Acid/base Treated Spent Black Tea Characterization of Functional Groups and Lead Sorptive Mechanism

Surface modification of raw biomass directs an attractive approach for improvement of heavy metal uptake from aqueous solutions. Spent black tea was modified with NaOH and HNO3 and effects of surface modifications on the properties of the sorbent were studied by Fourier transform infrared spectroscopy and acidic/basic sites study by Boehm method. NaOH causes an increase in the content of carbonyl and hydroxyl groups, while the HNO3 treatment results decrease in the amount of single-bonded oxygen functional groups such as phenols, ethers, and lactones and significant decreases in the Lead adsorption noted, while the NaOH treatment slightly increased the Lead uptake. The Pb(II) ions adsorption increased mainly due to the enhancement of carbonyl functional groups of esters and amide in the base hydrolysed biomass. FTIR analysis of native and chemically treated sorbent impacts different active sites for fixation of Pb was observed. A comparison of four isotherm models of Langmuir, Freundlich, Flory-Huggins and Dubinin-Radushkevish revealed that the Langmuir and F-H isotherm model are in good agreement with the experimental data and the Kinetics of sorption follows the pseudo second order model.