DEVELOPMENT OF LIGNIN DERIVATIVES FOR THE RECOVERY AND REMOVAL OF METALS

Lignin based adsorption gels namely crosslinked lignophenol (CLP), crosslineked lignocatechol (CLC) and crosslinked lignopyrogallol (CLPy) were prepared by immobilizing phenol, catechol and pyrogallol onto lignin of wood powder and subsequent crosslinking. The study of adsorption behavior of the gels for some precious and base metals revealed that they were highly selective for Au(III) with competitive adsorption capacity. CLP exhibited outstanding selectivity for Au(III) since it was almost inert towards other metals. Furthermore, it reduced Au (III) to Au(I) and finally to elemental gold making it easier for recovery. On the other hand, CLC exhibited high selectivity for various heavy metals with high efficiency, recyclability and stability. In addition, CLP was further functionalized to EN– lignin, PA–lignin, and DMA-lignin. The derivatives show high selectivity for Au(III), Pd(II) and Pt(IV) with high loading capacity and almost no adsorption for other metal ions. Thus, by the present study, novel uses of wasted wood material have been developed in the form of economic & environment friendly adsorption gels.