Kinetics and column adsorption study of diclofenac and heavy-metal ions removal by amino-functionalized lignin microspheres

Abstract

In-depth kinetic and column adsorption study for diclofenac, DCF, heavy-metal and oxyanions adsorption on highly effective amino-functionalized lignin-based microsphere adsorbent (A-LMS) is examined. The A-LMS was synthesized via inverse suspension copolymerization of industrial kraft lignin with the amino containing grafting-agent (polyethylene imine), and an epoxy chloropropane cross-linker. The batch adsorption results indicated process spontaneity and feasibility of a high removal capacity: DCF(151.13)>>Cd2+(74.84)>Cr(VI)(54.20)>As(V)(53.12)>Ni2+(49.42 mg g−1). The quantum chemical calculated interaction energies reveal stabilization of the A-LMS/DCF complex through the electrostatics and van der Waals interactions. The results from the pseudo-second order and Weber-Morris fitting indicate a fast removal rate; thus, column tests were undertaken. The single resistance mass transfer model, i.e. the mass transfer (kfa) and diffusion coefficient (Deff), shows pore diffusional transport as a rate limiting step. The fitting of the fixed bed column data with empirical models demonstrates the influences of flow rate and adsorbate inlet concentration on the breakthrough behavior. Pore surface diffusion modeling (PSDM) expresses mass transport under applied hydraulic loading rates, calculated breakthrough point adsorption capacities: Cd2+(58.1)>Cr(VI)(54.1)>As(V)(50.9)>>Ni2+(42.9 mg g−1)), without performing the experimentation on a full pilot-scale level, further confirms the high applicability of the A-LMS bio-based adsorbent.