For aquatic ecosystems, Hg2+ removal from wastewater is crucial. However, getting high-efficiency Hg2+ extraction is still a challenge due to slow rates and poor selectivity. The active thiosemicarbazide (TSC) chelating units were added to the cellulose (CE) in this work using a novel synthetic pathway. The TSC-CE derivative was then used to produce a Hg2+ ion-imprinted sorbent. Initially, the Michael reaction was used to yield cyanoethyl cellulose (CEC). TSC units were combined by a chemical reaction with the added -CN groups. After Hg2+ was attached to TSC-CE, it was cross-linked with glutaraldehyde before being eliminated via elution with HNO3/EDTA. The Hg2+ imprinted sorbent (Hg-TSC-CE) achieved improved adsorption selectivity for Hg2+ and significantly higher adsorption capacity (qm = 353 ± 0.5 mg/g) in comparison to the non-imprinted sorbent. The FTIR and XPS studies both gave strong evidence supporting the kinetic results for the pseudo-second-order model, which said that coordination is the main process of adsorption. The Langmuir model also well explained the isotherms. It showed that Hg2+ mainly adsorption took place in monolayers, with a pHZPC value of about 5.6. Moreover, the Hg2+ adsorption was endothermic, and the optimum pH was observed at 5.