Dioxon Sorption by Hydroxy-Aluminum-Treated Clays

Abstract

Abstract--The treatment of smectites with a hydroxy-A1 polymer produced chemically modified clays that had much greater affinities for chlorinated dioxins and biphenyls than untreated clays. For hydroxyAl-treated kaolinite, the high affinity for chlorinated dioxins is thought to have arisen from an interaction between the hydroxy-A1 polymer bound to the clay and the chlorinated dioxin in solution. Thus, the adsorption of dioxins from aqueous solution by hydroxy-Al-treated clays is similar to the adsorption of reactants from the gas phase by metals supported on mineral oxides during catalysis. In both systems, the essentially inert mineral oxide support effectively disperses the active adsorptive agent. At the concentrations of octachlorodioxin used in this study (-< 5 ppb), hydroxy-Al-montmorillonite had a distribution coefficient of 90,000 (ml/g), corresponding to about 95% removal efficiency of the dioxin from solution per batch. For hexachlorohiphenyl, the distribution coefficient was 30,000 (mi/g), and the removal efficiency was 85%.

Use of Inorgano-Organo-Clays in the Removal of Priority Pollutants from Industrial Wastewaters: Adsorption of Benzo(a)Pyrene and Chlorophenols from Aqueous Solutions

“…A more detailed study by Nolan et al (1989) of OCDD binding to hydroxy-A1 montmorillonite revealed that hydroxy-A1 was perhaps the active component in the binding of OCDD to such surfaces. They postulated that a specific interaction, possibly of the charge-transfer-type complex, between the dioxin molecule and the hydroxy-A1 moiety on the surface was responsible for dioxin adsorption.…”

“…The affinity of the activated carbon for B(a)P appears to have been less than that observed for the IOCs, in marked contrast with the results obtained using PCP (Figure 2). Moreover, the inorgano-clay, hydroxy-A1 montmorillonite, had a significant binding affinity for B(a)P, which is not altogether surprising because Nolan et al (1989) showed from adsorption data for polychlorinated dioxins an even stronger affinity between dioxins and hydroxy-Al montmorillonite. Such a high affinity can be explained on the basis of a possible complexation between electronegative C1 atoms ofdioxins and the Lewis acid sites on hydroxy-A1 montmorillonite.…”

Use of Inorgano-Organo-Clays in the Removal of Priority Pollutants from Industrial Wastewaters: Structural Aspects

“…Experiments using packed beds of hydroxy-Al montmorillonite revealed that octachlorodibenzodioxin (OCDD) was strongly bound to the modified clay columns, and that no breakthrough of OCDD in the effluent was observed . A detailed analysis of the binding of dioxins to hydroxy-A1 montmorillonite suggested that hydroxy-A1 itself may be the active component involved in the sorption of dioxins (Nolan et al, 1989); however, hydroxy-A1 montmorillonite was found to exhibit much weaker adsorption for less hydrophobic, but equally toxic pollutants, such as pentachlorophenol (PCP) (Srinivasan and Fogler, 1987). A similar finding was reported by Zielka and Pinnavaia (1988).…”

Selective Adsorption of Polychlorinated Dibenzo‐p‐dioxins and Dibenzofurans by the Zeosils UTD‐1, SSZ‐24, and ITQ‐4

“…However, there are also disadvantages as the fire hazard due to the formation of hot spots, the adsorption of water, difficulties in the regeneration of active carbon and, therefore, in the waste disposal of the highly contaminated adsorbent material. [7] Consequently, a variety of different materials has been tested as sorbents for dioxins: g-Al 2 O 3 , [6] clays as bentonite and laptonite [6] as well as pillared clays, [8] a variety of zeolites [5,6,9,10] and, recently, also carbon nanotubes. [11] Among the zeolites tested were synthetic zeolite Y, [6] natural zeolite clinoptilolite, [6] a volcanic rock called phonolite containing 45 % zeolite [9] and the zeolite Wessalith DAY.…”