Study On The Adsorption And Degradation Of Emerging Contaminant PPCPs In Aqueous By Iron-based Peanut Shell Biochar Composite Functional Materials

Pharmaceuticals and personal care products(PPCPs)are refractory emerging environmental pollutants,which are widely distributed in aqueous and pose a serious threat to drinking water safety and water recycling.The water treatment technology based on the adsorption and persulfate activation of iron-based biochar,is effective on degradation of the refractory organic pollutants.In view of the difficulty in recycling of biochar,this study used microwave-assisted precipitation method to prepare peanut shell magnetic biochar supported nano-Fe2O3(MMBC)to study the uniform dispersibility and recovery of composite materials.Additionally,the adsorption behaviors and mechanisms of typical antibiotic ciprofloxacin(CIP)were also investigated in this study.In view of the low activation efficiency of persulfate(PS)for biochar,this study prepared peanut shell biochar supported nano valent iron(nZVI/BC)and peanut shell biochar coupled with amorphous Cu-doped FeOOH composite(Cu-FeOOH/BC).The effect of nZVI/BC on the activation and degradation of diatrizoate(DTZ)by PS was discussed.The activation mechanism of PS by nZVI/BC was analyzed.The free radical of PS activated by Cu-FeOOH/BC was identified,intermediate products of tetracycline(TC)degradation were discussed and the reaction mechanism of TC degradation via Cu-FeOOH/BC-PS was elucidated.The specific research contents are as follows:The high performance and low cost magnetic biochar composite-peanut shell biochar supported nano Fe2O3(MMBC),was prepared by microwave-assisted conventional chemical precipitation with agricultural waste peanut shell.Microwave radiation enlarged the specific area and pore volume of pristine biochar and promoted the dispersion of iron oxides.Additionally,microwave effect made the Fe2O3 adhere to the biochar surface firmly and enhanced the magnetism of adsorbent,which is benefical to the repeated use.In the optimun pH 6.0,the adsorption capacity of CIP was 8.30 mg/g,which was higher than that(4.50 mg/g)prepared by traditional chemical coprecipitaiton.The CIP adsorption performance was facilitated and inhibited by background electrolytes SO42-and PO43-,respectively.Five cycle experiments have confirmed that compared with the traditional synthesis method,magnetic biochar by microwave assisted synthesis has more stable properties,higher adsorption capacity of CIP in water.Unique reticular peanut shell biochar(BC)supported nano zero-valent iron(nZVI)composite(nZVI/BC),was successfully synthesized.The problems of nZVI agglomeration and easy oxidation were solved and the activation efficiency of persulfate(PS)was improved,which promoted the removal of DTZ.Experiments show that when the ratio of nZVI to BC is 1:2,nZVI were dispersion well,the largest specific surface area and the highest activation efficiency for PS.The removal of DTZ reached 100%using 25 mM PS and 0.45 g/L nZVI/2BC(mass ratio of nZVI and BC at 1:2)nanocomposite material at pH 3.0 and 25'C.The influencing factors including dosages of nZVI/2BC and PS,temperature and pH,were also investigated.The degradation efficiency of DTZ was improved by the increasing of the PS dosage and the temperature of solution.The removal of DTZ performed well under acidic pH at 3.0?7.0,and followed by a pH>11.0.The radical scavenger experiments at pH 3.0?11.0 revealed that the SO4·-dominated in acidic condition and a large number of HO· were generated under alkaline conditions.The mechanism of PS activation with nZVI/2BC was discussed by examining the transport among Fe0,Fe2+ and Fe3+.Peanut shell biochar(BC)supported on Cu-doped FeOOH composite(Cu-FeOOH/BC)was synthesized using a facile and scalable method and the agglomeration problem of nanomaterials was relieved.Additionally the electron transfer between two metals can further improve the efficiency of PS activation.Novel catalytic composites with different Cu/Fe molar ratios were compared systematically by activating persulfate(PS)for the TC degradation.0.5Cu-1FeOOH/BC(Cu/Fe molar ratio=0.5:1)was confirmed as the optimum activation material and the removal of TC reached 98.0%after 120 min by combining with 20 mM PS at pH 7.0 and 25?.The influencing factors including catalyst loading,PS dosage,inorganic anions and pH on the performance system of 0.5Cu-1FeOOH/BC-PS,were investigated respectively.Reaction rate constants(Kobs)on catalyst dosages(0.05 g/L,0.10 g/L,0.20 g/L and 0.30 g/L)were 0.0072 min-1,0.0101 min-1.0.0244 min-1 and 0.0144 min-1,and 0.0090 min-1,0.0146 min-1,0.0244 min-1 and 0.0178 min-1 for the change of PS concentrations(5 mM,10 mM,20 mM and 30 mM).Increasing the concentrations of catalyst and PS appropriately improved TC degradation,but excessive dosages inhibited the reaction process of TC removal.The TC removal rate was inhibited by inorganic anions with the following order of HCO3->Cl->HPO42->SO42->NO3-.The catalyst showed an excellent recyclability and stability,and the removal efficiency of TC still remained over 90%after five consecutive uses.Coupling of 0.5Cu-1FeOOH/BC and PS can be successfully applied as an effective and stable technique for the treatment of refractory organic pollutants in wastewater.TC molecules are bombarded by SO4·-and HO·,and then decomposed into small molecules by means of ring opening or central carbon cracking and eventually mineralized into inorganic substances such as carbon dioxide and water.Iron-based biochar has good adsorption capacity and recyclability,and can be used for adsorption of antibiotics and other drugs,iron-based biochar activated PS to form SO4·-,which can be used as a stable and effective technology for the removal of organic wastewater such as antibiotics and iodine contrast agents.