Green valorization of PET waste into functionalized Cu-MOF tailored to catalytic reduction of 4-nitrophenol

Synthesis of Co3Fe7/CoFe2O4 incorporated porous carbon catalysts via molten salt method: applications in the oxygen reduction reaction and 4-nitrophenol reduction

Developing high-performance, multifunctional non-precious metal catalysts is essential for enhancing the efficiency of future energy utilization. In this study, four types of magnetic, recyclable Co3Fe7/CoFe2O4 incorporated porous carbon composite catalysts were synthesized using citric acid as the carbon source and ammonium chloride (NH4Cl) as the salt medium. Iron and cobalt salts, in four different proportions, were uniformly incorporated using freeze-drying technology and subsequently processed through in situ calcination. Among the synthesized catalysts, Co3Fe7/CoFe2O4@NC-1, demonstrated outstanding catalytic reduction performance, with a reaction rate constant (k) of 0.031 min-1, along with excellent cycle stability for 4-NP. The resulting Co3Fe7/CoFe2O4@NC-3 catalyst exhibited good ORR activity in an alkaline medium (E onset = 0.99 V, E 1/2 = 0.83 V, J L = -5.2 mA cm-2), along with long-term durability and resistance to methanol poisoning. These hybrid materials hold promise as non-precious metal electrocatalysts for fuel cell ORRs and introduce a new class of catalytic candidates for 4-NP reduction.

Controlled bioreduction of silver ions to nanosized particles on a porous magnetic-biopolymer of carboxymethyl cellulose, Fe3O4/CMC-Ag NPs, serving as a sustainable nanocatalyst

A magnetic-biopolymer composite of carboxymethyl cellulose (CMC), designated as Fe3O4@CMC, was synthesized featuring remarkable stability and an active surface with a green biosynthetic method. This composite was engineered to serve as a substrate for stabilizing silver nanoparticles (Ag NPs) with enhanced functional properties. The catalytic efficacy of the nanocatalyst, incorporating Ag NPs at concentrations of 3%, 7%, and 10%, was evaluated for the reduction of the toxic compound 4-nitrophenol to the beneficial 4-aminophenol. Among the tested configurations, the formulation containing 10% silver nanoparticles, in conjunction with Euphorbia plant extract as a bioreducing agent, exhibited the highest reduction efficiency and favorable reaction kinetics, rendering it the optimal choice. The apparent rate constant (K app) was assessed by fine-tuning the catalyst parameters, while the reaction mechanism was further elucidated by adjusting the concentrations of NaBH4 and 4-nitrophenol. Notably, the catalyst demonstrated good stability over five consecutive reduction cycles and could be easily retrieved from the reaction mixture using an external magnet.

Innovative approaches to chemical recycling of polyethylene terephthalate waste: Investigating key components and their emerging applications

Polyethylene Terephthalate, a widely recognized thermoplastic, is used in numerous sectors including packaging, textiles, electronics, construction, and medical due to its lightweight, cost-efficiency, transparency, flexibility, quick drying, durability and excellent gas/moisture barrier properties. However, its non-biodegradable nature poses significant environmental concerns, necessitating effective recycling and reuse methods. Over the past decades, scientists have focused on both mechanical and chemical recycling methods for PET waste to produce new molecules with potential applications. This review provides a comprehensive account of utilizing PET waste as a feedstock for synthesizing new molecules through various recycling techniques. An up-to-date and comparative overview of different chemical recycling techniques, including ammonolysis, aminolysis, glycolysis, alcoholysis, and hydrolysis in terms of reactants, reaction conditions, products, and yields are outlined. Applications of depolymerized end products like terephthalamide, NN'-bisallyl-terephthalamide, terephthalic dihydrazide, NN'-diphenyl-terephthalamide, dimethyl-terephthalate, dimethyl terephthalate, bis-hydroxyethyl-terephthalate (BHET), bis-hydroxy ethylene terephthalamide (BHETA), terephthalic acid etc. are succinctly presented. These products found potential industrial applications including thermostabilizers, surfactants, hardeners, peptisers, photoinitiators, crosslinkers, plasticizers, adsorbents, sealants, catalysts, etc. Additionally, the conversion of these depolymerized end products into other useful compounds like terephthalonitrile, para-xylylenediamine, 1,4-bis(aminomethyl)cyclohexane, lanthanum complexes, acrylates, BHET and BHETA derivatives, oxadiazole derivatives, 2,2'-(1,4-phenylene)-bis(2-oxazoline), 1,4-cyclohexanedimethanol, dyes, dioctyl terephthalate, butylene-adipate-co-terephthalate, terephthaloyl dichloride etc. has also been detailed along with their potential applications.

Experimental investigation of zinc ferrite/insulation oil nanofluid natural convection heat transfer, AC dielectric breakdown voltage, and thermophysical properties

Improving the thermal and dielectric properties of insulation oil (INO) with nanoadditives is an important challenge, and achieving dispersion stability in these nanofluids is quite challenging, necessitating further investigation. The main goal of this study is the synthesis and use of the hydrophobicity of zinc ferrite (ZnFe2O4) nanoparticles, which can improve both the thermal and dielectric properties of the INO. This oil is made from distillate (petroleum), including severely hydrotreated light naphthenic oil (75-85%) and severely hydrotreated light paraffinic oil (15-25%). A comprehensive investigation was carried out, involving the creation of nanofluids with ZnFe2O4 nanoparticles at various concentrations, and employing various characterization methods such as X-ray diffraction (XRD), Fourier-transform infrared (FTIR), scanning electron microscopy, energy dispersive X-ray (EDX), zeta potential analysis, and dynamic light scattering (DLS). The KD2 Pro thermal analyzer was used to investigate the thermal characteristics, including the thermal conductivity coefficient (TCC) and volumetric heat capacity (VHC). Under free convection conditions, the free convection heat transfer coefficient (FCHTC) and Nusselt numbers (Nu) were evaluated, revealing enhancements ranging from 14.15 to 11.7%. Furthermore, the most significant improvement observed in the AC Breakdown voltage (BDV) for nanofluids containing 0.1 wt% of ZnFe2O4 amounted to 17.3%. The most significant finding of this study is the improvement in the heat transfer performance, AC BDV, and stability of the nanofluids.

Quaternization of a Triphenylamine-Based Conjugated Porous Organic Polymer to Immobilize PtCl62- for the Photocatalytic Reduction of 4-Nitrophenol

Photocatalytic reduction of 4-nitrophenol (4-NP) for converting it to nontoxic 4-aminophenol (4-AP) is one of the most efficient approaches for removing toxic 4-NP. Using porous organic polymers (POPs) as the support to immobilize noble metal catalysts has exhibited remarkable reduction performance but is rarely reported. Herein, a cationic triphenylamine-based POP was synthesized by quaternization to immobilize PtCl62- to prepare an efficient photocatalyst named DCM-TPA-Pt for the reduction of 4-NP to 4-AP in the presence of NaBH4. Different from reported methods which realize immobilization by doping or complexing, the support and PtCl62- are combined through electrostatic interaction with milder reaction conditions to produce a photocatalyst in this work. DCM-TPA-Pt shows excellent photocatalytic reduction performance, reaching 99.9% conversion within 3 min, and its pseudo-first-order constant is 0.0305 s-1, surpassing most of the reported photocatalysts. Moreover, DCM-TPA-Pt also exhibits equal reduction efficiency after five continuous cycles, which highlights its potential utilization in practical applications.

Waste treats waste: Facile fabrication of porous adsorbents from recycled PET and sodium alginate for efficient dye removal

Dye-contaminated water and waste plastic both pose enormous threats to human health and the ecological environment, and simultaneously solving these two issues in a sustainable and resource-saving way is highly important. In this work, a sodium alginate-polyethylene terephthalate-sodium alginate (SA@PET) composite adsorbent for efficient dye removal is fabricated using wasted PET bottle and marine plant-based SA via simple and energy-efficient nonsolvent-induced phase separation (NIPS) method. Benefiting from its porous structure and the abundant binding sites, SA@PET shows an excellent methylene blue (MB) adsorption capacity of 1081 mg g-1. The Redlich-Peterson model more accurately describes the adsorption behavior, suggesting multiple adsorption mechanisms. In addition to the electrostatic attractions of SA to MB, polar interactions between the PET matrix and MB are also identified as adsorption mechanisms. It is worth mentioning that SA@PET could be recycled 7 times without a serious decrease in performance, and the trifluoroacetic acid-dichloromethane solvent involved in the NIPS process has the possibility of reuse and stepwise recovery. Finally, the discarded adsorbent could be completely degraded under mild conditions. This work provides not only a composite adsorbent with excellent cationic dye removal performance for wastewater treatment, but also an upcycling strategy for waste PET.