Carbon nanotubes (CNTs) are engineered particles (i.e., particles in the size range of 1–100 nm) that are widely used in electronics, optics, aerospace, medical, and industrial applications. With a wide range of known toxic effects, CNTs are considered as emerging contaminants of concern requiring their control in the environment such as in water media. However, the fate and transport of the CNTs in the environment are expected to depend on many complex parameters including chemistry and conditions of the environmental media. To understand the fate and transport and hence to control them in the water media, the effect of water pH (2-12) on the CNTs structural properties, specifically multiwalled carbon nanotubes, was evaluated using spectrometric measure. The highest absorbance was noticed in the pH 10 solution. The higher absorbance could indicate tighter structures, because nanotubes could have assembled into tighter hexagonal structures, increasing its tensile strength. Also, the higher absorbance is potentially caused by higher solubility of the CNTs in the water at pH 10.