Activated Carbon from Yam Peels Modified with Fe3O4 for Removal of 2,4-Dichlorophenoxyacetic Acid in Aqueous Solution

Abstract

The removal of organic pollutants from water sources can be enhanced using suitable adsorbents. The aim of this research was to study the adsorption capacity and potential reuse of a magnetic adsorbent prepared from agricultural wastes of yam peels (Dioscorea rotundata) for 2,4-dichlorophenoxyacetic (2,4-D) acid removal. The procedure was performed through carbonization and activation at 400 and 500 °C, respectively. Then, the as-prepared activated carbon (AC) was chemically modified using magnetite (Fe3O4) nanoparticles. The AC and magnetic activated carbon (MAC) were characterized and then used for batch adsorption and regeneration tests at different pH, initial concentrations of 2,4-D, and temperature. AC and MAC were showed to have microporous structures with surface areas of 715 and 325 m2/g, respectively. Superparamagnetic behavior was observed for MAC with a saturation magnetization of 6 emu/g. The results from the batch experiments showed higher adsorption capacity at high initial concentration of 2,4-D, low pH, and room temperature. The thermodynamic parameters indicated that the experiments proceeded as exothermic and spontaneous adsorption. Our findings also showed that MAC can be separated from the water medium through a facile magnetic procedure, and from regeneration experiments, MAC showed better results with 60% of its initial adsorption capacity after five cycles. Hence, MAC was found to be a promising alternative adsorbent of pesticides in water.

Ionic Cross-Linking Fabrication of Chitosan-Based Beads Modified with FeO and TiO2 Nanoparticles: Adsorption Mechanism toward Naphthalene Removal in Seawater from Cartagena Bay Area

“…Moreover, n values above 1.0 indicate that the adsorption process was carried out mainly by chemisorption and electrostatic interaction, rather than physical adsorption. 65 Additionally, K f constant is considerably high at 25 °C, which is generally typical for adsorption processes with endothermic nature. 66 Moreover, lower q m values are related to the high amount of water in the un-Ch, affecting the maximum quantity of naphthalene adsorbed in the available active sites.…”

“…Here, the Ch-FeO/TiO 2 presented higher q m values compared to the un-Ch (see Table 3 ), and the K L constant values indicated good adsorption performance. 65 However, the lower K L for un-Ch was attributed to the bonding interaction between the functional groups within the chitosan structure during the ionic cross-linking procedure, which reduces the available active sites, and thus, the q m value (70.9 mg/g). Meanwhile, the presence of nanoparticles in the Ch-FeO/TiO 2 allowed improving the q m value to 149.3 mg/g due to the conferring of a larger surface area for more available active sites in the chitosan for adsorption of naphthalene.…”

“…The experimental data were adjusted using four different kinetics models, considering the pseudo-first-order model ( eq 3 ), pseudo-second-order model ( eq 4 ), Elovich model ( eq 5 ), and Weber–Morris model ( eq 6 ). 65 where q t is the naphthalene adsorbed at the given time (mg/g), q e is the naphthalene adsorbed at the equilibrium (mg/g), k 1 is the pseudo-first-order constant, t is the given time (min), k 2 is the pseudo-second-order constant, α and β are the Elovich adsorption and desorption rate, respectively, C is the boundary layer effect (mg/g), and k p is the intraparticle diffusion constant.…”

Synthesis of FeO@SiO2–DNA core–shell engineered nanostructures for rapid adsorption of heavy metals in aqueous solutions

“…The Elovich model also predicts chemisorption as the adsorption mechanism, in which an exponential increase of the adsorption is promoted by the availability and heterogenicity of the active sites. 40 Here, the different activation energies of the heterogeneous sites follow second-order reactions, suggesting a direct relation with the pseudo-second order model. 70 The rapid and exponential adsorption rate was corroborated with the high a values, and were in agreement with the pseudo-second order constant.…”

“…The kinetic models considered were pseudo-rst order, pseudo-second order, Elovich, and intraparticle diffusion, which are accordingly expressed in eqn (4)-(7). 40 logðq t À q e Þ ¼ log q e À k 1 t 2:303 (4)…”