Study On The Modification Of The Natural Manganic Ore And Its Adsorbent Activity For Heavy Metal Ions

Wastewater containing heavy metal ions is a kind of industrial water which is great harm to ecological environment, and the heavy metal ions directly threaten human health because of entering into environment by food chain. In order to enhance the adsorptive capability of the natural manganese ore for heavy metal ions from aqueous solution, four kinds of modified manganese ores were prepared through the oxalic acid modification method, the citric acid modification method, the hydrazine hydrate modification method, and the sulfate acid modification method respectively. Adsorptive capacity of heavy metal ions onto the modified manganese ores and the natural manganese ore were comparatively investigated. The reaction conditions of the oxalic acid modification method affecting the adsorptive capacity for heavy metal ions through orthogonal test were investigated. Studies on influential factors of heavy metal ions onto the oxalic acid modified manganese ore and competitive adsorption were discussed in detail and look forward to application prospects of the oxalic acid modified manganese ore on actual electroplating wastewater.The experimental results showed that the pH-adsorption curves and pH50 of the modified manganese ores significantly inclined to lower pH than that of the natural manganese ore. Compared to the natural manganese ore, the maximum adsorbed amounts of Cu2+ onto the modified manganese ores increased 1.5～6.5 times. For the modification methods tested, the order of the effectiveness in increasing Cu2+ adsorption onto manganese ore was the oxalic acid≈the citric acid>the hydrazine hydrate>the sulfate acid. Furthermore, the saturated modified manganese ores can be desorbed and regenerated readily with diluted acid. The experiment showed it expects being a potential novel adsorbent for heavy metal ions.The reaction conditions of the oxalic acid modification method affecting the adsorptive capacity for Cu2+ through orthogonal test were investigated, including vitriol concentration of medium, reaction time, reaction temperature and the dosage of potassium permanganate. The experimental results showed that the order of the four factors that influenced the adsorptive capacity for Cu2+ of the oxalic acid modified manganese ore in order of their importance were the dosage of potassium permanganate>acidity>modified time>temperature. The optimum conditions of reaction were: vitriol concentration of medium 1mol/L, reaction temperature room temperature, reaction time 30 minutes, and the dosage of potassium permanganate 0.5 mmol/g(mineral powder).The oxalic acid modified manganese ore and unmodified natural manganese ore were used as adsorbents for removal of Cu²⁺, Ni²⁺, Zn²⁺, Cd²⁺ and Cu(NH₃)₄²⁺ in water. The adsorption percentage of Cu²⁺, Ni²⁺, Zn²⁺, Cd²⁺ and Cu(NH₃)₄²⁺was investigated as a function of pH values, adsorption time and the adsorbent dosage. In addition, the adsorption isotherms were determined. The experimental results showed that the pH-adsorption curves were of S type for free state heavy metal ion, and M type for Cu(NH₃)₄²⁺. The adsorption percentage of different ions was increased with the growth of adsorption time and the increase of the addition amount of modified manganese ore. The adsorption isotherms of different ions onto manganese ores were fit for Langmuir or Freundlich equation. Interface adsorptive capacity of natural manganese ore was improved by natural manganese ore obviously.The adsorption behaviors of Cu²⁺, Ni²⁺ and Zn²⁺ onto the oxalic acid modified manganese ore with and without competing metal ions were examined in this study in order to provide evidence for further research on adsorption mechanism of heavy metal ions onto the oxalic acid modified manganese ore.The experimental of orthogonal test results showed that pH values is a very important controlled condition in removing heavy metal ions. The optimum conditions of reaction of treating electroplating wastewater were: pH values 7.0, reaction temperature room temperature, reaction time 60 minutes, and the dosage of the manganese ores 2g/L. The nickel content was greatly lower than the national standard after treating.