Emulsion-templated macroporous ammonium based polymers: Synthesis and dye adsorption study

High Internal Phase Emulsion for Constructing Chiral Helical Polymer-Based Circularly Polarized Luminescent Porous Materials

Polymerized high internal phase emulsions (polyHIPEs) with circularly polarized luminescence (CPL), as an interesting class of porous materials, are of great significance for the development of CPL porous materials but have not been reported so far. Herein, we report the construction of polyHIPE-based CPL porous materials, taking advantage of an adsorption strategy. The pristine polyHIPEs constructed by chiral helical polymers, which acted as a chiral microenvironment, were fabricated by coordination polymerization of chiral acetylene monomers (R/S-SA) using HIPEs as templates. Achiral fluorescent small molecules were dispersed in the pores of the 3D porous organic chiral polymer matrix provided by polyHIPEs through the adsorption strategy, and CPL-active porous materials with blue, cyan, and green emissions were constructed using a fluorescence-selective absorption mechanism that does not rely on chirality transfer at the molecular level. The maximum luminescence dissymmetry factor (glum) value was -2.6 × 10-2. This work establishes a new and simple way for developing CPL porous materials.

Fabrication of porous adsorbents from eco-friendly aqueous foam for high-efficient removal of cationic dyes and sustainable utilization assessment

Porous materials applied in environmental remediation have received researchers' extensive attention recently, but the related green and convenient preparation method is rarely reported. Here, we recommended a green and convenient strategy for the fabrication of porous material via aqueous foam templates, which was synergistically stabilized by Codonopsis pilosula (CP) and clay minerals of attapulgite (APT). The characterization results revealed that the APT was modified by organic molecules leached from CP and anchored at the air-water interface, which improved the foam stability significantly. The novel porous material of polyacrylamide/Codonopsis pilosula/attapulgite (PAM/CP/APT) templated from the aqueous foam via a polymerization reaction had excellent adsorption capacity for the cationic dyes methyl violet (MV) and methylene blue (MB), and the adsorption capacity can reach 755.85 mg/g and 557.64 mg/g, respectively. More importantly, the adsorption capacity of spent adsorbent material was still over 200 mg/g after being recycled five times through a simple carbonization process, and then it was added to the plant pot, the total biomass was increased by about 86.42%. This study provided a green and sustainable pathway for the preparation, application and subsequent processing of porous materials.

Alginate-based porous polyHIPE for removal of single and multi-dye mixtures: Competitive isotherm and molecular docking studies

A novel hydrophilic porous alginate-based polyHIPE (AGA) was synthesized via an oil-in-water emulsion templating approach. AGA was used as an adsorbent for removing methylene blue (MB) dye in single- and multi-dye systems. BET, SEM, FTIR, XRD, and TEM were used to characterize AGA to elucidate its morphology, composition and physicochemical properties. According to the results, 1.25 g/L AGA adsorbed 99 % of 10 mg/L MB in 3 h in a single-dye system. The removal efficiency decreased to 97.2 % in the presence of 10 mg/L Cu2+ ions and 40.2 % when the solution salinity increased to 70 %. In a single-dye system, the experimental data do not match well with the Freundlich isotherm, pseudo-first order, and the Elovich kinetic model, however, in a multi-dye system, it fit well with both extended Langmuir and the Sheindorf-Rebhun-Sheintuch. Notably, AGA removed 66.87 mg/g in a dye solution containing only MB, whereas 50.14-60.01 mg/g adsorption of MB was accomplished in a multiple-dye system. According to the molecular docking analysis, the dye removal process involved chemical bonds between the functional groups of AGA and the dye molecules, hydrogen bonds, hydrophobic and electrostatic interactions. The overall binding score of MB decreased from -26.9 kcal/mol in a single-dye system to -18.3 kcal/mol in a ternary system.

Adsorptive and photocatalytic degradation potential of porous polymeric materials for removal of pesticides, pharmaceuticals, and dyes-based emerging contaminants from water

Life on earth is dependent on clean water, which is crucial for survival. Water supplies are getting contaminated due to the growing human population and its associated industrialization, urbanization, and chemically improved agriculture. Currently, a large number of people struggle to find clean drinking water, a problem that is particularly serious in developing countries. To meet the enormous demand of clean water around the world, there is an urgent need of advanced technologies and materials that are affordable, easy to use, thermally efficient, portable, environmentally benign, and chemically durable. The physical, chemical and biological methods are used to eliminate insoluble materials and soluble pollutants from wastewater. In addition to cost, each treatment carries its limitations in terms of effectiveness, productivity, environmental effect, sludge generation, pre-treatment demands, operating difficulties, and the creation of potentially hazardous byproducts. To overcome the problems of traditional methods, porous polymers have distinguished themselves as practical and efficient materials for the treatment of wastewater because of their distinctive characteristics such as large surface area, chemical versatility, biodegradability, and biocompatibility. This study overviews improvement in manufacturing methods and the sustainable usage of porous polymers for wastewater treatment and explicitly discusses the efficiency of advanced porous polymeric materials for the removal of emerging pollutants viz. pesticides, dyes, and pharmaceuticals whereby adsorption and photocatalytic degradation are considered to be among the most promising methods for their effective removal. Porous polymers are considered excellent adsorbents for the mitigation of these pollutants as they are cost-effective and have greater porosities to facilitate penetration and adhesion of pollutants, thus enhance their adsorption functionality. Appropriately functionalized porous polymers can offer the potential to eliminate hazardous chemicals and making water useful for a variety of purposes thus, numerous types of porous polymers have been selected, discussed and compared especially in terms of their efficiencies against specific pollutants. The study also sheds light on numerous challenges faced by porous polymers in the removal of contaminants, their solutions and some associated toxicity issues.

Cage-Based Covalent Organic Framework for the Effective and Efficient Removal of Malachite Green from Wastewater

A cage-covalent organic framework (COF)-TP {T = bis(tetraoxacalix[2]arene[2]triazine); P = piperazine}, a novel two-dimensional covalent organic skeleton substituted with a nucleophilic cyanuric chloride analogue, was synthesized by a simple polymerization process. Cage-COF-TP is advantageous owing to its good structural order, permanent porosity, and low preparation cost. This skeleton was employed as a cost-effective adsorbent for the intermittent adsorption of an organic dye from aqueous solutions. Adsorption experiments were carried out at different initial dye concentrations, contact times, and solution pH. The adsorption kinetics followed the pseudo-second order model, and the results of thermodynamic studies were consistent with the Langmuir isotherm model. The high degree of matching between the size and shape of malachite green (MG) and the shrunken channels present in Cage-COF-TP were responsible for the enhanced adsorption ability of this material. Furthermore, theoretical calculations indicated that the high adsorption of the studied adsorbent can be attributed to the presence of nitrogen-rich triazine units in the Cage-COF-TP, which are expected to strengthen its affinity to guest molecules. The obtained results showed that the developed adsorbent is an efficient adsorbent that is theoretically capable of stimulating the removal of ∼2000 mg/g MG from wastewater at ambient temperature. This study will therefore be expected to promote the development of new functional materials based on COFs.

Chemical analysis of low carbon content coals and their applications as dye adsorbent

Coal is primarily a fuel material but lately it has been utilized as an adsorbent for removing toxic metal ions. However, its usage for removing organic pollutants is not well studied. We report here a systematic study on the use of coal samples of varying carbon contents as adsorbents for removing Basic Blue 41 as a model cationic dye. The coal samples were collected from coal mines and were thoroughly characterized. The concentrations of carbon, hydrogen, oxygen, nitrogen and sulphur contents were measured by CHNS analyzer. The concentrations of aluminum, silicon, sulphur, titanium and iron were determined by EDXRF, which corresponded to silicon dioxide (quartz) and aluminium silicate (kaolinite) as the major mineral inclusions, corroborated by XRD results and micrographs showing elemental maps determined from SEM-EDAX. The coal samples with low carbon content revealed higher adsorption capacity (q_e ∼ 8.0-9.3 mg/g) of Basic Blue dye at optimized adsorbent dose (2 mg/mL), pH 9 and contact time (120 min). The adsorption kinetic studies satisfied pseudo second order model and the intra-particle diffusion of the dye was evident. The dye adsorption followed Langmuir adsorption isotherm, and the q_max values ranged between 17 and 30 mg/g for low carbon content coal. The FT-IR, Brunauer-Emmett-Teller (BET) surface area and zeta potential results of the coal samples could explain the adsorption phenomenon of cationic dye. The kinetic and thermodynamic studies revealed that the adsorption of Basic Blue 41 dye was based on chemisorptions mechanism.

An Overview on Composite Sorbents Based on Polyelectrolytes Used in Advanced Wastewater Treatment

Advanced wastewater treatment processes are required to implement wastewater reuse in agriculture or industry, the efficient removal of targeted priority and emerging organic & inorganic pollutants being compulsory (due to their eco-toxicological and human health effects, bio-accumulative, and degradation characteristics). Various processes such as membrane separations, adsorption, advanced oxidation, filtration, disinfection may be used in combination with one or more conventional treatment stages, but technical and environmental criteria are important to assess their application. Natural and synthetic polyelectrolytes combined with some inorganic materials or other organic or inorganic polymers create new materials (composites) that are currently used in sorption of toxic pollutants. The recent developments on the synthesis and characterization of composites based on polyelectrolytes, divided according to their macroscopic shape-beads, core-shell, gels, nanofibers, membranes-are discussed, and a correlation of their actual structure and properties with the adsorption mechanisms and removal efficiencies of various pollutants in aqueous media (priority and emerging pollutants or other model pollutants) are presented.

Green fabrication of porous microspheres containing cellulose nanocrystal/MnO2 nanohybrid for efficient dye removal

Microspheres based on cellulose nanocrystal (CNC)/metal oxide hybrid materials have great application prospects in wastewater treatment due to simultaneously adsorption, degradation ability, easily separation and recycling properties. However, the relatively small porosity and specific surface area of the CNC-based microspheres limit their adsorption ability. Herein, we reported a facile strategy to prepare porous microsphere based on CNC/MnO₂ by freeze-drying the air-bubble templated emulsion, in which the sodium alginate (SA) was used as the crosslinked matrix. Thus-obtained CNC/MnO₂/SA microspheres showed low density of 0.027 g/cm³ and high porosity of 98.23%. Benefiting from the high porosity, synergetic effect of CNC electrostatic adsorption and oxidative degradation ability of MnO₂, the decolorization ratio of methylene blue (800 mg/mL) could be up to 95.4% in 10 min, and the equilibrium decolorization could reach 114.5 mg/g. This study provides a green and facile strategy to design porous CNC-based material for dye wastewater treatment.