Preparation Of Iron-loaded Activated Carbon And Study On Adsorption Properties Of PFOA

Perfluorooctanoic acid?PFOA?has the reproductive toxicity,mutagenic toxicity,developmental toxicity and so on,Gradually attracted the attention of researchers and scholars.Activated carbon as adsorbent has the advantages of simple operation,high efficiency and feasibility,and is often used in water treatment and emergency treatment of sudden water pollution.However,the conventional activated carbon adsorbent has poor adsorption capacity?relatively small adsorption capacity,slower adsorption rate,narrower effective pH range,etc.?,Therefore,based on the research and development and the practical application of the new environmental materials,we chooose different divalent and trivalent ferric salts to impregnate and modify the granular activated carbon to prepare the composite materials with iron salts.By experimental comparison,the effects of different ferric salts and their concentration and maturation temperature on the adsorption performance of PFOA were studied,The best composites were selected for the follow-up study.Using scanning electron microscopy?SEM?,specific surface area and pore size?BET?,X-ray diffraction?XRD?,Fourier transform infrared spectroscopy?FTIR?analysis on material characterization,examining the physical and chemical characteristics of activated carbon before and after the modification.The effects of initial concentration of solution,pH value,anion,humic acid and dosage of materials on the adsorption of PFOA on modified activated carbon were investigated.The kinetics and isotherm model were used to fit the adsorption process of adsorbent PFOA.The results showed that:FeCl₂·4H₂O,FeCl₃·6H₂O,Fe SO₄·7H₂O,Fe?NO₃?3·9H₂O solution were loaded on the granular activated carbon with the same concentration.supported ferric salt on the surface of activated carbon by the infiltration method,A new type of composite material was prepared and then the removal of PFOA was carried out.The optimum conditions for the preparation of the composite material was as follows: the concentration of ferrous chloride solution was0.2mol/L,the curing temperature was 120?,and the adsorption efficiency of PFOA was the best,removal rate reaching 94.9%.Compared with GAC,the Fe-GAC specific surface area is decreased,the total pore volume and pore size are also reduced.The XRD pattern also showed the weak characteristic curve of iron oxide was at about 23.25°,33.07°and 55.32°,FTIR chart shows that 566.98-570.84cm-1,484.05cm-1appear obvious Fe-O absorption peak,Indicating that iron wassuccessfully loaded on the activated carbon surface,and the value of its zero charge point between 2-3,With the increase of pH value,the surface charge from positive to negative charge.When the dosage of adsorbent keep certain,the initial concentration increases and the corresponding removal rate decreases,The removal rate of Fe-GAC to PFOA decreased from95.99% to 84.57%;With the increasing of pH value,the adsorption capacity decreased;As the "salting-out effect",The increase of salt ion strength makes the PFOA easier to precipitate,which is favorable for adsorption;The removal rate of PFOA was changed with the dosage of adsorbent,and the removal rate was significantly increased when the dosage of adsorbent was increased from 0 to 0.15 g.HA and PFOA are easy to compete for adsorption,which occupy the adsorption sites of the adsorbent,and reduce the adsorption efficiency.The Langmuir adsorption isotherm equation can better fit the adsorption process of PFOA on the adsorption isotherm model.The correlation coefficient R2 is above 0.98.In the model of adsorption kinetics,the adsorption process of the two materials can be better fitted by pseudo second-order reaction kinetics model,and the calculated qec and qe are basically consistent.The mechanism of the removal of PFOA by Fe-GAC and GAC was explored.The adsorption process is chemically adsorbed and belongs to monolayer adsorption,The adsorption of PFOA by the adsorbent presents a transition from the rapid reaction stage to the slow reaction phase and finally to an adsorption equilibrium stage,and the electrostatic action is present in the adsorption process.