Search

Recovery of plastic waste has a positive influence on solid waste management as it can bring new life to plastic waste. Hydrolysis treatment is one of the approaches for plastic waste recovery, in which plastic monomer can be recovered through depolymerisation. This study explored the recovery of polyethylene terephthalate (PET) plastic in nitric acid and leachate. The weight changes were analysed in PET when exposed to different hydrolysis agents (nitric acid and leachate) at different reaction times and temperatures. The monomer recovery of PET, known as terephthalic acid (TPA), was also evaluated. It was found that high temperatures and reaction times promoted to the high recovery of TPA. The PET residue measured as weight difference was found in line with the trend of TPA yield. The hydrolysis using nitric acid can recover more TPA than the leachate system. The knowledge obtained from this study would be beneficial in upcycling plastic waste into high-value end products.

TPA was synthesized by a two step reaction. Firstly, water-soluble coal acids (CA) was obtained by oxygen-oxidation at 260°C in all aqueous solution of potassium hydroxide, and then crud TPA was got by isomerization of the CA with the existence of CdCO3 catalyst and CO2 pressure. The optimum reaction conditions to get crude TPA were 4% amount of CdCO3 catalyst, and reacted at 420°C with initial 3.0MPa CO2 pressure. Pure TPA was obtained by a separation step and the yield of pure TPA is 37.16% (based on CA). Furthermore, DOTP was synthesized by the refined TPA and isooctanol. The influence of mole ratio of TPA and isooctanol, amount of catalyst and reaction time on the final yield of DOTP were discussed. The purity of TPA was detected by HPLC and DOTP was detected by FT-IR, 1H-NMR to get confirmatory results.

Self-assembly of terephthalic acid (TPA), vacuum deposited on Pt(111) supported graphene, has been investigated by scanning tunneling microscopy (STM). TPA organizes in an ordered 3 × 4 superstructure with respect to the graphene lattice. This structure is a consequence of hydrogen-bonded TPA chains that arrange in a commensurate overlayer on graphene. Due to the polycrystalline nature of graphene on Pt(111), the TPA layer exhibits various grain boundaries and dislocations. Molecular resolved STM imaging has been used to characterize these defect structures in the TPA monolayer.

Chemical depolymerization of poly(ethylene terephthalate) (PET) waste is a possible remedy to huge amount of solid waste generation as it results in degradation products that possess a potential of recyclability. PET bottle waste was depolymerized by aminolysis using diethanolamine. Novel synthesis of N1, N1,N4,N4-tetrakis (2-hydroxyethyl) terephthalamide (THETA) with 73-76% yield and terephthalic acid (TPA) with 78-82% yield was achieved. The purified products were analyzed by FTIR, melting point, DSC, DTG and 1H-NMR. THETA has various applications in the synthesis of rigid polyurethane foam, unsaturated polyester resins and also as a cross linking agent/ hardener for epoxy resins.

This study introduces a low temperature surfactant-free hydrothermal method to synthesize mesoporous Nb2O5 photocatalysts using NbCl5 and H2O2 as precursors that are subsequently calcinated at 300, 400 and 450 °C and are assigned as mNb2O5-300, mNb2O5-400 and mNb2O5-450, respectively. Commercial niobia sample was used as reference sample for comparison purpose. All of materials were characterized by XRD, SEM, UV–Vis DRS, FTIR, TG/DTG and BET techniques. The synthesized Nb2O5 particles especially mNb2O5-300 sample shows a high surface area (240 m2/g), a large pore volume (0.21 cm3/g) and an identifying morphology of these features. Photocatalytic decomposition of terephthalic acid was evaluated using UV–Vis spectrophotometer. The photocatalytic reactions followed pseudo-first-order kinetics with an apparent rate constant of k = 105 × 10−3 min−1 for mNb2O5-300 sample with the highest activity among all samples at natural pH (pH = 6). Meanwhile, it was observed that optimum pH of 4 resulted in fast photocatalytic reaction for mNb2O5-300 sample.

Terephthalic acid (TPA) is widely applied as a raw material in making polyester fiber, polyethylene terephthalate (PET) bottles, polyester films, etc. TPA is toxic and is known to act as endocrine disruptor. TPA wastewater is traditionally treated by biological process and this study aims to evaluate the effectiveness of several advanced oxidation processes on TPA removal. The oxidation processes studied were: UV–TiO 2 , UV–H 2 O 2 , UV–H 2 O 2 –Fe, O 3 , O 3 /Fe, O 3 /TiO 2 , UV–O 3 –H 2 O 2 –Fe and UV–O 3 –H 2 O 2 –Fe–TiO 2 . The results indicate that the time required for the complete destruction of 50 ppm of TPA can be minimized from 10 h using UV–TiO 2 system, to less than 10 min by UV–H 2 O 2 –Fe–O 3 system. Some of the likely organic intermediates identified during TPA destruction include, benzoquinone, benzene, maleic acid and oxalic acid. Possible destruction pathway of TPA has been proposed. TPA degradation by various systems was also analyzed based on the reaction kinetics and operating costs.

Polyethylene terephthalate, a copolymer of terephthalic acid (TPA) or dimethyl terephthalate (DMT) with ethylene glycol, has food, beverage, and drinking water contact applications. Di-2-ethylhexyl terephthalate (DEHT) is a plasticizer in food and drinking water contact materials. Oral reference doses (RfDs) and total allowable concentrations (TACs) in drinking water were derived for TPA, DMT, and DEHT. Category RfD and TAC levels were also established for nine C(1)-C(8) terephthalate esters. The mode of action of TPA, and of DMT, which is metabolized to TPA, involves urinary acidosis, altered electrolyte elimination and hypercalciuria, urinary supersaturation with calcium terephthalate or calcium hydrogen terephthalate, and crystallization into bladder calculi. Weanling rats were more sensitive to calculus formation than dams. Calculi-induced irritation led to bladder hyperplasia and tumors in rats fed 1000 mg/kg-day TPA. The lack of effects at 142 mg/kg-day supports a threshold for urine saturation with calcium terephthalate, a key event for calculus formation. Chronic dietary DMT exposure in rodents caused kidney inflammation, but not calculi. Chronic dietary DEHT exposure caused general toxicity unrelated to calculi, although urine pH was reduced suggesting the TPA metabolite was biologically-active, but of insufficient concentration to induce calculi. Respective oral reference doses of 0.5, 0.5, and 0.2 mg/kg-day and total allowable drinking water concentrations of 3, 3, and 1 mg/L were derived for TPA, DMT, and DEHT. An oral RfD of 0.2 mg/kg-day for the terephthalate category chemicals corresponded to a drinking water TAC of 1 mg/L.