The physico-chemical properties and sorption potentials of snail shell particulates, chitin, chitosan, and oxalic acid modified chitosan from <i>achatina fulica</i> shell

Abstract

The purpose of the research was to compare the properties of snail shell particulate (SSP) and its derivatives to those of commercial chitosan (CC) as potential adsorbents. Chitin (CT) was synthesized by deproteinizing and demineralizing SSP with dilute sodium hydroxide (NaOH) and hydrochloric acid (HCl) solutions, respectively. Chitosan (CH) was prepared by partially deacetylating CT with concentrated NaOH. The extracted CH was modified with 10.00% (w/v) oxalic acid (CH_ox). Energy dispersive X-Ray (EDAX), Fourier transform infrared (FTIR), Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM), and chromium adsorption were used to characterize the materials. FTIR spectra of CT and CH materials showed the presence alkyne, nitrile, primary and secondary amines/amides groups with 83.98% as the degree of deacetylation. The spectra of EDAX of CT and CH samples showcased predominant peaks, which correspond to calcium, oxygen, yttrium, and silver. SEM images showed tight, porous, and fractured surface for CT and CH materials unlike the snail shell and CC. BET surface area of the adsorbents were in the increasing order of CT&lt;CC&lt;CH_ox&lt;SSP&lt;CH. CH has a greater surface area of 362.32 m²/g and a mesoporosity of 71.41%. However CH_ox with moisture content 1.52%, bulk density of 0.58 g/cm³, ash content (AC) 0.47% and pH 10.24, has better advantage to be used as biosorbent compared to CC with moisture content 1.08%, bulk density of 0.49 g/cm³, AC 0.87% and pH 8.58. CH_ox had a higher chromium adsorption of 80.4 mg/g at a concentration of 150 mg/L, while having a relatively smaller surface area of 325.38 m²/g (68.36% mesoporosity). The potential removal techniques include ionic interaction between chromium ion and functional groups and surface adsorption due to the textural characteristics of adsorbent samples. When compared to CC, snail shell particle and its derivatives are potential good adsorbents.