Experimental and Kinetic Studies on Adsorption of Trace Amount of Nickel from Aqueous Solutions Using a New Chelating Adsorbent Polystyrene (4- Adsorbent Polystyrene (4 azo-1')-2'-hydroxy-5'-sulfobenzene -azo-1')-2'-hydrox

Abstract

The modern instrumental analysis methods do not always allow direct
determination of trace amounts of elements due to influence of the matrix
composition of the sample. A novel polystyrene (4-azo-1')-2'-hydroxy-5'-
sulfobenzene abbreviated as PSAHSB adsorbent synthesized based on amino
polystyrene functionalized with chelating azo phenolic groups was applied for
removal of trace Ni (II) ions from aqueous solutions under batch conditions. The
parameters including pH, temperature and contact time on removal of nickel ions
were studied extensively. The ionization constants of an adsorbent were
investigated. The adsorption isotherm, thermodynamics and kinetics parameters
were also investigated. To gain insight into the adsorption kinetics, both the
pseudo-kinetics were examined. The adsorption of trace nickel ions increased
smoothly in the pH range of 1–3, then remained at a higher level for the pH range
of 3–7.5, but decreased sharply at pH large than 8, which demonstrated that the
adsorption was affected strongly by pH. On the other hand, the adsorption
capacity was increased sharply with the temperature rising. The adsorption
equilibrium time could be reached in 25min. The equilibrium data could fit the
Langmuir isothermal model very well, and the thermodynamic analysis suggested
that the adsorption of nickel ions on the adsorbent is a spontaneous and
endothermic process. The results indicated the pseudo-second-order kinetic
model fitted the experimental data better. The adsorbent have three ionization
constants and exhibits excellent stability and high regeneration. The absorbent
can be used efficiently for treatment of Ni+2ions from naturally- occurring and
industrial materials.