Graphene Oxide-Crospolyvinylpyrrolidone Hybrid Microspheres for the Efficient Adsorption of 2,4,6-Trichlorophenol

Removal and detection of phenols through an SPE-HPLC method using microporous organic networks as adsorbent

The design and development of a facile synthesis approach to construct novel materials for the rapid adsorption and removal of environmental pollutants are of significant interest. In this work, we report the rational design and facile synthesis of magnetic core-shell-based microporous organic networks, Fe3O4@MON-TBPT-TEB (TTMON, achieved by reacting 2,4,6-tris(p-bromophenyl) triazine and 1,3,5-triethynylbenzene) and Fe3O4@MON-TBPM-DEBP (TDMON, achieved by reacting tetrakis (4-bromophenyl) methane and 4-4'-diethynylbiphenyl). These MONs possessed excellent dispersity, electrostatic attraction as well as plenty of π-π and hydrophobic interaction sites enabled them to efficiently absorb targeted environmental pollutants. TTMON and TDMON exhibited excellent adsorption capacities of 440 and 510 mg g-1, respectively, at 25 °C for 2,4,6-trichlorophenol (TCP). TCP, 2,4-dichlorophenol (DCP), 2-naphthol (2-NT) and 4-nitrophenol (4-NP) from aqueous solution were treated by both MONs, followed by their analysis with high-performance liquid chromatography (HPLC). For TDMON, the proposed SPE-HPLC-UV method showed an LOD of 0.03 μg L-1, LOQ of 0.11 μg L-1, and a wide linear range of 1-1000 μg L-1 for TCP. The adsorption kinetics, thermodynamics, isotherms, effect of pH and humic acid (HA), ionic strength, regeneration, and reusability of the MONs were also studied. The results revealed that the novel-designed MONs have potential applications as efficient adsorbents in sample pretreatment.

Bioremediation of 2,4,6-trichlorophenol by extracellular enzymes of white rot fungi immobilized with sodium alginate/hydroxyapatite/chitosan microspheres

Hydroxyapatite, a calcium phosphate biomass material known for its excellent biocompatibility, holds promising applications in water, soil, and air treatment. Sodium alginate/hydroxyapatite/chitosan (SA-HA-CS) microspheres were synthesized by cross-linking sodium alginate with calcium chloride. These microspheres were carriers for immobilizing extracellular crude enzymes from white rot fungi through adsorption, facilitating the degradation of 2,4,6-trichlorophenol (2,4,6-TCP) in water and soil. At 50 °C, the immobilized enzyme retained 87.2% of its maximum activity, while the free enzyme activity dropped to 68.86%. Furthermore, the immobilized enzyme maintained 68.09% of its maximum activity at pH 7, surpassing the 51.16% observed for the free enzyme. Under optimal conditions (pH 5, 24 h), the immobilized enzymes demonstrated a remarkable 94.7% removal rate for 160 mg/L 2,4,6-TCP, outperforming the 62.1% achieved by free crude enzymes. The degradation of 2,4,6-TCP by immobilized and free enzymes adhered to quasi-first-order degradation kinetics. Based on LC-MS, the plausible biodegradation mechanism and reaction pathway of 2,4,6-TCP were proposed, with the primary degradation product identified as 1,2,4-trihydroxybenzene. The immobilized enzyme effectively removed 72.9% of 2,4,6-TCP from the soil within 24 h. The degradation efficiency of the immobilized enzyme varied among different soil types, exhibiting a negative correlation with soil organic matter content. These findings offer valuable insights for advancing the application of immobilized extracellular crude enzymes in 2,4,6-TCP remediation.

Catechol-Based Porous Organic Polymers for Effective Removal of Phenolic Pollutants from Water

Phenolic pollutants released from industrial activities seriously damage natural freshwater resources, and their elimination or reduction to safe levels is an urgent challenge. In this study, three catechol-based porous organic polymers, CCPOP, NTPOP, and MCPOP, were prepared using sustainable lignin biomass-derived monomers for the adsorption of phenolic contaminants in water. CCPOP, NTPOP, and MCPOP showed good adsorption performance for 2,4,6-trichlorophenol (TCP) with theoretical maximum adsorption capacities of 808.06 mg/g, 1195.30 mg/g, and 1076.85 mg/g, respectively. In addition, MCPOP maintained a stable adsorption performance after eight consecutive cycles. These results indicate that MCPOP is a potential material for the effective treatment of phenol pollutants in wastewater.

Graphene-based materials for effective adsorption of organic and inorganic pollutants: A critical and comprehensive review

Water scarcity has been felt in many countries and will become a critical issue in the coming years. The release of toxic organic and inorganic contaminants from different anthropogenic activities, like mining, agriculture, industries, and domestic households, enters the natural waterbody and pollutes them. Keeping this in view in combating the environmental crises, removing pollutants from wastewater is one of the ongoing environmental challenges. Adsorption technology is an economical, fast, and efficient physicochemical method for removing both organic and inorganic pollutants, even at low concentrations. In the last decade, graphene and its composite materials have become the center of attraction for numerous applications, including wastewater treatment, due to the large surface area, highly active surface, and exclusive physicochemical properties, which make them potential adsorbents with unique physicochemical properties, like low density, chemical strength, structural variability, and the possibility of large-scale fabrications. This review article provides a thorough summary/critical appraisal of the published literature on graphene-, GO-, and rGO-based adsorbents for the removal of organic and inorganic pollutants from wastewater. The synthesis methods, experimental parameters, adsorption behaviors, isotherms, kinetics, thermodynamics, mechanisms, and the performance of the regeneration-desorption processes of these substances are scrutinized. Finally, the research challenges, limitations, and future research studies are also discussed. Certainly, this review article will benefit the research community by getting substantial information on suitable techniques for synthesizing such adsorbents and utilizing them in water treatment and designing water treatment systems.

Characteristics of ball-milled PET plastic char for the adsorption of different types of aromatic organic pollutants

Ball-milled plastic char (BMPC) was manufactured by ball-milling of native plastic char (PC) that was synthesized via slow pyrolysis of polyethylene terephthalate (PET) water bottle waste, and its adsorption characteristics of aqueous phenanthrene (PHE), phenol, and 2,4,6-trichlorophenol (2,4,6-TCP) and its possible mechanisms were investigated. With the increase of PC pyrolysis temperature, the specific surface area of BMPC increased obviously, forming larger functional groups compared to PC. Boehm titration showed that total acidic groups of BMPC decreased significantly with the increase of pyrolysis temperature. The sorption kinetics of three adsorbates was adequately simulated by pseudo-second-order model (R² > 0.99). Langmuir model fitted well the adsorption isotherms of PHE and phenol, while Freundlich model simulated the adsorption isotherm of 2,4,6-TCP better. The adsorption amount of PHE, phenol, and 2,4,6-TCP increased significantly as the pyrolysis temperature increased. The maximum BMPC adsorption capacity reached 21.9 mg·g^-1 (for PHE), 106 mg·g^-1 (for phenol), and 303 mg·g^-1 (for 2,4,6-TCP) at 25 °C in aqueous solution. FTIR analysis suggested that surface sorption-based π-π interaction was a dominant mechanism of PHE adsorption; meanwhile, H-bonding between O-containing groups on BMPC and hydroxyl groups of adsorbates was responsible for phenol and 2,4,6-TCP removal. This paper shows that BMPC can be used as adsorbent for treating aromatic compounds in aqueous environment and has an economic worth of application.

Adsorption and Photocatalytic Degradation of Pesticides into Nanocomposites: A Review

The extensive use of pesticides in agriculture has significantly impacted the environment and human health, as these pollutants are inadequately disposed of into water bodies. In addition, pesticides can cause adverse effects on humans and aquatic animals due to their incomplete removal from the aqueous medium by conventional wastewater treatments. Therefore, processes such as heterogeneous photocatalysis and adsorption by nanocomposites have received special attention in the scientific community due to their unique properties and ability to degrade and remove several organic pollutants, including pesticides. This report reviews the use of nanocomposites in pesticide adsorption and photocatalytic degradation from aqueous solutions. A bibliographic search was performed using the ScienceDirect, American Chemical Society (ACS), and Royal Society of Chemistry (RSC) indexes, using Boolean logic and the following descriptors: "pesticide degradation" AND "photocatalysis" AND "nanocomposites"; "nanocomposites" AND "pesticides" AND "adsorption". The search was limited to research article documents in the last ten years (from January 2012 to June 2022). The results made it possible to verify that the most dangerous pesticides are not the most commonly degraded/removed from wastewater. At the same time, the potential of the supported nanocatalysts and nanoadsorbents in the decontamination of wastewater-containing pesticides is confirmed once they present reduced bandgap energy, which occurs over a wide range of wavelengths. Moreover, due to the great affinity of the supported nanocatalysts with pesticides, better charge separation, high removal, and degradation values are reported for these organic compounds. Thus, the class of the nanocomposites investigated in this work, magnetic or not, can be characterized as suitable nanomaterials with potential and unique properties useful in heterogeneous photocatalysts and the adsorption of pesticides.

Removal of hazardous dyes, toxic metal ions and organic pollutants from wastewater by using porous hyper-cross-linked polymeric materials: A review of recent advances

Water quality plays a central role in the well-being of all the living organisms on planet Earth. The ever-increasing human population and consequently increasing industrialization, urbanization, and chemically boosted cultivation are rapidly contaminating already stressed water resources. The availability of clean drinking water has become scarce for masses across the globe, and this situation is becoming alarming in developing countries. Therefore, the immediate need for cost-effective, easily accessible, eco-friendly, portable, thermally efficient, and chemically stable technologies and materials is desperately felt to meet the high global demand for clean water. To search for effective materials for wastewater treatment, the hyper-cross-linked porous polymers (HCPs) have emerged as an excellent class of porous materials for wastewater treatment due to their unique features of high surface area, tunability, biodegradability, and chemical versatility. This review describes the advances in fabrication strategies and the efficient utilization of hyper-cross-linked porous polymers for wastewater treatment. Moreover, this review specifically discusses the hyper-cross-linked porous polymers effectiveness for the separation of the dyes, nutrients, inorganic ions, organic contaminants, and toxic metals ions. Finally, the review provides insight into the challenges and prospects in the area of hyper-cross-linked porous polymers. Overall, the hyper-cross-linked porous polymers with empowering proper functionalization can provide an opportunity for the wastewater treatment not only to remove toxic contaminants but also to make contaminated water useful for various applications.