Synthesis Of Bamboo-derived Nanocellulose-based Aerogels And Their Adsorption Properties Toward Cd²⁺Ions In Water

At present,the wastewater containing Cd²⁺has imposed a serious threat on the surrounding environment and human health,Adsorption is one of the most popular and effective method for the removal of heavy metals from wastewater,due to wide sources,low cost as well as excellent removal effect.However,many conventional adsorbents?e.g.,activated carbon?in the form of powder suffer from the drawbacks,such as the high cost and difficulty in recyclability and reuse.Therefore,the development of novel and multi-efficiency biomass-based adsorbents with high recyclability and reusability has become an urgent need in the field of current wastewater treatment.In this study,the cellulose nanofibers?CNF?dispersion was isolated through high-pressure homogenization of bamboo pulp that was subject to TEMPO-oxidized pretreatment.Then,use CNF as scaffold materials to fabricate amino-functionalized composite aerogels and thiol-functionalized ones,both of which showed good adsorption abilities for heavy metals as well as the ease of recycling and reuse.The morphologies and microstructure were characterized in terms of FT-IR,BET,elemental analysis,and compression property measurement.Then,effects of CNF/APTMs or APTMs weight ratiosandpH valuesof the solutions on adsorption properties of the as-obtained aerogels were examined.And the adsorption kinetics,adsorption thermodynamics and adsorption isotherms were also studied.Below are the main research findings:?1?With 3-mercaptopropyltrimethoxysilane?MPTs?chosen as an thiol-functionalized agent of CNF,the mechanically durable CNF-SH aerogels with abundant thiol moieties anchored onto the surfaces were prepared by a facile one-step freeze drying.The results showed that the weight ratios of MPTs/CNF had a certain effect on adsorption properties of the modified aerogels,and it displayed a highly selective adsorption effect toward Cd²⁺ions in the co-existing system containing multiple kinds of heavy metal ions.And its adsorption capacity was superior to that of commercial activated carbon with a very high specific surface area.The whole adsorption process conformed to the pseudo-second-order kinetics and the Langmuir isotherm,suggesting that the adsorption process was dominated by chemical adsorption with a maximum adsorption capacity up to 105.7 mg/g.In addition,the CNF-SH aerogel still exhibited a removal efficiency of Cd²⁺ions as high as 90%after 4 cycles of adsorption-desorption,while the apparent structure of the aerogel was well maintained.?2?With 3-aminopropyltrimethoxysilane?APTMs?chosen as an amino-functionalized agent of CNF,the mechanically durableCNF-NH2 aerogel with abundant amino moieties anchored onto the surfaces was prepared by a facile one-step freeze drying.The results demonstrated that a certain effect of APTMs/CNF weight ratios was noted on adsorption properties of the modified aerogels(not clear,try this:the removal of Cd²⁺by the modified aerogels were improved with the increase of APTMs/CNF weight ratio).In addition,pH values and temperature of the solution also had a pronounced effect on the adsorption capacities.The whole adsorption process conformed to the pseudo-second-order kinetics and the Langmuir isotherm with an implication that the adsorption process was dominated by chemical adsorption with a maximum adsorption capacity up to 118.3 mg/g.