| Abstract [eng] |
Metal complex dyes are a problematic group of substances, present in the negatively charged anion form in mixed industrial wastewater that should be removed. Therefore, a complete removal of these hazardous dyes from wastewaters is necessary to prevent them from release into the environment. Adsorption on activated carbon of dyes has been investigated widely. However some disadvantages using activated carbon in practice were observed, e.g. high regeneration costs and production of fines due to the brittle nature. Since their adsorption capacities, mechanical strength, and other properties need further improvement for wider application, the polymeric sorbents are still under development as a potential alternative to activated carbons. The main aim of the present work was to investigate absorption regularity metal complex Lanasyl Navy M-DNL and Acid Blue 249 (copper (II) phthalocyanine) dyes on synthetic ion exchangers under static conditions and evaluate facility of ion exchangers to removal dyes from wastewaters by dynamic conditions. Screening with chromium-complex dye (acid brown NKM, Lanasyn Navy M-DNL) solutions wide range sorbents, according to the physical chemical characteristics of sorbents and established dye removal parameters (sorption capacity, distribution coefficient and sorbent regeneration) has shown that the polyacrylic, gel type, weakly basic anion exchanger Purolite A 847 (A 845); polystyrene, macroporous, strongly basic anion exchanger Purolite A 500 PS and nonfunctionalized Macronet MN 200 are the most promising sorbents for the metal complex dye removal. Removing chromium-complex and copper-complex dyes using selected sorbents has been investigated in batch and column experiments with respect to solution concentration, pH and temperature. The sorption capacity for sorbents strongly depends on solution pH with higher values at acidic pH. The kinetics studies, combined with optical microscopy and FT-IR, were conducted to reveal the relation between the physical-chemical characteristics of the sorbents and their performance in the removal of metal-complex. With an increase in the solution temperatures from 293 K to 333 K the dye Navy sorption capacity on both anion exchanger A 847, A 500PS and on MN 200 increase, whereas the dye CuPc decrease. The experimental data showed good correlation with Langmuir and Freundlich theoretical isotherm models for all systems Navy-sorbent. The data of the systems CuPc-sorbent satisfies only Freundlich mathematical model. The sorption mechanism onto selected sorbents investigated consist physical and diffusion of anion exchangers and MN 200 using two theoretical (pseudo-second order and Weber-Moris intraparticle diffusion) models. Pseudo-second order kinetic model is suitable to determination of equilibrium sorption capacity and rate constant according to the dye Navy and dye CuPc. The Weber-Moris intraparticle diffusion model was used for calculation the intraparticle diffusion coefficient (ki) and for indirect evaluation of the influence of boundary layer, which is formed about the sorbent bead. Determinate boundary layer thickness for sorption dye Navy on both anion exchangers was about few rows biggest neither for dye CuPc sorption, and-1.5 time for sorption Navy dye neither for CuPc dye on MN 200. Investigate the thermodynamic parameters (G0, H0 and S0) for dyes sorption on sorbents. On the static condition high metal complex dyes removal efficiency (Cr 36 – 100 %, Cu 86-94 %) was obtained for dye Navy interaction with A 847 (A 845) at initial solution pH 2 and with Macronet MN 200 (only at low initial dye concentration (<3.08 mg/l) in solution) and can satisfy the environmental requirement for chromium concentration less than 0.1 mg/l and COD less than 150mg/l. Several models were applied to the experimental data obtained from dynamic studies performed on fixed bed columns to predict the breakthrough curves and to determine the column kinetic parameters. The simulation of the whole breakthrough curve is effective with Bohart-Adams and Juang models for sorption dye Navy and dye CuPc onto Purolite A 847 and with the Bohard-Adams for sorption dye Navy onto nonionic MN 200. A linear relationship between ln(c/c0) and the time at a given bed height and flow rate was obtained in the initial region of effluent concentration (c0.5 c0), suggesting that this segment of the breakthrough curve fit Wolborska model, and allows estimating the kinetic mass transfer coefficient in the fixed bed. The mass transfer in the system anion exchanger and one-component dye solution depended on the concentration of the sulphonate groups in the chemical structure of dye molecule and was lower for the dye with four-sulpho groups (C.I. Acid Blue 249) than that for the dye containing two-sulphonate groups (Lanasyn Navy M-DNL). Whereas the mass transfer in the dye mixture is significantly hindered by the possible competition effect between uniform negative charges of both dye anions to the positive electric charge on amine functional groups of anion exchanger. The column capacity for Purolite A 847 and MN 200 was found to be higher than the batch capacity. It is possible to regenerate the anion exchanger quantitatively (70%) recovering the dye with mixture of 4% NaOH and ethanol (1:1). The regeneration MN 200 with methanol is perfect (100 %). |
