Low-cost adsorbent from biomass for removal of Fe(II) and Mn(II) for water treatment: batch and column adsorption study

The current investigation aimed on  harnessed agricultural waste derived from Aloe vera as an efficient adsorbent to adsorb heavy metals such as Mn(II) and Fe(II) ions from water. The Acid Modified Aloe vera adsorbent (AMA), underwent a thorough characterization process such as point of zero charges, Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) analysis depicted an uneven and highly porous surface, and BET analysis, respectively. The utilization of the low-cost AMA adsorbent yielded noteworthy outcomes, showcasing a remarkable adsorption capacity. Specifically, the adsorbent exhibited a maximum adsorption capacity of 45.120 mg/g for Mn(II) ions and 41.282 mg/g for Fe(II) ions. These results were observed under conditions of 298 K temperature, a pH of 7, an AMA dose of 0.1 g/L, 100 mg/L initial concentration, and contact duration of 130 min. Various kinetic models were explored, including the pseudo-first-order (PFO), pseudo-second-order (PSO), Elovich, and intra-particle diffusion models. Among these, the PFO model exhibited the best association with the experimental data, with a high R² value of 0.997. Similarly, Langmuir and Freundlich isotherm analyses were conducted. From the observed experimental, it was found that the Langmuir isotherm displayed superior fitting with an R² value of 0.997. Considering these outcomes, the AMA adsorbent emerges as a viable candidate for treating water contaminated predominantly with Fe(II) and Mn(II) ions.