3D porous polymers for selective removal of CO2 and H2 storage: experimental and computational studies.

In this article, newly designed 3D porous polymers with tuned porosity were synthesized by the polycondensation of tetrakis (4-aminophenyl) methane with pyrrole to form M1 polymer and with phenazine to form M2 polymer. The polymerization reaction used p-formaldehyde as a linker and nitric acid as a catalyst. The newly designed 3D porous polymers showed permanent porosity with a BET surface area of 575 m2/g for M1 and 389 m2/g for M2. The structure and thermal stability were investigated by solid 13C-NMR spectroscopy, Fourier-transform infrared (FT-IR) spectroscopy, and thermogravimetric analysis (TGA). The performance of the synthesized polymers toward CO2 and H2 was evaluated, demonstrating adsorption capacities of 1.85 mmol/g and 2.10 mmol/g for CO2 by M1 and M2, respectively. The importance of the synthesized polymers lies in their selectivity for CO2 capture, with CO2/N2 selectivity of 43 and 51 for M1 and M2, respectively. M1 and M2 polymers showed their capability for hydrogen storage with a capacity of 66 cm3/g (0.6 wt%) and 87 cm3/g (0.8 wt%), respectively, at 1 bar and 77 K. Molecular dynamics (MD) simulations using the grand canonical Monte Carlo (GCMC) method revealed the presence of considerable microporosity on M2, making it highly selective to CO2. The exceptional removal capabilities, combined with the high thermal stability and microporosity, enable M2 to be a potential material for flue gas purification and hydrogen storage.

Selective Removal of Iron, Lead, and Copper Metal Ions from Industrial Wastewater by a Novel Cross-Linked Carbazole-Piperazine Copolymer.

A novel cross-linked Copolymer (MXM) was synthesized by the polycondensation reaction of 3,6-Diaminocarbazole and piperazine with p-formaldehyde as a cross-linker. The Copolymer was fully characterized by solid 13C-NMR and FT-IR. The thermal stability of MXM was investigated by TGA and showed that the Copolymer was stable up to 300 °C. The synthesized polyamine was tested for the removal of iron (Fe2+), lead (Pb2+), and copper (Cu2+) ions from aqueous and industrial wastewater solutions. The effect of pH, concentration and time on the adsorption of iron (Fe2+), lead (Pb2+), and copper (Cu2+) ions was investigated. The adsorption of the studied ions from aqueous solutions onto the MXM polymer occurs following the Freundlich isotherm and pseudo-second-order kinetic models. The intraparticle diffusion model showed that the adsorption mechanism is controlled by film diffusion. The regeneration of MXM showed practical reusability with a loss in capacity of 2-5% in the case of Fe2+ and Cu2+ ions. The molecular simulation investigations revealed similarities between experimental and theoretical calculations. Industrial wastewater treatment revealed the excellent capabilities and design of MXM to be a potential adsorbent for the removal of heavy metal ions.

Synthesis of a new thiophenol-thiophene polymer for the removal of mercury from wastewater and liquid hydrocarbons.

This work reports the synthesis of a novel thiophenol-thiophene polymer (termed KFUPM-Hg) and its suitability as an adsorbent for mercury removal from wastewater and liquid hydrocarbons. KFUPM-Hg was synthesized through a Friedel-Crafts polycondensation reaction of thiophenol and thiophene in the presence of p-formaldehyde as a linker. The crosslinked polymer structure was characterized using solid-state 13C-nuclear magnetic resonance (NMR) and Fourier-transform infrared spectroscopy (FTIR). Thermogravimetric analysis was performed to assess the polymer thermal stability, which indicated that the polymer is thermally stable to over 300 °C. A series of batch adsorption studies were used to investigate the effects of different parameters (pH, temperature, concentration, and time) on the mercury removal from aqueous solution as well as from a model liquid hydrocarbon media (decane/toluene mixture). The batch adsorption studies in aqueous media showed near quantitative removal of inorganic mercury (II) at 100 ppm using the thiophenol-thiophene polymer adsorbent. Furthermore, the thiophenol-thiophene polymer demonstrated excellent removal capabilities of methylmercury in a decane/toluene hydrocarbon mixture. Mercury adsorption onto KFUPM-Hg is an exothermic reversible physical process and follows pseudo-second order adsorption kinetics. Remarkably, these removal capabilities were achieved using polymers that directly incorporated thiophenol and thiophene groups during synthesis without the use of thiol-ene post-synthesis modifications.

Novel Porous Organic Polymer for the Concurrent and Selective Removal of Hydrogen Sulfide and Carbon Dioxide from Natural Gas Streams.

Natural gas sweetening currently requires multistep, complex separation processes to remove the acid gas contaminants, carbon dioxide and hydrogen sulfide. In addition to being widely recognized as energy inefficient and cost-intensive, the effectiveness of this conventional process also suffers considerably because of limitations of the sorbent materials it employs. Herein, we report a new porous organic polymer, termed KFUPM-5, that is demonstrated to be effective in the concurrent separation of both hydrogen sulfide and carbon dioxide from a mixed gas stream at ambient conditions. To understand the ability of KFUPM-5 to selectively capture these gas molecules, we performed both pure-component thermodynamic and mixed gas kinetic adsorption studies and correlated these results with theoretical molecular simulations. Our results show that the underlying polar backbone of KFUPM-5 provides favorable adsorption sites for the selective capture of these gas molecules. The outcome of this work lends credence to the prospect that, for the first time, porous organic polymers can serve as sorbents for industrial natural gas sweetening processes.

Novel cross-linked melamine based polyamine/CNT composites for lead ions removal.

A novel series of polyamine/CNT composites were synthesized via a single step polycondensation reaction of melamine, paraformaldehyde, various alkyldiamines and chlorinated carbon nanotubes (CNT) at optimized reaction conditions in the presence of N, N-Dimethyl formamide as a solvent. Chlorinated carbon nanotubes synthesized by reacting acidified CNT and thionyl chloride was used. The pure polymer (MFDH) and the functionalized composites (MFDH1, MFDH2, MFDH3 and MFDH4) having 0.01, 0.02, 0.05 and 0.1% weight of the starting precursors were used. The morphology, surface area, molecular structures and overall properties of the new series of polymers were characterized using Raman Spectroscopy, FT-IR, 13C NMR, X-ray diffraction experiments, BET and TGA. A comprehensive design was set up in order to evaluate the effects of pH, temperature, Lead ion initial concentrations and contact time on the ability of the new series of functionalized polymers for Lead (II) ion removal. Wastewater treatment revealed the high efficacy of the synthesized polyamine/CNT composite in the removal of ∼99% of Lead ions in wastewater samples.

Novel cross-linked polymers having pH-responsive amino acid residues for the removal of Cu2+ from aqueous solution at low concentrations.

Two novel cross-linked anionic polyelectrolytes (CAPE) I and II containing pH-responsive amino acid residues have been synthesized via cycloco- and ter-polymerization of a monomer having diallylammonioethanoate motif (90mol%) and a cross-linker 1,1,4,4-tetraallylpiperazinium dichloride (10mol%) in the absence and presence of SO2 (100mol%), respectively. The experimental data for the adsorption of Cu(2+) on the CAPES fitted Lagergren second-order kinetic model thereby indicating the chemical nature of the adsorption process. The fitness order of Freundlich>Langmuir>Temkin for the isotherm models for CAPE I showed the favorability of adsorption on a heterogeneous surface, whereas for CAPE II the fitness order of Langmuir>Freundlich>Temkin certified the favorability toward monolayer adsorption. The adsorption process was spontaneous and endothermic in nature with negative and positive values for ΔG and ΔH, respectively. For the sorbents CAPE I and CAPE II, the efficiency of Cu(2+) removal at an initial metal concentration of 200ppb was found to be 77.5 and 99.4%, respectively. Desorption efficiencies were found to be 88 and 93% for CAPE I and CAPE II, respectively. Treatment of real wastewater samples spiked with Cu(2+) ions showed the excellent ability of the resins to adsorb metal ions.