Removal Properties And Mechanism Of Diclofenac Using Polypyrrle/Volcanic Ash From Aqueous Solution

In recent years,pharmecuetical and personal care products?PPCPs?were detected frequently in many water bodies over the world.They can pose threat to human,plants and animals.Adsorption has became the most potential technique for removal of PPCPs from water due to high adorption capacity,reproducible adsorbent and so on.However,the current adsorbents have some problems and there is an urgent need to develop a cost-effective adsorbent.In this study,polypyrrole was used to modify inexpensive natural volcanic ash,and a new type of conductive polymer loaded adsorbent was developed.In this study,a typical PPCPs,diclofenac?DCF?was chosen as the target substance.Firstly,a natural volcanic ash with best adsorbability was selected,and then a polyporrole loaded natural volcanic ash composite adsorbent?PPy/VA?was synthezed using chemical method.The optimum mixture proportion of PPy/VA was determined using the simplex-centroid mixture design provided by Minitab statistical software.The DCF adsorption properties?initial DCF concentration,initial pH,temperature,contact time,isotherms,kinetics,selecticity,et al?on natural volcanic ash and PPy/VAwere explored respectively.The adsorption mechanism was also discussed combined with the results of characteristics?BET,XRD,SEM,FTIR et al?.The results showed that the optimum proportions were 0.26 volcanic ash,0.10pyrrole,and 0.64 FeCl3.Furthermore,lower drying temperature made the higher DCF removal efficiency.The natural volcanic ash and PPy/VA were both mesoporous material.The natural volcanic ash has a smooth surface and the main crystal composition of it was dolomite?CaMg?CO₃?₂?while PPy/VA has loose surface and its main crystal composition was quartz?SiO₂?.The optimal pH of DCF adsorption onto natural volcanic ash was 2 while the DCF removal efficiency remained stable in the pH range from 3 to 10 with removal efficiency around 95%as for the adsorption onto PPy/VA.Both adsorption processes were exothermic processes and complex multi-layer adsorptions.Both of adsorption processes fitted pseudo-second order model well,the adsorption equilibrium time for DCF adsorption on natural volcanic ash was 300min,and it reduced 60 min for PPy/VA.The natural volcanic ash has high selectivity for DCF.It had low desorption rate and good regeneration when PPy/VA was desorbed by HCl solution compared with NaOH solution.The possible adsorption mechanisms of DCF onto natural volcanic ash were electrostatic interaction and the interaction between H and O.And it were mainly electrostatic interaction,stearic acid salt formation,dipole-dipole intermolecular force,hydrogen bonding and ?-? interaction for DCF adsorption onto PPy/VA.