Adsorption of cadmium from aqueous solutions using Moringa oleifera kraft pulp microfibers functionalized with iron oxide nanoparticles

Abstract This study evaluated microfibrillated adsorbents obtained from kraft pulp (PC) cellulose of Moringa oleifera (M. oleifera). In this research, Cd (II) adsorption was evaluated on unmodified microfibrillated cellulose (PMC) and hematite-modified microfibers (SN-PMC) on kraft pulp as starting material cooked for 10 min. This cellulose pulp as a starting material was also used in a previous work from our research group but with a 20-min pulping cooking to obtain a composite of nanofibers and maghematite, obtaining less favorable results in terms of cadmium adsorption capacity, with a qt = 12 mg/g. PMC and SN-PMC were characterized by SEM–EDS, XRD, zeta potential and FTIR. The experimental kinetic and equilibrium results on PMC and SN-PMC were modeled, obtaining a pseudo-first-order kinetic fit result on SN-PMC and an Elovich approach on the PMC adsorbent. Regarding the equilibrium in both materials, the adsorption isotherms were fitted to the Langmuir model. The maximum adsorption capacities (Qo) were 27.3 mg/g and 33.8 mg/g for PMC and SN-PMC, respectively, obtained from isothermal data at 25 °C and pH 5, which were the conditions with the highest adsorption in isotherms. The main adsorption mechanism is chemisorption; however, it was concluded that SN-PMC was dominated by physisorption and chemisorption, which gives rise to a hybrid mechanism. On the other hand, both adsorbents presented spontaneous and exothermic process. These materials, especially SN-PMC, have potential in the removal of cadmium from industrial effluents. Their low cost, biocompatibility, and efficiency can contribute to the development of sustainable adsorbents, with the role of iron oxide highlighted in the removal. Future research could evaluate the material to improve its adsorption capacity in multicomponent mixtures or evaluate its regeneration and reuse. Graphical Abstract