Sorption Characteristics Of Ibuprofen To Iron Oxide Modified Biochars

In order to remove pharmaceutical and personal care products?PPCPs?from wastewater and reclaimed water and to reduce their environmental risks on groundwater and soils,in this study,biochars?i.e.,wheat straw?WC?,walnut shell?HC?and pig manure?PC??were produced at three heating treatment temperatures?HTTs??i.e.,300,500 and 700?,respectively?.Iron oxides modified biochars were prepared by different concentrations of Fe salt at HTT of 700?.Ibuprofen?IBP?was selected as a target pollutant to investigate the sorption characteristics to biochar and modified biochar by batch experiments and microscopic characterization.The main conclusions are as follows:?1?WC and HC have a higher carbon content than PC,but PC has the highest N,O content and strongest polarity.Consequently,pig manure biochar at HTT of 700??P700?has the greatest sorption capacity of IBP due to the largest specific surface area?SSA,493.9 m²/g?.Walnut shell biochar at HTT of 700??H700?has the weakest sorption capacity of IBP because its low O content can provide little sorption sites.?2?For biochars derived at HTT of 700?,when solution pH is below 7,?-?electron donor-acceptor interactions and H-bonding interactions are the dominating sorption mechanisms.When solution pH is not below7,?-?electron donor-acceptor interactions dominates.Electrostatic force between negatively charged wheat straw biochar at HTTs of 700??W700?andanion IBP?IBP^-?also plays a role when solution pH is below 6.?3?Modification by iron oxides improved the pH_pzc of modified biochars.Modified walnut shell biochar has higher carbon content than modified wheat straw biochar and modified pig manure biochar of which the main component is iron oxide.Modification of walnut shell biochar with0.01 M Fe salt(FH_0.01)increases thespecificsurfacearea by a factor of one,compared with of H700.When the concentration of IBP<10 mg/L,removal efficiency by FH _0.01 reached 95%,main sorption mechanisms include electron donor-acceptor interactions,H-bonding interactions and electrostatic force between protonized iron oxides and IBP.With increasing concentration of Fe salt in modification,the SSA of modified biochars decreases and average pore size diminishes because micropores and mesopores start being blocked.The modified biochars are comprised of magnetite and amorphous biochar can be easily recollected by a magnet in treatment of wastewater.?4?When solution pH is 3⁵,phosphate inhabits the sorption of IBP to W700 by competing electrostatic sites with IBP^-.When solution pH is 5⁹,the sorption inhibition to P700 goes stronger with increasing concentration of phosphate.While phosphate can promote the sorption of IBP to FH_0.01when solution pH is 4⁹.