ）, respectively. At pH3.5and the As（Ⅲ） or As（Ⅴ） concentration of10mg/L,the maximal efficiency was99.98and100%for the removal of As（Ⅲ） and As（Ⅴ）,respectively. its maximal adsorption capacity of As（Ⅲ） and As（Ⅴ） were60.65and81.16mg/g, respectively.The diatomite sodium-based zeolite and α-Fe₂O₃nanowires/diatomite sampleswere characterized by means of the techniques, such as X-ray diffraction, scanningelectron microscopy, transmission electron microscopy, Brunauer-Emmett-Tellermeasurement and so on, we used Fourier Transform Infrared Spectroscopy and X-rayphotoelectron spectroscopy techniques to characterize the prepared samples beforeand after the adsorption of As （Ⅲ）, As （Ⅴ）, it showed the adsorption mechanism ofarsenic were early mainly for physical adsorption by electrostatic attraction and latefor chemical adsorption by combining valence bond.