Removal of Cu2+ and Cd2+ from Aqueous Solution by Bentonite Clay Modified with Binary Mixture of Goethite and Humic Acid

Abstract

Pre-modification of bentonite clay with goethite, humic acid, and a binary mixture of goethite and humic acid reagents increased its cation exchange capacity from 95 to 105.32, 120.4, and 125.8 meq/ 100 g of bentonite clay, respectively. The effective pre-modification of bentonite clay with goethite, humic acid, and goethite-humic acid reagents was confirmed from their Fourier transform infrared spectra which suggested that modification was effective on the AlAlOH and Si-O sites for goethite and humic acid modification and AlAlOH for goethitehumic acid modification. The presence of 0.001 M NaNO 3 electrolyte increased the adsorption capacity of bentonite clay. Temperature was observed to favor the adsorption of Cu 2+ and Cd 2+ onto both the raw and modified bentonite clay samples. The goethitehumic acid-modified bentonite gave the best adsorption capacity of ≈10 and 16 mg/g at 30 and 50°C, respectively, for both metal ions. The inner sphere complexation mechanism was suggested for the adsorption of both metal ions onto the modified adsorbents. Modifying bentonite clay with a binary mixture of goethite and humic acid reduced the selectivity of bentonite clay for either Cu 2+ or Cd 2+ . Preadsorbed goethite and humic acid on bentonite clay will further reduce the mobility of heavy metal ions in soils and in aquatic environments.

Competitive adsorption of metal ions onto goethite–humic acid-modified kaolinite clay

“…It is observed that with the adsorption of metal ions, the peaks at around 3440 and 1030 cm -1 became broad even though there were no significant shifts in these peaks. This indicates an interaction between the metal ions and the modified material (Olu-Owolabi et al 2010). With modification of the kaolinite clay with a binary of goethite and humic acid, cation exchange capacity of the clay increase from 7.81 meq/100 g to 40 meq/100 g while the specific surface area (13 m 2 /g) was the same as that reported by Adebowale et al (2006).…”

“…After aging, the sample was dried at 50°C, pulverized and sieved through 20-lm sieve. Five percent goethitehumic acid mixture was used for modification based on our previous study (Olu-Owolabi et al 2010). The modified kaolinite produced is now referred to as GHA-modified kaolinite clay adsorbent.…”

“…Although we have initially reported the use of a binary mixture of geothite and humic acid for the modification of bentonite (Olu-Owolabi et al 2010), yet no detailed report exists on the impact of some operational variables on the efficiency of a pre-adsorbed humic acid ? goethite-modified clay in immobilizing heavy metal ions from aqueous systems.…”

Effects of Bentonite Activation Methods on Chitosan Loading Capacity

“…The loading of chitosan on bentonite was examined using various reaction times (10-90 min), initial chitosan concentrations (250-2500 mg/L), stirring speeds (50-300 rpm), temperatures (30-50 °C), and pH values (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12). Specifically, 1 g of raw bentonite clay was dispersed in 150 mL of distilled water.…”

“…Meanwhile, bentonite clay remediates some disadvantages of chitosan that affect its adsorption efficacy, e.g. low density, the tendency to float, and difficulty in making contact with pollutants [7,8]. On the other hand, various modification techniques, including acid and thermal (by calcination or microwave radiation) treatments, have been reported to affect the adsorption properties of nature clays for metal ions in aqueous solutions [9][10][11].…”