Study On Methods Of Removing Several Metal Ions From Industrial Wastewater

Recently, the treatment of different industrial wastewater and sewage has become one of the increasingly focused issues. Especially, how to remove metal ions from wastewater are hotspots of this field. Heavy metal ions do a lot of harm to human's health through food chain, even causing death. While non-heavy metal ions, such as calcium and magnesium, can cause high hardness of water. All these problems influence human's development. Among the existed methods of removing metal irons from wastewater, using natural polymers and inorganic mineral materials is one comparative cheap, non-poison and easy operated way. In this thesis, removing heavy metal ions from aqueous solutions by natural polymer –insoluble starch xanthate (ISX) was investigated. On the ground of optimized method, ISX was synthesized with a cleaner and cheaper way than literature. Furthermore, several mineral materials were evaluated and modified to remove Cu(II),Ca(II) and Mg(II) from simulated wastewater. Finally, through combined different ways of removing metal ions, a simple, clean and cheap process was established to remove several metal ions in wastewater. The main results can be summarized as following: 1, Through recycling alkali solution from waste liquor of reaction and substituted solvent drying by freeze drying, the effluent amount of waste liquor was reduced. A cleaner synthesis process of ISX was developed. The percent of copper ions exchanged and adsorbed from simulated wastewater with our ISX is higher than that of literature by 2%. The cost of raw materials is lower than that of present method by 90%, and the raw materials cost of treatment of real industrial wastewater containing copper is 0.52 yuan/ton wastewater. 2, The ISX is used to efficently removing Cu(II) and Fe(II). The percent of metal ions exchanged and adsorbed from wastewater is 99.5% at least with our ISX at pH 2.5~4.1 and stirred for 25 min. The concentration of residual ions Cu(II) is 0.063 mg/L ,while Fe(II) 0.026 mg/L , which all meet National effluent limits. 3, 98.9% copper ions can be recovered when ISX-metal sludge was soaked by 4 mol/L HNO3 for 3 h. The soaked sludge can be directly applied to adsorb metal ions, or regenerated to new ISX through further xanthated reaction. Adsorption performance of the soaked sludge for copper ions is 38% of original. Adsorption performance of the ISX regenerated by our proposed procedure is almost the same as original ISX. All of these benefits offer a feasible process for sludge treatment. 4, Considering adsorption effect and raw materials cost, several inorganic mineral materials e.g. sepiolite, vermiculite and zeolite were evaluated. Finally, zeolite was selected for removing metal ions. Raw Zeolite was modified under the following optimized conditions: soaked by 36% NaCl at 90℃for 1 h, the ratio of soaking solvent and zeolite 1.5. The zeolite modified by Sodium is proved more efficient than that of present method. At the same time, amount of water used in this process is reduced sharply and the cost is lower than that of literature by 28%. 5, The column filling modified zeolite can be used for treatment 840 bed volume wastewater containing copper ions (C0=13.5 mg/L) at the fluent rate 2 mL/min and pH 5.3. The effluent from the column meets National effluent limits. The zeolite column can be revived with a solution (10%HCl:36%NaCl=1:1) and the raw materials cost of treatment is 0.20 yuan/ton wastewater. 6, Three metal ions: Cu(II), Ca(II) and Mg(II) can be efficiently removed from wastewater through a combination of ISX with cation exchange resin. The metal ions concentrations of effluent are 0.01 mg/L for Cu(II), 0.05 mg/L for Ca(II) and 0.01 mg/L for Mg(II), respectively, while whole raw materials cost of treatment is 0.85 yuan/ton wastewater.