Calcium/iron-layered double hydroxides-sodium alginate for removal of tetracycline antibiotic from aqueous solution

Abstract

The current work is to produce the new adsorbent from chicken eggshells wastes which support the efforts directed to reuse such wastes to achieve the sustainable concepts. Calcium ions have been extracted from eggshells and mixed with iron under best conditions to prepare nanoparticles of calcium / iron (Ca/Fe)-layered double hydroxides (LDHs). The nanoparticles must be immobilized using sodium alginate to obtain the spherical particles named (Ca/Fe)-LDH-sodium alginate beads that tested for eliminating of tetracycline (TC) antibiotic from aquatic environment. The proper conditions for manufacturing of mentioned beads were molar ratio of (Ca/Fe) = 1, pH 12 and nanoparticles dosage = 6 g/ 100 mL. To ensure the TC removal efficiency ≥ 95 %, sorption tests must be agitated at time 90 min, pH 7, 200 rpm and beads dosage 1.2 g/ 50 mL for initial concentration (Co) 100 mg/L. Langmuir isotherm and Pseudo second order have acceptable ability in the description of such tests with highest sorption capacity of 10.393 mg/g. The formation of nanoparticles in the manufactured beads was proved by the characterization tests. Also, the increase of carbon (C) and nitrogen (N) in the beads beyond interaction with polluted water confirms the occurrence of antibiotic sorption.