Study on adsorption of Cu~(2+) in wastewater with bentonite

The effects of removal rate and adsorption capacity on different adsorption conditions were investigated.The results show that the adsorptions of both Na-bentonite and Ca-bentonite strongly depend on the pH,initial concentration and adsorbent amount.At lower pH values,the mechanisms that govern the adsorption behavior of bentonites are competition of the metal ions with the H+.The basic mechanism is an ion exchange process while the pH values range from 3 to 7.At higher pH values(more than 8.3),formation of copper hydroxyl species may result either participation to the adsorption or precipitation onto the bentonites.Increasing initial metal ion concentration led to the decrease of removal rate and increase of unit adsorption of adsorbent.While Cu2+ initial concentration is 40mg/L,Na-bentonite has the removal rate of 98.4% for Cu2+and Ca-bentonite has the removal rate of 81.2%,respectively.The maximum adsorption capacity of Na-bentonite for Cu2+ is 26 mg/g and Ca-bentonite is 12 mg/g.