Parametric Studies on Descriptive Isotherms for the Uptake of Crystal Violet Dye from Aqueous Solution onto Lignin-Rich Adsorbent

This study investigates (using six error functions criteria) descriptive isotherm models for adsorbing crystal violet dye (CVD) onto lignin extract. The lignin adsorbent (named PTA) was obtained from palm tree trunk and subjected to physiochemical, Fourier transform infrared (FTIR) and scanning electron microscopic (SEM) analyses. Influences of contact time, dose, particle size, initial CVD concentration and temperature were studied. 53.21% lignin yield was recorded for the adsorbent. SEM images and FTIR spectra indicated significant porosity and lignin presence in the PTA. Average relative error, sum of absolute errors and sum of normalized error confirmed Redlich-Peterson and Freundlich isotherms, respectively, as the best linear and nonlinear descriptive models. Gibb's free energy and enthalpy change of -1976.89 and 105.505 KJ/mol, respectively, indicated spontaneous and endothermic process. After four regenerations cycles, PTA showed over 80% removal efficiency.