Characterisation and adsorption properties of calcinated eggshell, salicylic acid-modified eggshell, and 2, 4-dihydroxy benzoic acid-modified eggshell

Abstract

ABSTRACT This study synthesised eggshell waste, an agricultural by-product, into a calcinated porous material modified by salicylic acid as a new and effective adsorbent for remediation of Cu(II) from an aqueous solution. The impregnation of salicylic acid onto the surface of calcinated egg-shell improved the adsorption property of the eggshell. Furthermore, it was found that the salicylic acid-modified egg-shell; (SAL-E) has a highly developed functionalised surface and rich pore property compared to that of calcinated egg-shell investigated by FTIR and BET surface analysis, respectively. Moreover, the surface area of the SAL-E composite was found to be 6.65 m2g−1 which is six times more than the calcinated eggshell; (E-500). The salicylic acid procreated calcinated egg-shell showed the superior adsorption property towards copper heavy metal compared to that of calcinated eggshell and 2,4-dihydroxybenzoic acid-modified eggshell; (DHB-E). The results of the study showed that the Langmuir adsorption of salicylic acid procreated egg-shell was up to 177.74 mgg −1 which is four times more than the calcinated egg-shell; (E-500). The maximum adsorption showed by salicylic acid-modified eggshell; (SAL-E) occurred at pH 7. The efficiency of modified egg-shell for the removal of copper from wastewater is directly related to pH, temperature, and contact time. FTIR spectroscopy study affirmed that the vital functional groups engaged in the uptake of Cu(II) onto the surface of modified – eggshell wastes, were hydroxyl group, carboxyl, carbonyl, and C = C of aromatic ring via Cu(II)−π interaction. FTIR, Raman, and UV – DRS evaluations proclaimed the introduction of functional groups that can be rendered more emplacements for binding of Cu (II). The results of this study displayed that the adsorption accept, the pseudo-second-order, Langmuir isotherm, and intraparticle diffusion, indicating that the adsorption mechanism is a chemical adsorption process and physisorption to some extent. The thermodynamic parameters such as ΔG0, ΔH0, and ΔS0 were estimated for all the porous adsorbent materials.