Abstract:
Effects of attapulgite and sepiolite adsorbing Cd
2+ in aqueous solutions relative to initial concentration, solid-liquid ratio, exposure duration, and pH were investigated through a static batch experiment under a set NaNO
3 ionic strength (0.01 mol·L
-1). Results show that, under the set NaNO
3 ionic strength, Cd
2+ adsorption of sepiolite and attapulgite of high grade and attapulgite of low grade is positively related to initial concentration of Cd
2+ in the solution, but negatively to solid-liquid ratio of the solution. Fitting with the Langmuir isothermal adsorption equation reveals an order of high grade attapulgite (33.67 mg·g
-1) >high grade sepiolite (25.55 mg·g
-1) >low grade attapulgite(11.52 mg·g
-1) >low grade sepiolite (5.24 mg·g
-1) in terms of theoretical saturated Cd
2+adsorption; Cd
2+ adsorption on sepiolite and attapulgite is strongly influenced by pH of the solution, and peaks when pH is 2-4; Cd
2+ adsorption on attapulgite is relatively stable and reaches equilibrium basically in 3 h; in solutions 0.01 mol·L
-1 NaNO
3 in ionic strength, 625 mg·L
-1 in initial Cd
2+ concentration, 15 g·L
-1 in clay mineral addition amount and 2-4 in pH, the minerals display an order of high grade sepiolite >high grade attapulgite >low grade attapulgite >low grade sepiolite in terms of Cd removal efficiency.