Adsorption Thermodynamics and Kinetics of Resin for Metal Impurities in Bis(2-hydroxyethyl) Terephthalate

Sustainable utilization of chemically depolymerized polyethylene terephthalate (PET) waste to enhance sand-bentonite clay liners

Polyethene terephthalate (PET) waste poses major environmental harm which can be minimized by reusing it in clay soil stabilization. In general, various polymers are known to reduce hydraulic conductivity and increase the shear strength of clays. However, the application of the effect of a chemically depolymerized form of PET, i.e., Bis (2-Hydroxyethyl) terephthalate (BHET) has not been performed as an additive in Compacted Clay Liners (CCLs) for landfills. This research focuses on the effect of the air curing period (1 and 28 days) on the hydromechanical behavior of BHET-treated SBM (0, 1, 2, 3, and 4 % by dry weight). Results from One Dimensional Consolidation tests showed that an increase in BHET content reduced both compressibility and hydraulic conductivity of SBM due to pore clogging mechanism of swollen BHET hydrogel, however, hydraulic conductivity reduced over 28 days of curing due to loss in re-swelling availability of the hydrogel, thereby allowing less tortuous paths to flow. Results from Consolidated-Drained Direct Shear tests showed that for 1 and 28-days curing, BHET treatment to SBM increased the cohesion (c') due to strong polymer interparticle bridging, however, polymer coating over the sand grains causes a reduction in its surface roughness to decrease the frictional angle (ϕ'). SEM (Scanning Electron Microscopy) and EDX (Energy-dispersive X-ray spectroscopy) analysis on BHET-treated specimens support the flocculation of bentonite, polymer bridging of sand and clay-sand polymer links. A significant Pb²⁺ removal capacity was also observed with BHET-treated SBM from the batch tests. FTIR (Fourier Transform Infrared Spectroscopy) analysis on batch sorption specimens confirms the role of the carbonyl groups (C = O) and hydroxyl groups (OH) present in the BHET structure indicating the possibility to adsorb Pb²⁺. The findings of the study suggested that a mechanism of interaction exists between sand-bentonite and BHET polymer and it can be adopted in CCLs design.

Novel Polymer Sorbents with Imprinted Task-Specific Ionic Liquids for Metal Removal

In this paper, the potential of novel polymer sorbents with the imprinted IL-functional group for the removal of Cu(II), Cd(II), and Zn(II) from aqueous solutions was investigated by batch mode. The sorbents were fabricated by direct reaction of the prepared polymer matrix (poly(vinylbenzyl chloride-divinylbenzene), VBC, and poly(vinylbenzyl bromide-divinylbenzene), VBBr) with 1-(3- or 4-pyridyl)undecan-1-one and oxime of 1-(3- or 4-pyridyl)undecan-1-one. The Fourier Transform Infrared Spectroscopy (FT-IR), Raman Spectroscopy (Raman), Thermogravimetric Analysis (TG), Differential Scanning Calorimetry (DSC), and Scanning Electron Microscopy (SEM) techniques were used to show functionality and stability of the sorbents. The materials were also characterized by contact-angle goniometry, X-rayphotoelectron spectroscopy (XPS), and Zeta potential analysis. The removal of Cd(II), Cu(II), and Zn(II) was monitored and optimized under the influence of several operational controlling conditions and factors such as pH, shaking time, temperature, initial metal ions concentration, and counter-ions at the functional group. The results obtained confirmed the very high potential of the sorbents; however, the properties depend on the structure of the functional group. The tested sorbents showed fast kinetics, significant capacity at 25 °C (84 mg/g for the Zn(II) sorption with VBC-Ox4.10, 63 mg/g for the Cd(II) sorption with VBBr-Ox3.10, and 69 mg/g for the Cu(II) sorption with VBC-K3.10), and temperature dependence (even 100% increase in capacity values at 45 °C). The selected sorbent can be regenerated without a significant decrease in the metal removal efficiency.