Development of some novel lignin derivatives for adsorptive removal of heavy metals and recovery of precious metals (2006)

DEVELOPMENT OF SOME NOVEL LIGNIN DERIVATIVES FOR ADSORPTIVE REMOVAL OF HEAVY METALS AND RECOVERY OF PRECIOUS METALS by Durga Parajuli Chairperson of the Supervisory Committee: Professor Katsutoshi INOUE Department of Energy and Materials Science, Saga University Lignophenol was prepared from waste wood powder by a phase separation method which involved the immobilization of lignin with phenol followed by separation of cellulose matrix by treating with sulphuric acid solution. Different polyphenolic adsorption gels namely crosslinked lignophenol, crosslineked lignocatechol and crosslinked lignopyrogallol were prepared by immobilizing phenol, catechol and pyrogallol onto lignin and subsequent crosslinking with paraformaldehyde. 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. Crosslinked lignophenol 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, crosslinked lignocatechol exhibited high selectivity for various heavy metals with maximum capacity for Pb(II). During column experiment also it exhibited efficiency, recyclability and stability. In addition, the crosslinked lignophenol gel was further functionalized with ethylenediamine and primary amine groups to get EN–lignin and PA–lignin, respectively. They were found be selective for Au(III), Pd(II) and Pt(IV) possessing very high adsorption capacity for Au(III) and almost no adsorption for other metal ions like Cu(II), Sn(IV), Fe(III), Ni(II), Zn(II) and so on that are commonly occur together with precious metals. Also, EN–lignin was found to have adsorption ability for some heavy metal oxyions like vanadates, tungstate and molybdate. In all cases, the gels were found to be superior to activated carbon in selectivity in effective separation and recovery of precious metals. While using un-crosslinked lignophenol for adsorption of Au(III), beautiful gold microplates of hexagonal or triangular symmetry were observed. Thus, by the present study, novel uses of wasted wood material have been found in the form of low cost, environment friendly, biodegradable and convenient lignin based adsorption gels which can be effectively applied for separation and recovery of precious metals and removal of heavy metals from industrial effluents. DEVELOPMENT OF SOME NOVEL LIGNIN DERIVATIVES FOR ADSORPTIVE REMOVAL OF HEAVY METALS AND RECOVERY OF PRECIOUS METALS by Durga Parajuli A thesis submitted in partial fulfillment of the requirements for the degree of Doctor of Engineering Faculty of Science and Engineering Department of Energy and Materials Science SAGA UNIVERSITY Approved by __________________________________________________ Prof. Katsutoshi INOUE Supervisor __________________________________________________ Prof. Tohru MIYAJIMA __________________________________________________ Prof. Takanori WATARI __________________________________________________ Assoc. Prof. Keisuke OHTO Program Authorized to Offer Degree _________Doctor of Engineering _____________