The dye concentration in aqueous solution was measured using
absorption in a UV/Vis spectrophotometer (UV-1800, Shimadzu)
at a characteristic wavelength. The maximum absorbance of the
dye was 513 nm. To analyze the surface charge of the adsorbents
at various pH values, the zeta potential of the dried biosorbent was
analyzed with electrophoretic light scattering spectroscopy (ELSZ,
Photal Otsuka Electronics).