Impact of environmental conditions on the removal of Ni(II) from aqueous solution to bentonite/iron oxide magnetic composites

Selective removal of some heavy metals from Lanthanide solution by graphene oxide functionalized with sodium citrate

Lanthanides are widely used in several advanced technologies, and the presence of heavy metal ions as traces reduce their efficiencies. Hence, adsorption of some heavy metals from Lanthanides aqueous solution using previously prepared graphene oxide-citrate (GO-C) composite was reported. In this regard, the GO-C was applied to remove various heavy metal ions (Fe, Ni, Mn) through the batch technique. The GO-C after the adsorption process was characterized by various advanced techniques. The results obtained from the experimental investigations revealed that the GO-C showed a rapid equilibrium adsorption time (1.0 min) for all the studied heavy metal ions. Moreover, the adsorption isotherm data for Fe3+, Mn2+, and Ni2+ was fit by the Langmuir isotherm model with excellent adsorption capacity for Fe3+ (535.0 mg/g), Mn2+ (223.22 mg/g), and Ni2+ (174.65 mg/g). Furthermore, the GO-C can be reused over five times to enhance the removal efficiency. Interestingly, the GO-C adsorbent achieved removal performance reached 95.0% for the Fe3+ and ≥ 35.0% for Ni, Mn, Co, and Cu compared to < 1% for lanthanides metal ions.

Removal of Pb(II) from aqueous solutions by adsorption on magnetic bentonite

Bentonite is a porous clay material that shows good performance for adsorbing heavy metals and other pollutants for wastewater remediation. In our previous study, magnetic bentonite (M-B) was prepared to solve the separation problem and improve the operability. In this study, we investigated the influence of various parameters on the Pb(II) adsorption of M-B, and it showed effective performance. About 98.9% adsorption removal rate was achieved within 90 min at adsorbent dose of 10 g/L for initial Pb(II) concentration of 200 mg/L at 40 °C and pH 5. The adsorption kinetic fit well by the pseudo-second-order model, and also followed the intra-particle diffusion model up to 90 min. Moreover, adsorption data were successfully reproduced by the Langmuir isotherm; the maximum adsorption capacity was calculated as 80.40 mg/g. The mechanism of interaction between Pb(II) ions and M-B was ionic exchange, surface complexation, and electro-static interactions. Thermodynamics study indicated that the reaction of Pb(II) adsorption on M-B was endothermic and spontaneous; increasing the temperature promoted adsorption. This study was expected to provide a reference and theoretical basis for the treatment of Pb-containing wastewater using bentonite materials.