This study is based on the concept of sustainable development, focusing on the valorization of plant waste as a renewable resource for cellulose extraction. The extracted cellulose can be used for biomaterial production and in wastewater and soil salinity treatment. The objective of this work is to synthesize a polyelectrolyte biopolymer by enhancing the hydrophilic character of extracted cellulose (EC) from barley straw. This is achieved by introducing carboxylate groups through the grafting of citric acid (CA). The macromolecular mass of the extracted cellulose was determined by viscometry. Esterification of EC with citric acid results in the formation of cellulose citrates (MBSC), which incorporate a significant number of hydrophilic carboxyl groups. The synthesized copolymers were characterized using thermogravimetric analysis (TGA), Fourier Transform Infrared Spectroscopy (FTIR), viscometry, and potentiometry. Results indicate that MBSC structures vary depending on the extraction method, temperature, treatment duration, and degree of substitution (DS). The influence of esterification temperature and reaction time on DS was also studied, with the highest DS value of 0.36 observed after 20 minutes of treatment at 160 °C.