Surface hydrolysis of postconsumer polyethylene terephthalate to produce adsorbents for cationic contaminants

Abstract

In this work, the surface hydrolysis of postconsumer polyethylene terephthalate (PET) was used to produce an ion exchange material to adsorb cationic contaminants from water. The PET surface hydrolyses were carried out in neutral, alkaline, and acid media (NaOH or HNO 3 at 7, 10, and 15 mol L À1) under reflux producing surface carboxylic acid sites (À ÀCOOH) characterized by ATR-IR, pyridine adsorption, titration, TG, and DSC analyses. Acid hydrolysis produced high concentrations of À ÀCOOH (up to 0.5 mmol g À1 PET ), whereas no significant concentration of carboxylic acid sites was obtained by neutral and alkaline hydrolysis. SEM analyses suggest that the acid sites are likely located at the cracks and defects produced on the PET surface by acid hydrolysis. Neutral or alkaline hydrolysis produced a very regular and smooth PET surface with very low acid site concentrations. The adsorption isotherms of Cd þ2 as a model of heavy metal and the dye methylene blue as a model of large organic cationic molecules showed high adsorption capacities for the HNO 3 -hydrolyzed PET, whereas no adsorption takes place on the neutral-or alkaline-hydrolyzed polymer.

Polysaccharide polyelectrolyte multilayer coating on poly(ethylene terephthalate)

“…The non‐uniform erosion observed for shorter treatment time (Fig. (B)) has been ascribed to the faster detachment of amorphous region in comparison with crystalline domains . Thus, the formation of larger pores for longer hydrolysis times (Fig.…”

“…2(B)) has been ascribed to the faster detachment of amorphous region in comparison with crystalline domains. 33 Thus, the formation of larger pores for longer hydrolysis times ( Fig. 2(C)) has been related to the removal of crystallites from the crystalline regions.…”

Degradation and Recyclability of Poly (Ethylene Terephthalate)

“…State of the art recycling technology by M/s Teijin Limited, Osaka, Japan , has won the Honor award [44]. By this technology, valuable materials are recovered from PET bottles wastes which are crushed, washed and then dissolved in ethylene glycol at its boiling point under pressure of 1 bar to depolymerize to BHET which is later reacted with methanol in an efficient way to produce dimethyl terephthalate and ethylene glycol by ester exchange reaction at the boiling point of methanol.…”

Recycling of poly(ethylene terephthalate) – A review focusing on chemical methods

“…Reaction times are between 6 minutes and 70 hours ( Table 2). The general reaction scheme of alkaline hydrolysis is depicted in Figure 4 [162][163][164][165][166][167][168][169][170][171]. Caparanga et al [162] used alkaline washing as pretreatment of PET-waste before actual recycling.…”

“…Although Khalaf and Hasan as well as Paliwal and Mungray used a catalyst (tetra butyl ammonium bromide, tetra butyl ammonium iodide), their TPA yield of 99% was not significantly greater than the yield of Shafique et al [168] with 96%. Finally, Rosmaninho et al [169] used alkaline hydrolysis for surface modification of PET not to yield PET monomers but to synthesize a cation exchange material as adsorbent for cationic contaminants. They compared this procedure with an acid surface modified PET.…”