Adsorption of bisphenol A on lignin: effects of solution chemistry

Adsorption of bisphenol A on a lignin isolated from black liquor, a\nwaste product of the paper industry, was investigated to assess the\npossibility of using the lignin to remove bisphenol A from waters.\nEffects of pH, ionic strength, heavy metals, and dissolved organic\nmatter (DOM) on adsorption were examined. Adsorption equilibrium was\napproached within 5 h. The adsorption capacity of bisphenol A on lignin\nwas as high as 237.07 mg/g. Ionic strength had no influence on the\nadsorption, while higher pH above 7.5 inhibited bisphenol A adsorption\ndue to the repulsive electrostatic interaction between bisphenolate\nanion and the negatively charged lignin surface. The presence of heavy\nmetals of copper and lead increased the adsorption by 11.90 and 26.80\n%, respectively, possibly through modifying the physiochemical\nconfiguration characteristics of labile fraction of the lignin and\nreducing the polarity of it. No obvious impact of DOM on the adsorption\nwas observed. The results of this study suggest that lignin is a\npromising adsorbent material to remove bisphenol A in wastewater\ncontaining complex components such as heavy metals and DOM,\nparticularly at acid and neutral conditions.