Removal of Lead(II) Ions from Industrial Waste Water using Biomaterials of Terminalia ivorensis Plant and its Composite with Fe-Alginate Beads as Adsorbents

Three effective adsorbents are developed for the removal of lead ions from industrial effluents basedon stem powder of Terminalia ivorensis (TISP), its active carbon (TIAC) and a composite of Fe-alginatebeadsdoped with the active carbon (TIAC-beads). The beads are synthesized by crosslinking theNa-alginate with Fe3+ instead of conventional Ca2+, with an aim to improve its adsorptivity. Theconditions for obtaining the uniform beads with good morphology are established. These sorbents areinvestigated for their adsoptivity for Pb2+ ions with respect to various extractions conditions and areoptimized for the maximum removal of Pb2+. The sorption capacities are found to be: 34.0 mg/g forTISP, 39.0 mg/g for TIAC and 49.0 mg/g for TIAC-beads. The higher sorption of TIAC-beads may bedue to the cumulative sorption nature of active carbon assisted by iron-alginate beads towards Pb2+.The optimum conditions are: for TISP: pH: 5, sorbent dosage: 2.0g/and, eqi. time: 120 min; for TIAC:pH: 7, sorbent dosage: 1.5 g/L; eqi. time: 90 min; and for TIAC-beads: pH: 6, sorbent dosage: 1.0 g/Land eqi. time: 60 min. Substantial removal of Pb2+ is noted in a range of pHs: 4 to 9 for TIAC-beads;4 to 8 for TISP and 6 to 8 for TIAC. This permits the applicability of the sorbents in neutral as well asless acidic and basic solutions and it is a good feature as Pb2+ containing industrial effluents areinconsistent in their pHs. Three fold excess of co-ions marginally interfered. Thermodynamic studiesreveal that the adsorption is endothermic and spontaneous. The high ΔH values, > 30.0 KJ/mol,emphasizes the chemical nature of binding between Pb2+ and surface functional groups of sorbent andis increasing in the order: TISP (32.385 KJ/mol) < TIAC (35.531 KJ/mol) < TIAC-beads (42.480KJ/mol). This is supported by symmetrical humps with in the curves of pH vs. % removal. Positive ΔSvalues reflect disorder at the solid-liquid interface-an ideal condition for Pb2+ ions to cross the surfacebarrier existing at the solid/liquid interface, resulting in good adsorptivity. Negative ΔG values indicatethe spontaneity of the sorption process. Spent TISP/TIAC/TIAC-beads can be regenerated and reusedfor 2 cycles for TISP, 3 cycles for TIAC and 3 cycles for TIAC-beads. The sorbents are successfullyapplied to remove Pb2+ form industrial effluents.