This studied aimed to remove Cu (II) from waste water onto the modified cellulose nanocrystals using the Box-Benken design in RSM. The Cellulose nanocrystals derived from waste paper was characterized and compared with the modified cellulose nanocrystals by FTIR. The adsorption peaks 3367 and 3420 found in the modified CNC and unmodified CNC spectra, respectively, revealed the characteristics for the stretching of –OH found in the polysaccharide. The strong absorption peak 1551 was found to be present in the unmodified spectra, confirming the characteristics of the asymmetric and symmetric of CO in COO-, and giving evidence for the successful incorporation of EDTA and cellulose nanocrystals. Four parameters pH, contact time, initial concentration and adsorbent dosage were optimized with the use of response surface methodology (RSM) with a quadratic model box-Benken design. Twenty-nine experimental runs were conducted to get the desired response. The results showed that CNCs effectively removed Copper (II) ions, with a maximum removal efficiency of 99.78%. The optimised conditions were pH 6, initial Cu (II) concentration of 125mg/L adsorbent dosage of 6 mg/200mL, and contact time of 30 minutes. The quadratic model developed through RSM showed a moderate to strong correlation, with an R-squared value of 0.988, indicating that 98.88% of the variation removal efficiency can be explained by the predictor variables and their interactions. This study demonstrates the potential of CNCs as an eco-friendly adsorbent for heavy metal removal and highlights the effectiveness of RSM in optimising adsorption processes.