Adsorption Of As(V) On Porous Hematite Powder In Aqueous Slotions

The porous hematite through thermal decomposition of goethite concentrate has been proved to be a cheap and effective adsorbent for arsenic removal from water.But the As?V?adsorption capacity of porous hematite may be affected by the co-existence of anions and cations and it's hard to separate porous hematite powder from the liquid.That's the reason to study the influence of co-existence of anions and cations on As?V?adsorption capacity of porous hematite and the column adsorption of As?V?by porous hematite powder supported on sand.These results indicated that the column adsorption of As?V?on porous hematite/sand is technically viable and suitable for a future scale-up.In this work,the effect of different anions and cations on As?V?adsorption performance of porous hematite was studied by measure Zeta potential and As?V?adsorption density of porous hematite.At same time,adsorption isotherm and adsorption kinetics were used to fit the adsorption.And the particle size of porous hematite powder has been selected to fill the adsorption column.Breakthrough curves were obtained at different weight of porous hematite,flow rates and initial As?V?concentrations.By analyzing the characterization of porous hematite:it was known that porous hematite could be efficiently prepared by the thermal modification of goethite concentrate at 300?,surface area of porous hematite improved from 8.85m²/g of goethite to 73.27m²/g.By analyzing the experiment data of different anions and cations on the As?V?adsorption performance of porous hematite:The inhibitory effects of PO₄^3-and HCO₃^-on arsenic adsorption may be attributed to the competitive adsorption mechanisms.On the other hand,in the presence of PO₄^3-or HCO₃^-,the surface charge of porous hematite was more negative and porous hematite adsorbed anionic As?V?more hardly.The promoting effects of Ca²⁺and Mg²⁺ions may be resulted from the adsorption mechanisms of co-precipitation.On the other hand,in the presence of Ca²⁺or Mg²⁺,the surface charge of porous hematite was more positive and resulted of the adsorption of anionic As?V?more easily,and K⁺,Na⁺,Cl^-,NO₃^-,SO₄^2-did not show any significant effect on As?V?adsorption.By analyzing the experiment data of column adsorption of As?V?on porous hematite/sand:As?V?adsorption performance of porous hematite through thermal decomposition of different particle size goethite concentrate is different.The particle size of porous hematite did not show any significant effect on As?V?adsorption density because of same surface area.But particle size of porous hematite showed remarkable effect on As?V?adsorption rate because smaller particle size has more adsorption sites on the surface of porous hematite.Effluent turbidity of fixed bed could reach less than 1NTU when porous hematite is larger than 38?m and quartz is about 280?m.As load in columns was 0.744mg/g before water standard of 50?g/L As under the conditions that flow rate was 5mL/min and initial concentration was0.2mg/L.