A common solid waste – corrugated-paper packaging boxes – was carbonized at 300, 450, and 600ºC to develop low-cost adsorbents (biochars). The resulting adsorbents were characterized and their adsorption performances were evaluated by the batch sorption of aqueous Pb(II), Zn(II), Cd(II), and methylene blue (MB). The biochar obtained at 600ºC exhibited larger specific surface area, higher mineral contents, and pH of zero point charge (pHPZC). Calcium carbonate, lead carbonate/basic, and zinc carbonate were observed in the metal-sorbed biochars by a power X-ray diffractometer (XRD). The biochar of higher pyrolysis temperature (600ºC) had high sorption capacity of aqueous Pb(II), Zn(II), and Cd(II) with the Langmuir maximum sorption capacity of 458, 146, and 10.7 mg g^-1, respectively. The pseudo-second-order model gave a better fit for the kinetic data of Pb(II), Zn(II), Cd(II), and MB onto the biochar (600ºC). Moreover, the electrostatic attraction was the dominant mechanism for adsorption of MB while precipitation could be the main mechanisms for adsorption of Pb(II), Zn(II), and Cd(II). Therefore, carbonization can be an efficient and value-addition method for the recycling of waste corrugated paper packaging boxes and for the low-cost wastewater treatment.