Abstract

Removal of the Ni (II) metal ions from aqueous solution was carried out using citric acid modified Annona
squamosa bark powder. The modified biosorbent was characterized by Fourier transmission infrared, scanning
electron microscope and X-ray difractometer techniques. The effect of solution pH, adsorbent dose, initial
concentration of metal solution, contact time was investigated in a systematic manner. Experimental data were
analyzed by kinetic parameters such as lagergrens pseudo-first order and pseudo-second order models and found
that the biosorption of Ni (II) followed pseudo-second order model by its good correlation coefficient values
which are very close to the unity. The equilibrium data were analyzed by using Langmuir, Freundlich, Dubnin–
Radushkevich isotherm models. Among these isotherm models Langmuir model was fitted well with its good
correlation coefficient and low Chi (χ) values. Desorption and recovery of the adsorbent were carried out using
HCl solution by changing its concentration from 0.001 N to 0.25 N. The results concluded that the modified
A. squamosa bark powder was an efficient, eco-friendly, and economically cheap adsorbent in the removal of
Ni (II) ions from the aqueous medium.