Cu-Modified Montmorillonite/Chitosan Composites As Diclofenac Sodium Adsorbents

PPCPs(Pharmaceutical and Personal Care Products)is a kind of emerging contaminants,was detected with a high frequency and concentration in medical treatment and other water,including caffeine,ibuprofen,diclofenac sodium,carbamazepine and other daily antibiotics.As an non-steroidal anti-inflammatory drug,diclofenac sodium has good clinical effect,under high dosage and wide application,thus being easily enriched in water,accumulated in food chain and ecological environment pollution.The existing methods of water treatment to remove diclofenac sodium are efficiently limited,so a kind of green environmental protection and efficient system is necessaty to realize the effective removal of diclofenac sodium.Because of the coordination interaction between diclofenac sodium and copper ion,in this work,montmorillonite(MMT)is firstly selected as adsorbent with copper modification based on the laminated structure of montmorillonite and the characteristic of the interlayer ion exchange,in order to achieve the adsorption of diclofenac sodium.Further chitosan(CS)is considered as adsorbent of copper modification through the interaction between the amino and the copper ion of the electrostatic attraction and chemical combination,aiming for the removal of diclofenac sodium.In this paper,the single montmorillonite of modification,the single chitosan of modification and chitosan/montmorillonite composite system modified by the copper respectively,are focused on the behavior and mechanism of diclofenac sodium adsorption,to obtain a green and high efficient performance of the recycled adsorbent,probably as the reference for diclofenac sodium water treatment.Firstly,through the characteristic of interlayer ion exchange for copper,OMT-Cu particles as the diclofenac sodium adsorbent were prepared: the adsorbent has layer structure,according to the adsorption experiments,from p H 4.5 to 9.0,the adsorption capacity of diclofenac sodium was 0.1028 mmol/g at 30 min and the removal rate was above 90 %,well-fitting with Sips isotherm model and the pseudo second-order kinetic model.When the concentration of sulfamethoxazole in the solution was 0.5 mmol/L,the removal efficiency can reach more than 95 %,OMT-Cu therefore has a good adsorption selectivity.Second,by the coordination characteristics between the amino and the copper ion,the Cu-modified crosslinked chitosan adsorbent for DS adsorption was investigated: The adsorbent showed the grid structure,with the contact between adsorbent and adsorbate.From p H 4.5 to 9.0,the adsorption capacity of diclofenac sodium was 0.0472 mmol/g at 20 min and the removal rate was above 90 %,well-fitting with Sips isotherm model and the pseudo second-order kinetic model.After ten recycle times,the efficiency of diclofenac sodium removal can remain 90 %.CS-Cu has good regeneration performance.Finally,in order to get both high adsorption capacity,quick absorption rates and good adsorption selectivity system,on the basis of the OMT-Cu and CS-Cu,the copper modified montmorillonite/chitosan composite particles(OMT-CS-Cu)were obtained: The composite adsorbent showed good layer-grid structure and mechanical properties.From p H 4.5 to 9.0,the adsorption capacity of diclofenac sodium was 0.3345 mmol/g at 20 min and the removal rate was above 95 %,well-fitting with Sips isotherm model and the pseudo second-order kinetic model.At 30 ℃,the maximum adsorption capacity of diclofenac sodium could reach2.5746 mmol/g.After ten recycle times,the efficiency of diclofenac sodium removal can remain 65 %.When the concentration of sulfamethoxazole in the solution was 0.5 mmol/L,the removal efficiency of DS can remian more than 80 %.OMT-CS-Cu thus was a green,renewable and good selective adsorbent.