| With the rapid development of industrial activities,the green and environmentally friendly methods for the treatment of metal pollution and the recycling of resources have received extensive interesting.Thermosensitive ion-imprinted material which has the advantages of thermosensitivity and ion-imprinting technology is potential in processing heavy-metal pollution and exploitation of rare metal resources.In this work,a novel gradient heating procedure was created to fabricate the metal ions-imprinted thermosensitive polysaccharide material from bacterial cellulose(BC)and chitosan(CS)as raw materials,which are rich in Hainan,with N-isopropyl acrylamide(NIPAM)as the monomer and Cu2+/UO22+ions as the template.The structure of the metal ions-imprinted thermosensitive material was characterized by Differential scanning calorimetry(DSC),Fourier transform infrared spectroscopy(FTIR),Raman spectrometer(Raman),Thermogravimetric analyzer(TGA),Scanning electron microscopy(SEM).Finally,the adsorption,desorption and selective adsorption capacity of the template ions were tested.1.The reaction conditions(temperature,time,material ratio and Cu2+ addition amount)were optimized by gradient heating method.The optimum conditions for preparing the Cu2+ imprinted thermosensitive material(ITB)with a gradient heating process was as follows:the ratio of BC to the amount of NIPAM(mol:mol,1:3),0.02 mg/mL of Cu2+concentration.The ITB was obtained through polymerization with the heating gradient of 40 ? for 1 h,50 ? for 1 h,60 ? for 1 h,and 700C for 3 h.The phase change temperature(PCT)of ITB was 38.57 C in the heating procedure,while 30.81 ? in the cooling procedure.Adsorption experiments for TIB,the adsorption amount of Cu2+reached 95.20 mg/g at 45?(>PCT),and the desorption rate was 98.81%by simply washing with water at 20 C(<PCT).After repeating the adsorption-desorption procedure for 5 times,the adsorption amount and desoiption rate remained at 91 mg/g and 97%,respectively.The maximum adsorption capacity of Cu2+ was 140.85 mg/g.The kinetics of adsorption could be well appeared according to the pseudo-second-order equation.Adsorption isotherms was suitable for expression by Langmuir equation..In the mixtures containing metal ions(Mn2+,Ca2+,Mg2+,Fe3+,Pb2+,Cd2+,Zn2+,Cu2+),the adsorption capacity for Cu2+was 81.91 mg/g,while that for other ions was 0.54-9.00 mg/g.The desorption rate of ITB for Cu2+was 98.21%,that for the other ions was 0.33-2.63%.The results indicated ITB had excellent selectivity and desorption to the template Cu2+.2.The reaction conditions(temperature,time,material ratio and Cu2+addition amount)were optimized by gradient heating method.the optimum conditions for preparing the Cu2+imprinted thermosensitive material(CCIm)with a gradient heating process was as follows:the ratio of CS to the amount of NIPAM(mol:mol,1:3),0.01 mg/mL of Cu2+concentration.The CCIm was obtained through polymerization with the heating gradient of 40 C for 1 h,50? for 1 h,60 C for 1 h,and 70? for 3 h.The PCT of CCIm was 35.31? and 26.27 ? in the heating and cooling procedure,respectively.Adsorption experiments for CCIn,the adsorption amount of Cu2+reached 88.94 mg/g at 45 C(>PCT),and the desorption rate was 98.90%by temperature change at 20 C(<PCT).After repeating the adsorption-desorption procedure for 5 times,the adsorption amount and desorption rate maintained at 85.43 mg/g and 97.09%,respectively.The maximum theoretical adsorption capacity of Cu2+was 140.85 mg/g.The kinetics of adsorption and adsorption isotherms could be well showed according to the pseudo-second-order equation and Langmuir equation,respectively.In the mixtures containing metal ions(Mn2+,Ca2+,Mg2+,Fe3+,Pb2+,Cd2+,Zn2+,Cu2+),the adsorption capacity for Cu2+ was 80.23 mg/g,while that for other ions was 0.63-4.26 mg/g.The desorption rate of CCIm for Cu2+was 97%,that for the other ions was 0.62-1.33%.The results showed CCIm had excellent selectivity and desorption to the template Cu2+.3.The gradient heating procedure(40 ? 1 h,50 ? 1 h,60 ? 1h,70 ? 3 h)was adopted to successfully fabricate the UO22+ imprinted thermosensitive material(UTB)from bacterial cellulose with UO22+as the template and NIPAM as the monomer.The gradient heating process was as follows:the ratio of BC to the amount of NIPAM(mol:mol,1:3),0.02 mg/mL of UO22+concentration.The PCT of UTB was 36.24?and 31.38 C in the heating and cooling procedure,respectively.Adsorption experiments for UTB,the adsorption amount of UO22+reached 123.26 mg/g at 45?(>PCT),and the desorption rate was 97.38%by simply washing with water at 20 C(<PCT).After repeating the adsorption-desorption procedure for 5 times,the adsorption amount and desorption rate kept at 112.56 mg/g and 94.28%,respectively.The maximum theoretical adsorption capacity of UO22+was 172.41 mg/g.The kinetics of adsorption and adsorption isotherms could be well presented according to the pseudo-second-order equation and Langmuir equation,respectively.In the mixtures containing metal ions(UO22+,Mn2+,Ca2+,Mg2+,Fe3+,Pb2+,Cd2+,Zn2+,Cu2+),the adsorption capacity for UO22+was 111.39 mg/g,while that for other ions was 0-8.92 mg/g.The desorption rate of UTB for UO22+was 97%,that for the other ions was 0-3.75%.After the UTB adsorbent passed 20 L of natural seawater,the average U022+recovery from natural seawater reached 117.41 ug-U/g-Ads.The results showed UTB had excellent selectivity and desorption to the template UO22+.4.The gradient heating procedure(40? 1 h,50? 1 h,60? 1 h,70? 3 h)was adopted to successfully fabricate the UO22+imprinted thermosensitive material(CUIm)from chitosan with UO22+as the template and NIPAM as the monomer.The gradient heating process was as follows:the ratio of CS to the amount of NIPAM(mol:mol,1:4),0.01 mg/mL of UO22+concentration.The PCT of UTB was 35.09? and 26.70? in the heating and cooling procedure,respectively.Adsorption experiments for CUIm,the adsorption amount of UO22+reached 144.80 mg/g at 65?(>PCT),and the desorption rate was 94.75%by simply temperature change at 20?(<PCT).After repeating the adsorption-desorption procedure for 5 times,the adsorption amount and desorption rate maintained at 135.39 mg/g and 90.14%,respectively.The maximum theoretical adsorption capacity of UO22+was 225.28 mg/g.The kinetics of adsorption and adsorption isotherms could be well depicted according to the pseudo-second-order equation and Langmuir equation,respectively.In the mixtures containing metal ions(UO22+,Mn2+,Ca2+,Mg2+,Fe3+,Pb2+,Cd2+,Zn2+,Cu2+),the adsorption capacity for UO22+was 105.69 mg/g,while that for other ions was 2.53-10.93 mg/g.The desorption rate of CUIm for UO22+was 93.04%,that for the other ions was 0-12.25%.After the CUIm adsorbent passed 20 L of natural seawater,the average UO22+recovery from natural seawater reached 98.63 ug-U/g-Ads.The results showed CUIm had good selectivity and desorption to the template UO22+. |
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