Abstract
This work informs on the green synthesis of a novel adsorbent and its adsorption capacity. The adsorbent was synthesized by the combination of iron nanoparticles and cellulose nanofibers (FeNPs/NFCs). Cellulose nanofibers (NFCs) were obtained from Moringa (Moringa oleifera Lam.) by a pulping Kraft process, acid hydrolysis, and ultrasonic methods. The adsorption method has advantages such as high heavy metal removal in water treatment. Therefore, cadmium (Cd) and lead (Pb) adsorption with FeNP/NFC from aqueous solutions in batch systems was investigated. The kinetic, isotherm, and thermodynamic parameters, as well as the adsorption capacities of FeNP/NFC in each system at different temperatures, were evaluated. The adsorption kinetic data were fitted to mathematical models, so the pseudo-second-order kinetic model described both Cd and Pb. The kinetic rate constant (K2), was higher for Cd than for Pb, indicating that the metal adsorption was very fast. The adsorption isotherm data were best described by the Langmuir–Freundlich model for Pb multilayer adsorption. The Langmuir model described Cd monolayer sorption. However, experimental maximum adsorption capacities (qe exp) for Cd (>12 mg/g) were lower than those for Pb (>80 mg/g). In conclusion, iron nanoparticles on the FeNP/NFC composite improved Cd and Pb selectivity during adsorption processes, indicating the process’ spontaneous and exothermic nature.
Highlights
Water pollution by heavy metals is one of the most severe environmental problems, with industrial processes being their main anthropogenic sources
Where qt is the amount of ion adsorbed, at a time (t), per weight of adsorbent, qe is the concentration of solute removed at the equilibrium per weight of adsorbent, KL is the pseudo-first-order kinetic constant (1/min), K2 is the pseudo-second-order rate constant of sorption (g/mg.min), and a and b are the Elovich constants related to the initial adsorption rate and desorption rate (g/mg), respectively
The results indicate a certain percentage of Fe adhered to the surface, which is related to the synthesis of NPs
Summary
Water pollution by heavy metals is one of the most severe environmental problems, with industrial processes being their main anthropogenic sources. Seeds, stem, and leaf extracts from different plants contain useful polyphenols for metal reduction These substances have been researched as bioreducing agents to synthesize nanoparticles, such as Vitex negundo L., E. condylocarpa, and Amaranthus dubius [32,33,34,35]; including Rumex acetosa [36], Eucalyptus globulus [37], Mukia maderaspatana [38], Camellia sinensis [39], Rosemarinus officinalis [40], Citrus maxima [41], Azadirachta Indica [30,42], green tea [43], eucalyptus [44], and Canna indica [21]. The influence of contact time, temperature, and pH on adsorption experiments was determined, as were the adsorption mechanisms and thermodynamic, kinetic, and isothermal parameters of the studied systems
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