The contamination with metal is a serious issue towards environmental and human health consequences because of its poisonous nature and to accumulation affinity via the chain of food. Sugarcane bagasse-biochar was functionalized with alginate to obtain cost-effective bio-adsorbent for the removing Zn2+ and Cu2+ ions from water. SEM XRD patterns, FTIR spectra, surface area analyses were investigated. Kinetics and isothermal adsorption trials were carried out to assess the capacitive adsorption of the engineered biochar. The functionalized biochar showed comparable removal of aqueous Cu2+ and Zn2+ with maximal sorption capacities of 69 and 71 mg/g, respectively, assuming monolayer sorption onto the identical homogeneous sites of biochar. Sorption kinetics showed a good agreement with the Pseudo-second-order and Boyd models. Moreover, Langmuir, Dubinin–Kaganer–Radushkevich (DKR) and Temkin isothermal models were applicable for description of Zn2+ and Cu2+ binding onto the carbonaceous lattice of the engineered biochar. To recapitulate, alginate-biochar composites could be considered as a promising potent biosorbent for effective removal of metal from water.