Separation of polyvinylchloride and acrylonitrile-butadiene-styrene combining advanced oxidation by S2O82-/Fe2+ system and flotation.

A combining technology of advanced oxidation by S2O82-/Fe2+ system and flotation was proposed for separating polyvinyl chloride (PVC) and acrylonitrile butadiene styrene (ABS). In this research, sodium persulfate was activated by heating and ferrous ions. The separation efficiency of PVC/ABS oxidized by S2O82-/Fe2+ was higher than that by sodium persulfate. The mechanism of this process was investigated through contact angle, Fourier transform infrared spectroscopy (FT-IR) inductively coupled plasma (ICP), nuclear magnetic resonance (NMR) and X-ray photoelectron spectroscopy (XPS). The floatability of ABS reduced owing to the introduction of oxygen-containing functional groups such as carbonyl (OCO) and hydroxyl (OH), which was a result of oxidation by sulfate radicals (SO4·-). The optimal conditions for separating PVC and ABS were: Na2S2O8 concentration 0.1 M, molar ratio (S2O82-/Fe2+) 200, treatment time 10 min, flotation time 4 min, frother concentration 14.7 mg L-1 and airflow rate 6.8 mL min-1. Novel kinetics of pretreatment time and flotation were proposed and researched in this work. The max rate constant of PVC/ABS flotation was 0.64 min-1. In addition, the pretreatment solution can be reused for three times with superior performance. The recovery and purity of PVC reached 100% and 99.7%, respectively. According to reasonable evaluation, the combination of S2O82-/Fe2+ advanced oxidation and flotation is a practical and efficient technology for separating PVC and ABS.

Combination of sodium hypochlorite pretreatment and flotation towards separation of polycarbonate from waste plastic mixtures.

This study developed a novel method, surface pretreatment using sodium hypochlorite along with flotation, to facilitate separation of waste polycarbonate from plastic mixtures for recycling. Surface pretreatment was observed that has an obviously negative effect on the floating ratio of polycarbonate and the floating ratio of poly-methyl-methacrylate, polystyrene, and polyvinylchloride was not affected in flotation, and this difference in floating ratio can be expected to separate polycarbonate from plastic mixtures. The optimum conditions obtained included sodium hypochlorite concentration of 0.05 M, pretreatment temperature of 70.0 °C, pretreatment time of 60.0 min, frother dosage of 10.8 mg/L, and flotation time of 4.0 min. Under optimum conditions, polycarbonate was separated effectively from multiple plastic mixtures, and the purity and recovery were 99.8% and 100.0%, respectively. The major mechanism of surface pretreatment was ascertained by the aid of Fourier transform infrared, scanning electron microscope, energy dispersive spectrometer, and X-ray photoelectron spectroscopy, and the hydrophilic groups, pitting, and protuberances introduced on polycarbonate surface caused the reduced floating ratio of polycarbonate. Accordingly, this method can be expected to improve the recycling quality of waste plastics, and provides technological insights in the environmentally friendly disposal of waste plastics.

Application of surface modification using sodium hypochlorite for helping flotation separation of acrylonitrile-butadiene-styrene and polystyrene plastics of WEEE.

Acrylonitrile-butadiene-styrene (ABS) and polystyrene (PS), as important fractions of Waste from Electric and Electronic Equipment (WEEE) plastics, show great significances to the recycling of WEEE. The objective of this study is to develop a simple, practical and efficient surface modification method using sodium hypochlorite (NaClO) for separation of waste ABS and PS plastics by the aid of froth flotation. After surface modification, more hydrophilic groups are introduced on ABS surface than that of PS, enhancing its surface hydrophilicity clearly and reducing its recovery in floated products. Single parameter experiments demonstrate NaClO concentration, treatment temperature, treatment time are key parameters in surface modification. Optimization of conditions for surface modification of ABS was conducted by Response Surface Methodology with a Box-Behnken design, and a predicting model was obtained also. The optimum conditions are NaClO concentration of 0.05 M/L, temperature of 67.50 °C, treatment time 59.50 min and stirring rate of 200 rpm. Under optimum conditions, ABS and PS with different particle sizes can be separated efficiently with recovery of 99.18% and 99.47%, and purity of 99.45% and 99.18% respectively. The application of surface modification using sodium hypochlorite can facilitate efficient flotation separation of waste ABS and PS plastics for the recycling of WEEE.

Preparation and performance of a pH-sensitive cisplatin-loaded magnetic nanomedicine that targets tumor cells via folate receptor mediation.

The present study aimed to prepare cisplatin (CDDP)-loaded magnetic nanoparticles (MNPs), which target folate receptors via a pH-sensitive release system (FA­PEG­NH­N=MNPs­CDDP). This is of interest for the development of intelligent drug delivery systems that target tumors of the head and neck. The chemical coprecipitation method was used to prepare ferroferric oxide MNPs. These were modified with aldehyde sodium alginate complexed with the chemotherapeutic agent, CDDP on the surface of the nanoparticles. Double hydrazine­poly(ethylene glycol; PEG) was also prepared by attaching the carboxyl group of hydrazine­folate on one side of the double hydrazine­PEG, obtaining folate­hydrazine­PEG­diazenyl. This binds the aldehyde group of sodium alginic acid on the MNP to enclose CDDP, in order that it is sequestered within the carrier. This method obtained a pH­sensitive, FA­modified CDDP­loaded MNP (FA­PEG­NH­N=MNPs­CDDP), which acts as an intelligent tumor targeting drug delivery system. The mean size of the MNPs was ~10.2±1.5 nm, the mean hydrodynamic diameter detected by laser particle sizing instruments was 176.6±1.1 nm, and the ζ­potential was ­20.91±1.76 mV. The CDDP content was 0.773 mg/ml, the iron content was ~1.908 mg/ml and the maximum saturation magnetization was 16.3±0.2 emu/g. The current study produced a pH­sensitive FA­modified CDDP­loaded MNP that is stable and exhibits magnetic responsiveness, which releases CDDP in a low pH environment.

MWNT-hybrided supramolecular hydrogel for hydrophobic camptothecin delivery.

To encapsulate the hydrophobic camptothecin (CPT) into hydrogel matrix with a high loading amount, a supramolecular hydrogel hybrided with multi-walled carbon nanotubes (MWNTs) was developed by the host-guest interactions and used for loading and delivering CPT. Firstly, carboxylated MWNTs were modified by polyethylene glycol monomethyl ether (MPEG), which resulted in the water-dispersed MPEG-MWNTs. Then α-cyclodextrin (α-CD) was mixed with MPEG-MWNTs and the hybrid supramolecular hydrogel was fabricated by the inclusion interactions between α-CD and MPEG. The used MPEG not only dispersed MWNTs in aqueous solution, but also functioned as hydrogel matrix by interacting with α-CD. The gelation time for the sol-gel transition and rheological properties of the resultant hydrogels were studied. Due to the excellent application of MWNTs in drug delivery, hydrophobic CPT could be loaded into the hydrogel matrix by a higher amount compared with micelles. By in vitro release and cell viability tests, it was found that the encapsulated CPT could exhibit a controlled and sustained release behavior as well as sustained antitumor efficacy.