Studies On Preparation Of Sheep,Cow Bone Char And Adsorption Performance For Hg (Ⅱ)

The main component and pyrolysis characteristics of the sheep, cow bone wasconfirmed by thermal and component analysis.The preparation conditions such asactivator concentration, dipping time, activation temperature, activation time of bonecharcoal were optimized by using the orthogonal and single factor experiment.The effect of adsorption time, pH and adsorbent amount on Hg （II） adsorptionand the maximum adsorption capacity of bone char was examined in the staticadsorption experiment to wastewater containing heavy metals Hg （II） using the sheep,cow bone charcoal; The desorption agent type and mechanism of bone char wasanalyzed. Energy spectrum, BET, scanning electron microscopy, X-ray diffractionmethod had been used to characterize the bone char’s pore structure.Adsorption data for Hg （II） uptake by sheep, cow bone charcoal were analyzedaccording to Langmuir and Freundlich adsorption models and the parameters werecalculated.The results as follows:The optimum preparation conditions for sheep bone char were the concentrationof zinc chloride is0.5g/L, dipping time36h, charring temperature800℃andcharring time is40min. The specific surface area of sheep bone char was83.98m²/g.and the pore dimeter15.39nm, pore volume0.246cm³/g. The bestadsorption conditions of sheep bone char to Hg（II） were as follows: adsorption time2h, pH3, bone char dosage0.5g, the initial Hg（II） concentration400mg/L. Themaximum adsorption volume for Hg（II） is20.6mg/g.The adsorption isotherm of mercury sorption by sheep bone char was fitted toFreundlich isotherms. Adsorption isotherm curve in the sorption isotherm of Brunauerfive type belongs to the type II, conforms to the multi-layer adsorption isotherm.Thepositive values of both H°and S°suggest an endothermic reaction, increasing in randomness at the liquid-solid interface during the adsorption process. G°valuesobtained were negative, indicated that the adsorption of the Hg（II） ion on the surfaceof sheep bone char was a spontaneous adsorption process. The kinetics process can bedescribed by a pseudo second-order rate equation very well.The optimum preparation conditions for cow bone char were the concentration ofzinc chloride is0.5g/L, dipping time36h, charring temperature800℃and charringtime is40min. The specific surface area of sheep bone char was239.63m²/g.and thepore dimeter7.109nm, pore volume0.423cm³/g. The best adsorption conditions ofsheep bone char to Hg（II） were as follows: adsorption time2h, pH1, bone chardosage0.5g, the initial Hg（II） concentration600mg/L. The maximum adsorptionvolume for Hg（II） is48.8mg/g.The adsorption isotherm of mercury sorption by cow bone char was fitted toFreundlich isotherms. Adsorption isotherm curve in the sorption isotherm of Brunauerfive type belongs to the type II too, conforms to the multi-layer adsorptionisotherm.The positive values of both H°and S°suggest an endothermic reaction,increasing in randomness at the solid-liquid interface during the adsorption process.△G°values obtained were negative, indicated that the adsorption of the Hg（II） ion onthe surface of sheep bone char was a spontaneous adsorption process. The kinetics ofmercury sorption by cow bone char was ideally conformed to pseudo-secondequation.Among the different desorption agent（H₂SO₄, HNO₃, HCI）, the desorption rateof HNO₃to Hg （II） is better. When concentration is0.1mol/L, the desorptionefficiency reached80%.