Synthesis of porous polyurea monoliths assisted by centrifugation as adsorbents for water purification

Solvothermal Preparation of Microporous Polyureas for Au(III) Adsorption

The enrichment and recovery of gold from wastewater are an alternative method to obtain this noble metal, which benefits reducing hazardous emissions from the conventional ore mining process and reserving natural gold for sustainable development. Inspired by our previous work (Lei et al., Macromol. Rapid Comm. 2022, 2200712), four families of microporous polyureas (mPPUs) with a large surface area (690 m2 g-1) and abundant heteroatom sites have been prepared via the factor-optimized solvothermal protocol. The resultant sample NPU-A starting from 1,5-naphthalene diisocyanate (NDI) and tri(4-aminophenyl) amine (TAPA) exhibits the maximum Au(III) adsorption capacity of 1300 mg g-1 and high selectivity even when the Au(III) concentration is as low as 0.1 mg L-1. This study not only demonstrates the robustness of the high-throughput synthetic strategy but also promotes the investigation of the structure-activity correlation between the mPPU chemical structure and Au(III) adsorption performance.

Porous polyvinyl alcohol/graphene oxide composite film for strain sensing and energy-storage applications

In this study, a flexible porous polyvinyl alcohol (PVA)/graphene oxide (GO) composite film was developed and tested for flexible strain sensing and energy-storage applications. Morphology and mechanical properties were studied; tensile strength and Young's modulus increased by 225% and 86.88%, respectively, at 0.5 wt% GO. The PVA/GO film possesses exceptional sensing ability to various mechanical strains, such as tension, compression, bending, and torsion. For example, the gauge factor of the PVA/GO film as a tensile-strain sensor was measured as 2.46 (246%). Under compression loads, the PVA/GO composite film showed piezoresistive and capacitive strain-sensing characteristics. Under 5 kPa of compression load, the relative resistance increased by 81% with a 100 msec response time; the relative capacitance increased by 160% with a 120 msec response time. The PVA/GO strain sensor exhibited high durability and reliability over 20 × 10³cycles of tensile strain and bending at 3.33 Hz. Moreover, the PVA/GO composite film showed good electrochemical properties due to its porous structure; the maximum capacitance was 124.7 F g^-1at 0.5 wt% GO. After 20 × 10³charging-discharging cycles, the capacitance retention rate was 94.45%, representing high stable capacitance performance. The results show that electrically conductive porous PVA nanocomposite films are promising candidates for strain sensing and energy-storage devices.

Polyureas Versatile Polymers for New Academic and Technological Applications

Polyureas (PURs) are a competitive polymer to their analogs, polyurethanes (PUs). Whereas PUs' main functional group is carbamate (urethane), PURs contain urea. In this revision, a comprehensive overview of PUR properties, from synthesis to technical applications, is displayed. Preparative routes that can be used to obtain PURs using diisocianates or harmless reagents such as CO₂ and NH₃ are explained, and aterials, urea monomers and PURs are discussed; PUR copolymers are included in this discussion as well. Bulk to soft components of PUR, as well as porous materials and meso, micro or nanomaterials are evaluated. Topics of this paper include the general properties of aliphatic and aromatic PUR, followed by practical synthetic pathways, catalyst uses, aggregation, sol-gel formation and mechanical aspects.

Preparation of Polystyrene Microsphere-Templated Porous Monolith for Wastewater Filtration

Porous monoliths prepared using templates are highly sought after for filtration applications due to their good mass transport properties and high permeability. Current templates, however, often lead to the formation of dead-end pores and irregular pore distributions, which reduce the efficiency of the substrate flow across the monolith column. This study focused on the preparation of a microsphere-templated porous monolith for wastewater filtration. The optimal template/monomer ratio (50:50, 60:40, 70:30) was determined, and appropriate template removal techniques were assessed for the formation of homogenous pores. The physicochemical characteristics and pore homogeneity of the monoliths were examined. The 60:40 ratio was determined to result in monoliths with homogeneous pore distributions ranging from 1.9 μm to 2.3 μm. SEM and FTIR investigations revealed that solvent treatment was effective for removing templates from the resulting solid monolith. The water quality assessments revealed reductions in the turbidity and the total number of suspended particles in the tested wastewater of up to 96–99%. The findings of this study provide insightful knowledge regarding the fabrication of monoliths with homogenous pores that are beneficial for wastewater treatment.

Evaluation of Polyurea-Crosslinked Alginate Aerogels for Seawater Decontamination

Polyurea-crosslinked Ca-alginate (X-Ca-alginate) aerogel beads (diameter: 3.3 mm) were evaluated as adsorbents of metal ions, organic solvents, and oils. They were prepared via reaction of an aromatic triisocyanate (Desmodur RE) with pre-formed Ca-alginate wet gels and consisted of 54% polyurea and 2% calcium. X-Ca-alginate aerogels are hydrophobic nanoporous materials (90% v/v porosity), with a high BET surface area (459 m²/g⁻¹), and adsorb Pb^II not only from ultrapure water (29 mg/g⁻¹) but also from seawater (13 mg/g⁻¹) with high selectivity. The adsorption mechanism involves replacement of Ca^II by Pb^II ions coordinated to the carboxylate groups of the alginate backbone. After treatment with a Na₂EDTA solution, the beads can be reused, without significant loss of activity for at least two times. X-Ca-alginate aerogels can also uptake organic solvents and oil from seawater; the volume of the adsorbate can be as high as the total pore volume of the aerogel (6.0 mL/g⁻¹), and the absorption is complete within seconds. X-Ca alginate aerogels are suitable for the decontamination of aquatic environments from a broader range of inorganic and organic pollutants.