| The arsenic pollution in water has been a serious accident in recent years, it is threatening the human health. In this study, manganese ore and its modified magnetic composite ferromanganese were employed to deal with the arsenic in water. A series of physical and chemical experiments were conducted to learn the ore’s adsorption capacity and mechanism on arsenic, and then a modified way on ore was explored for better adsorption. The divalent manganese ore was leached by an original modified high temperature roasting method. And the leachate was used for synthesis of magnetic Fe and Mn complex (MFM for short).The studies had shown that manganese ore could deal with low arsenic concentration (C<0.1mg/L) water, when manganese dosage remained at 1.25g/L, the operating conditions were as follow:under 25 ℃, the initial arsenic concentration was 0.1mg/L,pH value of 3. Arsenic concentration in the solution was less than 0.01mg/L after 24h reaction. Fe3+ and Ca2+ contributed to adsorption efficiency, and coexist ion HCO3- in water could reduce the efficiency of adsorption.Adsorption process fitted the Freundlich isotherm model and the pseudo-second order kinetic model; Mn-OH, α-FeOOH and α-Fe2O3 are the major groups of adsorption. Throughout the adsorption process, arsenic anions form inner-sphere surface complexes, and the type of adsorption is specific adsorptionThe MFM was prepared for treating higher initial concentration of arsenic(C> O.Olmg/L) and it was synthesized mainly by the leachate of manganese ore. The first step is leaching. The results of single factor experiment showed that optimum operating conditions for leaching the divalent manganese ion were:roasting temperature was kept at 700℃, quality ratio of sulfuric acid-to-ore ratio of 1.05:1, iron-to-ore ratio of 0.14:1, liquid-to-solid ratio of 6:1, leaching temperature of 50℃, and leaching efficiency can reach 92.63% after 2 hours leaching time. And the mass ratio of iron-to-manganese is 1:1. With ferroferric oxide as the core, ferric chloride solution was added into the leachate to adjust the mass ratio of iron-to-manganese remain 3:1, then after precipitation reaction of sodium hydroxide and oxidation reaction of sodium hypochlorite, the MFM was carried out for adsorption.Through physical and chemical characterization, it could be found that the MFM was found to be an amorphous complex and contain Has a rich effective groups like Mn-OH, α-FeOOH, Fe-O on the surface. And it has the ability to deal with high arsenic concentration water. The specific operating conditions were as follow:At room temperature, adsorbent dosage of 0.1g/L, the pH ranged from 3 to 7, the initial arsenic concentration of 0.4mg/L can be reduced to lower than 0.01mg/L.Experimental results showed that:there were some changes on the reaction conditions between the low-grade manganese ore and the MFM. The reaction conditions of MFM broadened the scope of the experimental optimum pH value from 3.3 to a wide range of 3 to 7, the dosage was about 1/10 times of manganese ore, the equilibrium reaction time was about 1/9 times of it, and the maximum concentration was expanded from 0.1mg/L to 0.4mg/L, and solid-liquid separation could be easily achieved by magnet. The development prospect of the MFM is promising. |
PDF Full Text Request