Synthesis of cellulose nanofibrils modified with carbon dots-graft-polyacrylamide/ZIF-8 composite hydrogel for simultaneous adsorption and detection of tetracycline

To address the pollution of antibiotics in water resources, a novel cellulose nanofibrils modified with carbon dots-graft-polyacrylamide/Zeolitic imidazolate framework-8 composite hydrogel (CZCH) was synthesized in this study for simultaneous adsorption and detection of tetracycline (TC). The morphology, structure, fluorescent properties, and adsorption and sensing capabilities of CZCH were comprehensively characterized using various analytical techniques. The results demonstrated the CZCH's remarkable adsorption capacity for TC that reached a maximum of 810.36 mg/g. The Langmuir model provided an excellent fit for the adsorption isotherm, while the pseudo-secondary model accurately described the adsorption kinetics. Thermodynamic analysis revealed that the adsorption process was characterized by an endothermic reaction. Impressively, the CZCH maintained 85.6% retention of its initial adsorption capacity even after undergoing five consecutive adsorption/desorption cycles. Moreover, the synthesized CZCH exhibited blue fluorescence with an absolute quantum yield of 5.1%, enabling selective and efficient detection of TC with a low limit of detection of 0.09 μg/L. Furthermore, the mechanism underlying the adsorption and detection of TC by CZCH was elucidated. Cost analysis confirmed that CZCH had a significantly lower cost of CNY 0.07 per gram of TC removal compared to activated carbon, which costs CNY 5.74. Thus, this study presents a sustainable approach for synthesizing a low-cost and multifunctional adsorbent that can be employed for the adsorption and detection of antibiotics.