Background:
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.

Material and methods:
A novel polystyrene (4-azo-1')-2'-hydroxy-5'-sulfobenzene (PSAHSB) adsorbent was applied for removal of Ni (II) ions from aqueous solutions under batch conditions . The pH, temperature and contact time parameters studied extensively. The ionization constants of an adsorbent were investigated. The adsorption isotherm, thermodynamics and kinetics were also investigated. Both the pseudo-kinetics were examined.

Results:
The adsorption increased in the pH range of 1–3, then remained at a higher level for the pH range of 3–7.5, but decreased at pH large than 8, which demonstrated that the adsorption was affected by pH. The adsorption capacity was increased with the temperature rising. The adsorption equilibrium time was 20 min. 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 exhibits excellent stability and high regeneration .

Conclusions:
The absorbent can be used efficiently for treatment of Ni+2 ions from naturally- occurring and industrial materials.