The Philippine mining industry has been continuously contributing to water pollution by the improper discharge of toxic effluents. Pagatban River in Southern Negros is one of the outcomes of such, due to copper contamination. Major drawbacks presented by conventional treatment methods demand an alternative which uses waste materials in the process of biosorption. This study extended the development in the aforementioned area by producing competent biosorbent nanoparticles in Pristine (PB), Alkali (NaOH) modified (AB), and Carbonized Forms (CB) from Calamansi (Citrus microcarpa) peels for Copper removal. Biosorbents were prepared by drying, grinding, sieving, and modifying the peels. Assessment by batch biosorption followed 0.5g:50 ml biosorbent-to-water ratio in 60 mins of agitation; Water samples were then analyzed using Flame Atomic Absorption Spectroscopy and a pH meter. Both in biosorption (%) and pH, all biosorbents were significantly different: AB showed the best results with means of 95.70% and 6.51, respectively, followed by PB (78.57%, 4.41) and CB (76.42%, 5.77). The presence of carboxylic acid and carboxylate functional groups and the successful modification of the biosorbents were confirmed by Fourier Transform Infrared Spectroscopy. Field Emission - Scanning Electron Microscopy established the heterogeneous morphologies of quasi-spherical nanoparticles with mean sizes of 65.30 nm, 52.09 nm, and 63.46 nm for PB, AB, and CB respectively. Moreover, predominant biosorption mechanisms recognized were ion exchange and chemisorption, which are potentially reinforced by their nanoparticle-size. Thus, the biosorbents, particularly AB can be utilized for the treatment of copper-bearing wastewaters and facilitate the valorization of C. microcarpa peel wastes.