Herein, we report the synthesis of carbon spheres (CS) using a relatively low-temperature hydrothermal technique using lactose as precursor pre-treated with HCl. The successful synthesis, spherical morphology, porous morphology, and monodispersed nature of CS were confirmed via scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Isoelectric point (IEP) was determined as 3.8, and at neutral conditions the prepared carbon particles are negatively charged at - 43 +/- 2.50 mV. Owing to their spherical morphology, almost uniform distribution and negatively charged surface at neutral conditions, the prepared CS were used as adsorbent for the removal of methylene blue (MB) and Geimsa stain (GS) from aqueous environments at pH 7. It was shown that CS has 97% adsorption capability for GS, whereas for methylene MB, the maximum adsorption capacity was 67% for 0.1-g CS from 50-ppm dye solutions in DI water. The adsorption studies revealed that the Langmuir and modified Fruendlich (MFE) adsorption models resulted in considerably high linear correlation coefficient (r(2)) values and the efficient adsorption of positively charged species on CS can be represented better with the MFE model.