Chemical and Phase Characterization of Snail Shell (Archachatina Marginata) as Bio-Waste from South-West in Nigeria for Industrial Applications

This paper aimed at characterizing waste snail shells found in South-West, Nigeria for potential industrial applications. Snail shells which represent the bio-shell waste of snails' remnants from restaurants, eateries or snail sellers constitute a serious degree of environmental threat with little or no economic value; their effective utilization can bring immense economic prosperity. Snail shells were obtained from two selected region of South-Western part of Nigeria. The obtained snail sells were thoroughly washed to remove adhered dirt and later dried in an electric powered oven at 110 o C for 6h. The dried shells were then crushed and further pulverized to obtain powder snail shells (SS p ) and labeled samples SS p A and SS p B respectively. The chemical composition of the samples was determined by Energy dispersive X-ray (SEM/EDX) while the phase constituent was analyzed using X-ray diffractometer. The results showed that SS p A consist mainly calcium (Ca) 83.38% while sample SS p B contains higher calcium (Ca) content of 85.04%. However, X-ray diffraction (XRD) indicate predominant phase of calcite for the samples. This indicates that the snail shell powder is suitable for industrial applications such as filler in paper and ceramic industry. Keywords: Snail shell; chemical composition; phase constituent; calcite phase. DOI: 10.7176/CMR/12-6-03 Publication date: July 31 st 2020

strength of the material. The use of snail shell powder in treatment of water has been reported [8]. There is need to characterize snail shell to be able to determine the chemical composition present for its industrial application.

Materials and method 2.1. Material
The main starting material used in this work is snail shell. The snail shells used in this work are of the Archachatina Marginata species and were obtained from Ilaje, Ondo State and Errufun Village, Ado-Ekiti, Ekiti State both from South-Western region in Nigeria. Figure 1 shows a pictorial representation of the snail shell sample. Snail shells collected from Ilaje, Ondo State was labeled Sample SSA while the shells obtained from Ado Ekiti, Ekiti State was labeled sample SSB. The as-received snail shells were initially washed thoroughly with water to remove adhered dirt, and then dried in an electric oven at 110 o C for 6 h. The dried shells were then crushed using porcelain lined mortar and pestle. The crushed shells were then pulverized using electrically powered laboratory pulverizer to obtain powdered snail shells SSpA and SSpB respectively. The powdered shells were then sieved using a 74µm sieve to obtain a fine powder which was used for this work. Figures 2 (a -b) show the powdered snail shells respectively.

Characterization
The microstructure evaluation was examined using scanning electron microscope with attached energy dispersive spectrometer (SEM/EDS, ASPEX 3020) while the chemical composition was examined by Energy Dispersive Xray fluorescent (XRF-Pananalytical, minipal 4). The XRD analysis of the snail shell powder was carried out using an Empyrean X-ray diffractometer DY 674 (2010) with 40mA, 45VA and 240mm tube current, voltage rating and goniometer radius, respectively

Microstructure/elemental composition (SEM/EDS)
The results of the microstructure evaluation and the elemental composition of the snail shell powders (SSpA and SSpB) conducted by Scanning electron microscopy with attached Energy dispersive spectroscopy (SEM/EDS) is presented in Figures 3 (a) and (b) respectively. It is observed that both samples displayed similar microstructure revealing a somewhat fibrous morphology. The dark features observed at the surface might be due to the presence of carbon strands. This similar feature has been reported by Kolawole et al. [9]. However, the ED spectrum shows that both SSpA and SSpB predominantly contain calcium while others element such as Carbon, Potassium, Oxygen, Magnesium, Sulfur, Sodium, Aluminum and Silicon are in traceable amounts.   Table 1 shows the result of the oxide composition of the samples using the Energy Dispersive X-Ray Fluorescence (XRF) analysis while Figures 4 (a -b) indicate the EDX spectrum of the samples SSpA and SSpB respectively. The result confirmed the presence of K2O, Fe2O3, CaO, P2O5, Al2O3, ZnO and SrO with CaO, Cr2O3, TiO2 and MnO as the major constituents of the snail shell sample. This however confirmed the results obtained in Figures 3  (a -b). It can be observed from Figure 4a that the concentration of CaO of Sample SSpA is at its peak (173730 cps/mA) and that of sample SSpB in Figure 4b was at the peak (152962cps/mA), this was similar to that obtained by previous researchers [10].

Phase composition
The results of the phase composition investigated by X-ray diffractometer is presented in Figures 5 (a) and (b). The XRD pattern obtained revealed that the diffraction peaks are 26.8660°and 36.6856° and their inter-planar distance is 3.31585Å and 2.44974Å with a relative intensity of the X-ray scattering of 100.00 and 100.00. The phases at these peaks are aragonite and calcite with a score of 27 and 25, respectively. The presence of these minerals in the shell forms the bases of the hard nature of the shells.

Conclusion
The concentration of CaO in both samples was at the peak 83% and 81% respectively, it was also observed that the concentrations of the metals were in decreasing order: Ca> K > Na > Mg > Fe > Zn in both samples. Some useful elements present in snail shell powder shows that the snails shell powder can be used in industries as fillers, an additive in the production of toothpaste, mineral supplement as well as cement, mortar, glass, plastics, acetylene gas, insecticide and water treatment agents due to the presence of calcium oxide.