Evaluating the Activated Carbon Prepared from walnut in Removal of Arsenic from Aqueous Solution

Arsenic is considered as a heavy metal and toxic pollutants because of its potential harm to human health and environment protection. One of the mechanisms for arsenic removalfrom an aqueous solution is the adsorption process. the aim of this study was to evaluate arsenic adsorption from aqueous solution using activated carbon provided from walnut.
This was an experimental study. At first, the walnut was synthesized and was produced the adsorbent. Stock solution of arsenic was prepared (20, 40, 60, 80, 100, 120 and 140 mg/L). According to the Jar test by rapid mixing (7hr at 120 rpm) for evaluating the reaction kinetic and by slow mixing for evaluating the reaction stability (24 hr at 90 rpm), the effect of influencing parameters on adsorption process such as pH (5.5, 6.2, 6.9, 7.6 and 8.3), adsorbent dosage (10, 20 and 30 mg/l) and initial arsenic concentration (20, 40, 60, 80, 100, 120 and 140 mg/L) were evaluated. Also, to describe the experimental data, the Langmuir, Freundlich, were assessed. All experiments were conducted twice and the mean of percentage removal was obtained.
According to the Langmuir model, the maximum adsorption capacity of the activated carbon provided from walnut 3.15 (mg/g) were obtained. According to the Freundlich model, the maximum adsorption capacity of the activated carbon provided from walnut 2.05 (mg/g) were obtained. The results showed that increase in adsorbent dosage and decrease in pH increased the adsorption of arsenic. While increase in pH and initial arsenic concentration decreased arsenic adsorption.
activated carbon provided from walnut with regards to waste walnuts and found largely in many areas in Iran and low-cost synthesizing could be used to as adsorbent of arsenic adsorption.