Comprehensive study of adsorption properties of ultrathin g-C3N4
HE Xiaomiao1， WU Jing2， JIANG Jizhou1,2， LI Ziyan1， ZOU Jing1
(1.School of Environmental Ecology and Biological Engineering/School of Chemistry and Environmental Engineering， Wuhan Institute of Technology， Wuhan 430205， China；2. Key Laboratory of Rare Mineral， Ministry of Natural Resources， Geological Experimental Testing Center of Hubei Province， Wuhan 430034， China)
Abstract：Adsorption has the advantages of easy operation， high efficiency and reproducible adsorbent， and is generally considered as one of the most effective methods for removing industrial dyes. In this paper， bulk g-C3N4 was prepared from melamine by thermal polymerization， and ultrathin g-C3N4 was fabricated by thermal exfoliation， thus obtaining primary exfoliated g-C3N4 and secondary exfoliated g-C3N4 samples. The morphology， composition and structure of the exfoliatied g-C3N4 were characterized by TEM， AFM， XRD， DRS and BET. The effects of temperature， pH， initial concentration and adsorption time on the adsorption performance of ultrathin g-C3N4 were also explored. The results showed that the maximum adsorption capacity of 50 mg bulk g-C3N4， primary exfoliated g-C3N4 and secondary exfoliated g-C3N4 on 90 mg·L－1 organic dye Rhodamine B (RhB) and 100 mg·L－1 Congo red (CR) were 7.270 mg·g－1， 5.207 mg·g－1； 20.463 mg·g－1， 20.909 mg·g－1； 36.094 mg·g－1， 50.375 mg·g－1， respectively. Especially in the primary exfoliated g-C3N4 adsorption systems， the Freundlich isotherm equations for adsorption of RhB and CR are ln qe ＝ －0.93＋0.87ln ce (R2＝0.90) and ln qe ＝ －0.09＋0.73ln ce (R2＝0.97)， respectively. Moreover， it was found that RhB adsorption is subject to the peseudo-first-order kinetic model： ln (qe－qt) ＝ －0.04t＋3.3 (R2＝0.93) and CR adsorption is subject to the peseudo-second-order kinetic model： t/qt＝0.07t＋0.14 (R2＝0.99). First-principles calculations indicated that the different adsorption kinetic models of ultrathin g-C3N4 to RhB and CR are mainly caused many microscopic differences on the aspects of adsorption sites and adsorption energy on the surface of g-C3N4， due to the different molecular structures， different front-line orbits， and different surface electrostatic potentials of RhB and CR. This work will provide new horizons for the adsorption， detection， and degradation of environmental pollutants by two-dimensional material.
2021, Vol. 55 
