Adsorption Characteristics of Leonardite for Removal of Cd(II) and Zn(II) from Aqueous Solutions

Abstract

Leonardite was used as an adsorbent for the removal of Cd(II) and Zn(II) from aqueous solutions. The characteristics of leonardite were determined using XRD, XRF, FTIR, and SEM. Adsorption of Cd(II) and Zn(II) on leonardite, in batch system at 30 °C, was investigated to achieve the optimum condition for metals removal. Studies were carried out at different pH, contact time, and initial metal concentration. It was found that adsorption of metals ions was strongly influenced by pH value. The optimum adsorption conditions obtained were pH 6 and contact time of 60 min. Adsorption data were interpreted to kinetic models, including pseudo-first-order, pseudo-second-order, intra-particle diffusion, and adsorption isotherm models, including Langmuir isotherm and Freundlich isotherm. Pseudo-second-order kinetic model was suitable for describing adsorption of Cd(II) and Zn(II) on leonardite. Both Langmuir and Freundlich isotherms fitted well with the adsorption data of Zn(II) whereas the adsorption of Cd(II) better fitted to Freundlich isotherm.

Adsorptive capacity and kinetic studies of PK216 resin for the extraction of Pr, Gd, and Dy rare earth elements

“…The same applies to Gd and Dy as both fit better to Langmuir than Freundlich, assuming the binding of PK216 resin sites is equal in terms of its affinity for the adsorbate. For Gd, the result is in agreement with the literature, where the adsorption energy of PK216 is equivalent to the surface site for Gd 54,55 . In the final stage, the PK216 resin adsorbent reaches equilibrium as the surface becomes saturated with a monolayer of Pr, Gd, and Dy molecules, respectively 37 …”

“…The REE ions must go through external diffusion phases such as liquid film and intraparticle diffusion before reaching the adsorbent surface sites for ion exchange to occur. In general, the adsorption of Pr, Gd, and Dy on PK216 resin is not entirely controlled by intraparticle diffusion; instead, the film diffusion and intraparticle diffusion both influence the diffusion of Pr, Gd, and Dy, thus contributing to the adsorption resistance rate 54,62,63 …”

“…For Gd, the result is in agreement with the literature, where the adsorption energy of PK216 is equivalent to the surface site for Gd. 54,55 In the final stage, the PK216 resin adsorbent reaches equilibrium as the surface becomes saturated with a monolayer of Pr, Gd, and Dy molecules, respectively. 37 Kinetic model analysis Thermodynamic data predict the final state of adsorption based on the initial non-equilibrium mode.…”

“…In general, the adsorption of Pr, Gd, and Dy on PK216 resin is not entirely controlled by intraparticle diffusion; instead, the film diffusion and intraparticle diffusion both influence the diffusion of Pr, Gd, and Dy, thus contributing to the adsorption resistance rate. 54,62,63 Based on the models discussed, the diffusion mechanisms of Pr, Gd, and Dy before reaching the PK216 surface sites can be outlined as follows:…”

Effect of a Natural Adsorbent Mixture (Zeolite and Leonardite) on the Reduction of Ammonia Caused by Fish Feed

“…At the end of the experiment, in which the use of leonardite (another natural adsorbent) together with zeolite has a positive influence on ammonia removal, agrees with the studies of Öz et al (2016) and Şahin et al (2019). Chammui et al (2014) and Terdputtakun et al (2017) demonstrated that leonardite is more beneficial in removing unwanted compounds in aquatic environments. Furthermore, similar to this study, it was reported by Zengin (2013) and Şahin (2022) that the use of a clinoptilolite-leonardite mixture was effective.…”