Methods For The Removal Of Organic Dyes And Heavy Metal Salts From Wastewater

For treating pollutants from wastewater, the method of adsorption and PMS activation were developed to organic dyes and heavy metal salts in this paper. For organic dyes,amino-modified magnetic nanoparticles Fe₃O₄@SiO₂-NH₂ was prepared for the adsorption of organic dyes, and new metallic cobalt loaded magnetic nanoparticles（Fe₃O₄@C/Co） was prepared to activate PMS for oxidation of organic dyes. The two nanoparticles were characterized by FT-IR, XRD, TEM, TGA, XPS and VSM. The effects of several parameters,including the influence on different factors of decolorization, decolorization mechanism,adsorption thermodynamic model, adsorption kinetics, adsorbent（or catalyst） regeneration were investigated. For heavy metal salts, a new Schiff base was synthesized and it was grafted on silica gel（named SG-H₂L）. FT-IR, TGA, elemental analysis and nitrogen adsorption/desorption curve were employed to characterize the properties of the adsorbent.And this adsorbent was used to the co-adsorption of Cu²⁺ and SO₄^2-, including the effect of pH on the adsorption efficiency, selective adsorption of cationic or anionic, adsorption thermodynamics, adsorption kinetics and the adsorbent regeneration experiments. Main conclusions are listed as following:（1） The adsorption kinetics for AO II and X-3B on Fe₃O₄@SiO₂-NH₂ followed the pseudo-second-order kinetic model, and the adsorption equilibrium data fitted well with Langmuir isotherm model. The maximum adsorption capacities for AO II and X-3B at pH 2under room temperature were 132.2 and 233.1 mg g-1, respectively. Desorption of dyes and regeneration of the adsorbent were carried out using aqueous solution at pH 10. The adsorbent Fe₃O₄@SiO₂-NH₂ could be easily recovered by external magnet and it exhibited good recyclability.（2） Fe₃O₄@C/Co nanocomposites exhibited high activity in PMS activation for AO II decolorization. Complete decolorization of AO II solution could be achieved in 20 min within near neutral pH range（pH 6.4–8.5）, while a complete decolorization occurred in 40 min for the as-prepared solution without pH adjustment（pH 4.05）. The increasings of several parameters including pH, catalyst load, PMS concentration and reaction temperature on the catalytic activity also promote the decolorization efficiency. Sulfate free radicals activated from PMS were proposed to be the dominant active species in the “Fe₃O₄@C/Co + PMS”system for AO II decolorization. The catalytic and decolorization mechanism was suggested.The catalyst Fe₃O₄@C/Co could be recycled easily by a magnet with good reusability.（3） The results indicate that SG-H₂ L only adsorb Cu²⁺and SO₄^2-from metal salt waste water. When the pH decreased, the adsorption of Cu²⁺ reduced, and the amount ofadsorption foe SO₄^2- increased. The adsorption kinetics for Cu²⁺ and SO₄^2- on SG-H₂ L followed the pseudo-second-order kinetic model, and the adsorption equilibrium data fitted well with Langmuir isotherm model. The maximum adsorption capacity for Cu²⁺and SO₄^2-was 26.61 mg/g and 23.21 mg/g, respectively. Desorption and regeneration of the adsorbent were carried out by adjusting pH of the solution to achieve the adsorbent recycling.