Bio-compatible low-cost adsorbents for detoxification of aqueous matrix bearing polychlorinated biphenyls (PCBs) and polyaromatic hydrocarbons (PAHs)

Evans E. CHINYERE¹, Modestus N. OKWO-IGWE², Pius O. UKOHA³, Eno-Obong G. NICHOLAS⁴, Nkiru ANI⁵, Anwani SAMUEL⁶, Jude C. OKENWA⁷, Lynda NGUMOHA⁸,Bello SAMPSON⁹, Nnadozie ONYEZEWE¹⁰, and Oge ALUM¹¹

^1,5,6,8,9,10 Department of Chemistry, Alex Ekwueme Federal University, Ikwo, Nigeria

^2,3,4,7,11 Department of Pure & Industrial Chemistry, University of Nigeria, Nsukka

Email: evans.chinyere@funai.edu.ng   chievanseledalachi@gmail.com +2348030999585

ABSTRACT

Two set of adsorbents were prepared: chitosan-silica nano-composite and 4-aminoantipyrine-based functionalized activated carbons. Chitosan was obtained by removal of acetyl groups from chitin using NaOH according to a previously described procedure. Silica was extracted by the placement of coconut husks pieces (100 g) in a silica crucible and heated in muffle furnace for 5 h at 700 oC to obtain coconut husk ash (CHA) which was processed and chemically treated to recover silica nanoparticles. The Silica (1g) was then added to a solution of chitosan (2g) in 100 cm³ acetic acid (2%) and magnetically stirred for 1 h to obtain chitosan-silica nano-composite. It was characterized by FTIR, XRD, SEM/EDX and was found to achieve between 90 and 93% PAHs removal at acidic pH and up to 85.74 % removal of PAHs with increasing dosage. 4-aminoantipyrine based ligand was synthesized by coupling diazotized 1-phenyl-2,3-dimethyl-4-aminopyrazole-5-one and 1H-indole-2,3-dione. It was characterized via ultraviolet visible (UV-vis), infrared (IR) and nuclear magnetic resonance (NMR) spectroscopic techniques. Activated carbons (ACs) were obtained at 250, 350, 400 and 450 oC respectively from phosphoric acid treated samples of the shell of Achatina achatina, egg shell of Gallus gallus, seed shell of Afzelia Africana SM, husk of Arachis hypogaea L, peel of Musa paradisca L, cob of Zea mays L, seed shell of Mucuna urense and peel of Manihot esculentum. The ACs and FACs were characterized using FTIR, SEM/EDX techniques. Twenty two samples of ACs were produced from the agro-based materials at 250, 350, 400 and 450 oC respectively. Twenty two FACs were further obtained after modifications. SEM micrographs of the FACs showed surface corrugation. EDX analysis gave 100, 86.69 and 68.29 % carbon for FACs obtained at 450 oC with the seed shell of Mucuna urense (FACSHMUR45), peel of Manihot esculentum (FACMESC45) and husk of Arachis hypogaea L (FACHGNUT45) respectively. PCBs removal (%) at equilibrium by the adsorbents were in the order 85.35 ± 1.77 > 84.24 ± 2.18 > 77.97 ± 1.59 for FACMESC45, FACHGNUT45 and FACSHMUR45 respectively. Mean (%) PCBs removal was 87.39 ± 1.81, 85.30 ± 1.84, 84.43 ± 3.53, 79.27 ± 2.21 and 76.21 ± 2.16 with 0.6, 0.8, 1.0, 0.4 and 0.2g adsorbent respectively.

                                                                            

Keywords: Adsorbents. Nano-composite. Polychlorinated biphenyls. Polyaromatic    hydrocarbons. 4-aminoantipyrine. Isatin. Chitosan. Silica.

References:

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