Removal of Chromium, Copper, Zinc and Nickel from Aqueous Solutions Using Wine Processing Waste Sludges

• Main Authors: Cheng-Chung Liu, 劉鎮宗
• Other Authors: 王明光
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/41539917753346105684

博士 === 臺灣大學 === 農業化學研究所 === 96 === Wine processing waste sludge (WPWS) has been shown to be an effective sorbent for sorption of some heavy metals, but the properties of WPWS and sorption mechanism of heavy metal by WPWS were remained obscured. This study aimed to (i) examine the characteristics of WPWS; (ii) explore the sorption mechanism of WPWS for heavy metals; (iii) determine the effects of temperature, initial concentration of metals and different particle sizes on the adsorption reaction; and (iv) conduct the competitive adsorption by batch and fixed-bed columns methods using Cr, Cu, Zn and Ni as sorbates. The sludges contain high contents of organic matter (38%) and cation-exchange capacity (CEC, 255 cmolc kg-1). From IR analysis revealed that prominent functional groups is carboxyl which interact with metals. The alkyl-C and carboxyl-C were major organic functional groups in WPWS which was quantified by 13C NMR analysis. The composition of inorganic element in WPWS contain Fe, Al, Ca, Mg, K, Na, Mn, Si, N, P and S, which may be complexed by organic matter or exist in amorphous oxides form. Methods of dissolution of inorganic compositions, WPWS rinsing, ion exchange and physical separation were employed to study the properties and aggregates of WPWS and sorption mechanism. Ion exchange is the most important way for WPWS to adsorb toxic metals. The aggregate of WPWS consist of well mixture of organic and inorganic components. Method of physical separation of WPWS can improve the determinations of 13C NMR and Differential scanning calorimetry. The WPWS sorption isotherms of Cr(III) are well described by both Langmuir and Freundlich isotherm, whereas Cu and Ni are well described by only Langmuir isotherms and Zn were Freundlich isotherms. A pseudo-second-order sorption kinetic model describes successfully the kinetics of sorption of Cu, Zn, Ni and Cr(VI) onto WPWS at different operation parameters (i.e., pH, initial Ni concentration, and particle size), but pseudo-first-order shows good compliance with Cr(III) sorption. The sorption of Cr, Cu, Zn and Ni increase with increasing temperature, but it decreases with increasing in metal concentration and particle size. The dissolution of organic matter also increases with increasing temperature. The activated energies of Cu and Zn sorbed by WPWS are 6.961 and 7.820 kJ mole-1, respectively. The column studies showed that the times approach exhausted point for Cu and Zn were 4.0 and 8.2 times greater than that of Cr, respectively. The charge density of metal can affect the sorption time and sorption amount. The retardation factor for Cr, Cu and Zn column are shown the following order: Cr (18.3) > Cu (13.0 )> Zn (7.2), and the order of dispersive coefficient is: Cr (2.36×10-6) > Zn (6.83×10-7) > Cu (7.25.89×10-7) m2 s-1, which is calculated from a one dimensional convection–dispersion model recommended by Barry and Sposito. The dynamic transports of Cu and Zn can be described well by this model, bur for Cr. Thomas equation is not adopted for Cr to determine the maximum sorption capacity The sorption of metals by WPWS show the trend in competitive system: Cr > Cu >Zn. The sorption of Cr is less than that of Cu at low temperature, but the increase in sorption of Cr is more than that of Cu and Zn. The ratios of sorption amount were 6.3:1 (Cr:Cu), 17.1:1 (Cr:Zn), 5.6:1 (Cu:Zn) and 107:18:1 (Cr:Cu:Zn) for Cr/Cu, Cr/Zn, Cu/Zn and Cr/Cu/Zn mixtures with same initial concentration at exhausted point, respectively. Zn can not be sorbed effectively by column method. The adsorbed Zn can be replaced by both of Cr and Cu, but Cr can not replace the adsorbed Cu. The least competitive sorption for Zn(II) can be attributed to its largest hydrated radius and full-filled electric orbital. All kinetic experiments of Cr(VI) sorption were conducted at an initial pH of 2.0, and the final pH of the suspensions were approximately 4.2. Thus, both protonation and the oxidation-reduction reaction weakened, and this led to low Cr removal. Some of the Cr(VI) ions are reduced to Cr(III) ions and then adsorbed on WPWS, as indicated by monitoring using the X-ray absorption near-edge spectroscopic (XANES) technique. The other Cr(III) remained in the liquid phase. The Cr(VI) can also be reduced by little ferrous ions dissolved from WPWS.