Study On The Adsorption Behavior Of Re(?) Onto Cu-coated Bio-chars

Rhenium(Re)is a strategic rare metal element which has been widely used in the fields of aerospace industry and petrochemical industry,the demands of the global rhenium continue to increase recently.Rhenium often flow into aqueous solution in the form of Re(?)in the smelting process.In view of the scarcity of rhenium,the rhenium separation and recovery in aqueous solution are of great significance.In recent years,bio-char has been widely concerned by researchers due to its low cost,environmental protection and excellent performance etc.In this study,Acidosasa edulis shoot shells(AESS)were selected as feedstock to produce Cu-coated bio-chars by the impregnation method at different pyrolysis temperature to recovery Re(?)from aqueous solution.The physicochemical properties of Cu-coated bio-chars were characterized by BET,ATR-FTIR,SEM-EDX,XPS and XRD.Besides,the adsorption behaviors and mechanisms of Re(?)onto Cu-coated bio-chars were studied.The main conclusions were presented as follows:(1)The Cu-coated bio-chars can be used as a prospective adsorbent for the recovering Re(?)from aqueous solution.The capacity of bio-char adsorption Re(?)under weak acidic condition(pH=3-6)was significantly improved by coating Cu species and the maximum adsorption capacity of Cu-coated bio-chars sorption Re(?)was 17.79 mg·g-1.(2)The adsorption of Re(?)by Cu-coated bio-chars is a complicated process,which mainly through electronic attraction and surface complexation.The adsorption capacity of engineered biochars was increased by 3?12 times at pH 3-6 compared with pristine biochar.(3)The optimal pH value is 1,the best adsorbent dosage is determined at 3 g·L-1 and the adsorption equilibrium is obtained at 8 h of Re(?)adsorption onto Cu-coated bio-chars.The adsorption capacity is increased with the increasing initial Re(?)concentration in the experimental range.The adsorption of Re(?)onto Cu-coated bio-chars is an endothermic process and the bio-chars showed a better adsorption properties to Re(?)with the increasing of temperature.(4)The kinetics data are best described by the pseudo-second order model.The adsorption process is controlled by liquid film diffusion and intraparticle diffusion and the film diffusion is the rate controlling step of the whole adsorption process.Redlich-Peterson model(three-parameter model)could describe the equilibrium data better.The adsorption process is spontaneous,endothermic and the increased randomness at the solid/solution interface after Re(?)adsorption.(5)0.1 mol·L-1 KOH solution is a suitable Re(?)desorption agent.After four adsorption-desorption cycles,the desorption rate is still up to 92%at room temperature.