Adsorption of Cadmium from synthetic wastewater using modified silicon dioxide nanoparticles

Heavy metals such as cadmium causing numerous adverse effects on the aqueous solutions. So the presence of heavy metals in surface water and ground water has become a major inorganic contamination problem. There are several method to remove the heavy metals from aqueous solutions that adsorption is one of the best method. The aim of this study was to evaluate the efficiency of Silicon dioxide nanoparticles modified by 2-aminopyridin and EDTA as adsorbent for the removal of Cd2 ions from aqueous solutions.
Material and Silicon dioxide nanoparticles with toluene put in ultrasonic bath. Then mixture of 2-aminopyridin and EDTA with ratio of 1:1 added to primary solution. After 24 hours reflux on oil bath and 10 minutes centrifuging, sample rinsed by chloroform, ethanol and deionized water. In the end, the product prepared after drying at 100 o C for 24 hours. Experiments were conducted to study the effect of solution pH, temperature, contact time, absorbent amount and initial metal concentration. Experiment conducted in bath system with three replicate. The test solutions of various concentrations were prepared from the stock solution. The solution pH was adjust using 0.1 M HNO3 and 0.1 M NaOH at the beginning of the experiment and not controlled afterwards. Solution containing adsorbate and adsorbent was taken in 250 mL capacity conical flask and agitated at 120 rpm in a shaker at predetermined time intervals. Samples putted on the centrifuge with 4000 rpm for 5 minutes .Lead ions were determined spectrophotometrically by atomic absorption spectrophotometer. Finally for determination of adsorption mechanism, adsorption isotherm models and kinetic models were studied .Results was analyzed by Excel software.
The Results showed that, the highest uptake and optimum conditions was observed in pH=4, contact time 35 minutes and temperature 25℃. The Analysis of Langmuir isotherm (R2=0.93) and Freundlich isotherm (R2=0.94) show that, experimental data were fitting match by both isotherm but it is more fitting match with Freundlich isotherm. Kinetic studies showed that, kinetic of adsorption according to pseudo second order equation (R2=0.99).
Base on the results it can conclude that, modified silicon dioxide nanoparticles could be used as a best adsorbent for the removal of heavy metals from aqueous solutions especially for the industrial wastewaters because of the cost, easy to use, renewable, suitable and environmental friendly. Comparing with other similar studies these were found to be the excellent adsorbents and can be successfully used by Industries for heavy metal removal.