Adsorption of Cadmium Ions from an Aqueous Solution on a Highly Stable Dopamine-Modified Magnetic Nano-Adsorbent

Abstract

Magnetic nanomaterials were functionalized with dopamine hydrochloride as the functional reagent to afford a core–shell-type Fe3O4 modified with polydopamine (Fe3O4@PDA) composite, which was used for the adsorption of cadmium ions from an aqueous solution. In addition, the effects of environmental factors on the adsorption capacity were investigated. Furthermore, the adsorption kinetics, isotherm, and thermodynamics of the adsorbents were discussed. Results revealed that the adsorption of cadmium by Fe3O4@PDA reaches equilibrium within 120 min, and kinetic fitting data are consistent with the pseudo-second-order kinetics (R2 > 0.999). The adsorption isotherm of Cd2+ on Fe3O4@PDA was in agreement with the Freundlich model, with the maximum adsorption capacity of 21.58 mg/g. The thermodynamic parameters revealed that adsorption is inherently endothermic and spontaneous. Results obtained from the adsorption–desorption cycles revealed that Fe3O4@PDA exhibits ultra-high adsorption stability and reusability. Furthermore, the adsorbents were easily separated from water under an enhanced external magnetic field after adsorption due to the introduction of an iron-based core. Hence, this study demonstrates a promising magnetic nano-adsorbent for the effective removal of cadmium from cadmium-containing wastewater.Graphical Abstract

Magnetically Functionalized Moss Biomass as Biosorbent for Efficient Co2+ Ions and Thioflavin T Removal

“…Similar results were reported for Pb 2+ and Cd 2+ biosorption by magnetic Bauhinuia purpurea pods [ 10 ]. Lei et al [ 25 ] revealed that Fe 3 O 4 magnetic nanoparticles exhibited a more rapid adsorption rate in the initial phase of Cd 2+ adsorption (before 90 min) and then, similarly as in our experiments, the adsorption rate tends to be flat. The observed distinctions in the kinetics profiles of organic dye and metal ions are caused by (1) different mechanisms of Co 2+ and TT adsorption, and (2) the distinct affinity of Co 2+ and thioflavin T to binding sites on magnetically responsive biosorbent.…”

Adsorption of lead ions from wastewater using nano silica spheres synthesized on calcium carbonate templates

“…In addition, a high initial metal ion concentration enhances diffusion from the solution to the adsorbent's active sites i.e. there is an increase in the diffusion gradient leading to an increase in the mass transfer process (Lei et al, 2019). In general, our experimental results elucidate that there is a positive correlation between the initial metal ion concentration and adsorption capacity.…”

“…They attributed this observation to a decrease in binding sites with an increase in initial metal ion concentration due to saturation of the binding sites. El-Naggar et al (2019) observed a similar trend when they employed a Kaolinite/Smectite natural composite adsorbent to study the removal of Pb 2þ ions from wastewater, using different concentrations of Pb 2þ ions ranging from 125 to 500 mg/L Lei et al (2019) also observed a similar trend when using dopamine-modified magnetic nano-adsorbents to adsorb Cd 2þ ions from an aqueous solution.…”

“…For Pb 2þ ions to be adsorbed, dehydration has to occur, and the process has to absorb heat that is availed by an increase in temperature (Lei et al, 2019). As the temperature further increases, the degree of hydration of hydrated metal ions also increases, justifying improved adsorption rates associated with higher temperatures (Lei et al, 2019). Mustapha et al (2019) argued that the increase in adsorption capacity with an increase in temperature resulted in an increase in the mobility of the Pb 2þ metal ions as they acquired more kinetic energy due to increased velocity resulting from higher temperatures in the system.…”

Preparation of terpyridine-functionalized paramagnetic nickel–zinc ferrite microspheres for adsorbing Pb(ii), Hg(ii), and Cd(ii) from water

“…Researchers oen modify the surface of materials to improve their acid/base resistance, adsorption, and selectivity. [31][32][33] The adsorption interaction between metal ions and functional groups mainly include ionic bonds and covalent bonds. 34 To enhance the adsorption capacity of ions, we designed a magnetic adsorbent with terpyridyl groups.…”