The Preparation Of Magnesium Oxide-biochar And Study On Its Adsorption Performance For Heavy Metals Arsenic,Lead And Copper

Nowadays,heavy metals have be regarded as the main pollutants,which are one of the pollution problems that need to be solved urgently,and have attracted extensive attention from researchers.In recent years,researchers have developed variety methods to remove heavy metal.At present,the adsorption method is considered to be one of the most effective methods for heavy metal removal.In this paper,a millimeter-sized porous granular MgO-biochar(g-MgO-Bc)adsorbent was prepared by the gelationcalcination method for the removal of heavy metals As(Ⅲ),Pb(II)and Cu(II)in water.The effects of various conditions and different interfering substances on the removal of As(Ⅲ),Pb(II)and Cu(II)have been studied.Moreover,the removal mechanism of As(Ⅲ),Pb(II)and Cu(II)has been deeply studied.The main contents are as follows:(1)Three kinds of g-MgO-Bc adsorbents with different magnesium content are prepared for the removal of As(Ⅲ).High-density MgO nanoparticles are evenly dispersed throughout the biochar matrix and can be fully exposed to As(Ⅲ)through the pores in g-MgO-Bc.These features endow the adsorbent with a high adsorption capacity of 249.1 mg/g for As(Ⅲ).The g-MgO-Bc can efficiently remove As(Ⅲ)over a wide p H of 3-10.The coexisting interfering substances,such as carbonate,nitrate,sulfate,silicate and humic acid exert a negligible influence on As(Ⅲ)removal.And it exhibited excellent removal effect on trace As(Ⅲ),where only 0.3 g/L g-MgO-Bc can remove 300 μg/L of As(Ⅲ)to less than10 μg/L.The spent g-MgO-Bc could be well regenerated by simple calcination without any decrease in adsorption efficiency.In addition,in the fixed bed column adsorption experiment,the effective treatment volume of simulated As(Ⅲ)wastewater reached 1500 BV(30 L)(3 g of adsorbent,effective bed volume of 20 m L,solution flow rate of 2.0 m L/min,initial As(Ⅲ)concentration of 50 μg/L).Therefore,this novel g-MgO-Bc adsorbent extended the potential applicability of biochar adsorbent for As(Ⅲ)removal to a great extent.(2)The above adsorbent was used to remov e heavy metals Pb(II)and Cu(II).The adsorbent not only showed a fast adsorption rate for the removal of Pb(II)and Cu(II),but also has a large adsorption capacity.For the adsorption kinetics of 100 mg/L of Pb(II),the adsorption equilibrium can be reac hed within 10 min.The maximum adsorption capacities of g-MgO-Bc-1.5,g-MgO-Bc-2.0 and g-MgO-Bc-2.5 for Pb(II)are 662.4,736.4 and 907.6 mg/g,respectively.For the adsorption kinetics of 50 mg/L Cu(II),the adsorption equilibrium can also be reached with in 60 minutes.The maximum adsorption capacities of g-MgO-Bc-1.5,g-MgO-Bc-2.0 and g-MgO-Bc-2.5for Cu(II)are 540.9,587.0 and 714.8 mg/g,respectively.At the same time,the adsorption of Pb(II)and Cu(II)can be effectively removed in the p H range of 2-7,and it also shows excellent adsorption effect under the interference of different cations.The adsorbent can be recycled by simple desorption-drying and the adsorption efficiency is not reduced.In addition,the adsorbent can also be used in fixed bed adsorption experiments to effectively remove Pb(II)and Cu(II),the effective treatment volume of simulated Pb(II)wastewater reached 7880 BV(78.80 L)(1.2 g of adsorbent,effective bed volume of 10 m L,solution flow rate of 2.0 m L/min,initial Pb(II)concentration of 20 mg/L),the effective treatment volume of simulated Cu(II)wastewater reached 1610 BV(16.10 L)(1.25 g of adsorbent,effective bed volume of10 m L,solution flow rate of 2.0 m L/min,initial Cu(II)concentration of 5 mg/L).In conclusion,the adsorbent shows great potential for the removal of heavy metals Pb(II)and Cu(II)in actual water.