IP: 176.224.57.148 On: Fri, 13 Sep 2019 10:55:32 Copyright: American Scientific Publishers Delivered by Ingenta RESEARCH ARTICLE Copyright © 2018 American Scientific Publishers All rights reserved Printed in the United States of America Journal of Computational and Theoretical Nanoscience Vol. 15, 3102–3108, 2018 Biosorption of Zinc(II) and Cadmium(II) Using Ziziphus Spina Stones Eman A. Assirey 1 ∗ , Shadia M. Sirry 1 , Hayfaa A. Burkani 1 , and Medhat Ibrahim 2 1 Chemistry Department, Taibah University, 4744 Medinah, Kingdom of Saudi Arabia 2 Spectroscopy Department, National Research Centre, El-Buhouth Str., 12622 Dokki, Giza, Egypt Environmental pollution with heavy metals is among the most serious environmental problems nowadays. Therefore, the aim of the study is to investigate the efficiency of one of agriculture by- product raw Ziziphus spina stones (ZSS) in the metal ions removal from aqueous solution. Fourier transform infrared (FTIR) and Thermogravimetric (TG-DTG) analysis were used to characteristic its functional groups and thermal stability. Batch method was used to investigate the optimal operating conditions for biosorption process, such as contact time, pH, sorbent dose, sorbent particles size and initial metal ions concentration. Equilibrium data of biosorption for Zn(II) and Cd(II) ions on raw ZSS followed Langmuir isotherm model. Based upon FTIR results the mechanism of interaction is indicated Zn(Cd) is hydrated then interacted with two hydrogen bonding of two carboxyl groups. Then, the Mechanism is introduced with B3LYP/6-31g(d,p) model. Keywords: Ziziphus Spina Stones, Agriculture By-Product, Biosorption, Metal Ions, B3LYP/6-31g(d,p). 1. INTRODUCTION Heavy metals are becoming a severe threat to human health and ecosystem through polluting water, air and soil. 1 Increasing of industrial activities effluents is the main source of heavy metals pollution into various segments of the environment including water, air, soil and biosphere. 2 Some heavy metals are necessary as nutrients for biolog- ical systems in micro levels such as Mn, Ni, Zn, Cu, and Co. 3 4 But high concentrations of heavy metals are able to produce toxic effects. 4 Most of them are carcinogenic and pose several health problems such as reduced growth, impairment of nervous system and oxidative stress. 2 Also they have effect on plants growth and on microscopic organisms in the soil. 3 Heavy metals are not biodegradable like organic contaminants, and they can accumulate in the living organisms. 5 6 Therefore, it is necessary to remove or minimize them to allowable amount to protect the envi- ronment and public health. 6 7 There are different methods for removing or mini- mizing heavy metal ions from aqueous solutions such as chemical, physical and biological techniques. These conventional methods include (ion exchange, filtration, chemical precipitation, membrane technologies, electro- chemical treatment, adsorption on activated carbon, photo- catalysis and evaporation). 4 8 9 They have their advantages ∗ Author to whom correspondence should be addressed. and limitations such as producing large amount of sedi- ment, requiring high costs for operation and maintenance. On the other hand, adsorption method using biomasses (biosorption) may not be as effective as some of the physicochemical approaches, but they are economic, envi- ronmental friendly, and they have excellent performance for removal of metal ions even from very dilute solutions. 9 Biosorption is a promising method for heavy metals removal from aqueous solutions; it is a process, which rep- resents a biotechnological innovation as well as a cheap materials. 4 10 This process, considered as an alternative technique for the removal of heavy metal and metalloid ions, for the treatment of wastewater. 4 Biosorption pro- cess consists of solid phase (biosorbent) and a liquid phase (solvent) that contains the species of interest that will be adsorbed. 2 11 It has been defined as the ability of certain biomaterials to bind and concentrate the species of interest or other species from aqueous solutions onto their surface. 4 There are many mechanisms of biosorption involving com- plexation, chelation, chemisorption, adsorption on surface and pores by physical forces and ion exchange. 2 11 The high affinity of biosorbents towards metal ions refers to the surface chemistry, which consists of different functional groups like alcohol, ether, ketones, aldehydes, carboxylic and phenolic. 2 12 These functional groups are capable to bind heavy metal ions by substitution of hydrogen ions with metal ions in solution, or by forming complexes with the metal ions in solution. Furthermore, Ziziphus spina 3102 J. Comput. Theor. Nanosci. 2018, Vol. 15, No. 11/12 1546-1955/2018/15/3102/007 doi:10.1166/jctn.2018.7676