Screening non-noble metal oxides to boost the low-temperature combustion of polyethylene waste in air

Globally,the efficient utilization of polymer wastes is one of the most important issues for current sustainable development topics.Herein,a green and efficient low-temperature combustion approach is proposed to deal with polymer wastes and recover heat energy,simultaneously alleviating the environment and energy crisis.Non-noble metal oxides(Al_(2)O_(3),Fe_(2)O_(3),NiO_(2),ZrO_(2),La_(2)O_(3)and CeO_(2)) were prepared,characterized and screened to boost the low-temperature combustion of polyethylene waste at 300℃ in air.The mass change,heat release and CO_(x) formation were studied in details and employed to evaluate the combustion rate and efficiency.It was found that CeO_(2)significantly enhanced the combustion rate and efficiency,which was respectively 2 and 7 times that of non-catalytic case.An interesting phenomenon was observed that the catalytic performance of CeO_(2) in polyethylene low-temperature combustion was significantly improved by the 7-day storage in the room environment or water treatment.XPS analysis confirmed the co-existence of Ce^(3+) and Ce^(4+) in CeO_(2),and the 7-day storage and water treatment promoted the amount of Ce^(3+),which facilitated the formation of the oxygen vacancies.That may be the reason why CeO_(2) exhibited excellent catalytic performance in polyethylene low-temperature combustion.

Adsorptive removal of hydrophobic organic compounds by carbonaceous adsorbents:A comparative study of waste-polymer-based,coal-based activated carbon,and carbon nanotubes

Adsorption of the hydrophobic organic compounds （HOCs） trichloroethylene （TCE）, 1,3-dichlorobenzene （DCB）, 1,3-dirdtrobenzene （DNB） and y-hexachlorocyclohexane （HCH） on five different carbonaceous materials was compared. The adsorbents included three polymer-based activated carbons, one coal-based activated carbon （F400） and multiwalled carbon nanotubes （MWNT）. The polymer- based activated carbons were prepared using KOH activation from waste polymers： polyvinyl chloride （PVC）, polyethyleneterephthalate （PET） and tire rubber （TR）. Compared with F400 and MWNT, activated carbons derived from PVC and PET exhibited fast adsorption kinetics and high adsorption capacity toward the HOCs, attributed to their extremely large hydrophobic surface area （2700 m2/g） and highly mesoporous structures. Adsorption of small-sized TCE was stronger on the tire-rubber-based carbon and F400 resulting from the pore-filling effect. In contrast, due to the molecular sieving effect, their adsorption on HCH was lower. MWNT exhibited the lowest adsorption capacity toward HOCs because of its low surface area and characteristic of aggregating in aqueous solution.

Occurrence,distribution,and potential influencing factors of sewage sludge components derived from nine full-scale wastewater treatment plants of Beijing,China

Millions of tons of waste activated sludge（WAS） produced from biological wastewater treatment processes cause severe adverse environmental consequences. A better understanding of WAS composition is thus very critical for sustainable sludge management. In this work, the occurrence and distribution of several fundamental sludge constituents were explored in WAS samples from nine full-scale wastewater treatment plants（WWTPs） of Beijing, China. Among all the components investigated, active heterotrophic biomass was dominant in the samples（up to 9478 mg/L）, followed by endogenous residues（6736 mg/L）,extracellular polymeric substances（2088 mg/L）, and intracellular storage products（464 mg/L）among others. Moreover, significant differences（p 〈 0.05） were observed in composition profiles of sludge samples among the studied WWTPs. To identify the potential parameters affecting the variable fractions of sludge components, wastewater source as well as design and operational parameters of WWTPs were studied using statistical methods. The findings indicated that the component fraction of sewage sludge depends more on wastewater treatment alternatives than on wastewater characteristics among other parameters. A principal component analysis was conducted, which further indicated that there was a greater proportion of residual inert biomass in the sludge produced by the combined system of the conventional anaerobic/anoxic/oxic process and a membrane bioreactor. Additionally, a much longer solids retention time was also found to influence the sludge composition and induce an increase in both endogenous inert residues and extracellular polymeric substances in the sludge.

Synthesis of linear low-density polyethylene-g-poly(acrylic acid)-co-starch/organo-montmorillonite hydrogel composite as an adsorbent for removal of Pb(Ⅱ) from aqueous solutions

The purpose of this work is to remove Pb（II） from the aqueous solution using a type of hydrogel composite. A hydrogel composite consisting of waste linear low density polyethylene, acrylic acid, starch, and organo-montmorillonite was prepared through emulsion polymerization method. Fourier transform infrared spectroscopy（FTIR）, Solid carbon nuclear magnetic resonance spectroscopy（CNMR））, silicon-29 nuclear magnetic resonance spectroscopy（Si NMR））, and X-ray diffraction spectroscope（（XRD） were applied to characterize the hydrogel composite. The hydrogel composite was then employed as an adsorbent for the removal of Pb（II） from the aqueous solution. The Pb（II）-loaded hydrogel composite was characterized using Fourier transform infrared spectroscopy（FTIR））,scanning electron microscopy（SEM））, and X-ray photoelectron spectroscopy（（XPS））. From XPS results, it was found that the carboxyl and hydroxyl groups of the hydrogel composite participated in the removal of Pb（II）. Kinetic studies indicated that the adsorption of Pb（II）followed the pseudo-second-order equation. It was also found that the Langmuir model described the adsorption isotherm better than the Freundlich isotherm. The maximum removal capacity of the hydrogel composite for Pb（II） ions was 430 mg/g. Thus, the waste linear low-density polyethylene-g-poly（acrylic acid）-co-starch/organo-montmorillonite hydrogel composite could be a promising Pb（II） adsorbent.