Cellulose nanocrystals (CNCs) were modified to work as an adsorbent in order to remove nickel (II) from an aqueous solution. The structure and properties of CNCs were characterised using FTIR and SEM. Statistics show that the response surface model approach performs well. Four operational variables were studied: The initial concentration of the Nickel (II) solution in mg/L, the pH, the contact period in minutes, and the adsorbent dose in mg/100 mL. The removal percentage (%) indicatedthe result. After 60 minutes of contact time, a beginning concentration of 50 mg/L, an adsorbent dose of 15 mg, and an initial pH of 2, the adsorption capacity was 300 mg/g. FTIR examination revealed the following functional groups: hydroxyl groups (OH), which peaked around 3300-3500 cm⁻¹, and carboxyl groups (COOH), which peaked around 1700 cm⁻¹.The AAS was used to determine the remaining concentration in the solutions. With maximum removal capacities of 80–98% at initial concentrations of 175–250 mg/L, the results demonstrated that the modified CNCs hydrogel exhibited high Nickel(II) removal efficiencies. It was found that the adsorption process was massively affected by pH. The adsorption capacity is generally larger at lower pH values because protons are more readily available and can compete with nickel ions for adsorption sites. The elimination of Ni(II) ions from the solution is most effective when the pH is kept between 2-5.