Exploring into a light-avoided environment: Mechanical-thermal coupled conditions responsible for the aging behavior of plastic waste in landfills.

Plastics in landfills undergo a unique micronization process due to multi-factor and light-avoided conditions, but their aging process in such a typical environment remains unexplored. This study investigated the aging behavior of polyethylene plastics, representative of landfills, under simulated dynamic mechanical forces and high temperature-two prevalent environmental factors in landfills. The study explored the individual and combined contributions of these factors to the aging process. Results indicated that high temperature played a primary role in aging plastics by depolymerization and degradation through ·OH production, while mechanical forces contributed mainly to surface structure breakdown. The combined effect leads to more serious surface damage, creating holes, cracks, and scratches that provide access for free radical reactions to plastic bulk, thereby accelerating the aging and micronization process. The resulting microplastics were found to be 14.25 ± 0.53 µg L-1. Aged plastics exhibit a rapid aging rate of depolymerization and oxidation compared to virgin plastics due to their weak properties, suggesting a higher potential risk of microplastic generation. This study fills a knowledge gap regarding the aging behavior of plastics under complex and light-avoided landfill conditions, emphasizing the need for increased attention to the evolution process of microplastics from aged plastic waste in landfills.

Identifying the fate of nitrogenous species during sewage sludge pyrolysis via in-situ tracing of protein-sludge inherent components interactions.

The effect of interactions between different components in sewage sludge on the thermochemical transformation of nitrogenous species is usually neglected, which is important to explain the generation mechanism of some key nitrogenous by-products. Here, we investigated the distribution, form, and chemical properties of the products from sludge-extracted protein (PR) under different pyrolysis scenarios using several in-situ probe techniques, to elucidate the critical role of typical sludge organics/inorganics on the evolution of nitrogenous intermediates and by-products. The results suggested that Ca/Fe/Si/Al-containing inorganics significantly affected the pyrolytic behavior of PR and the thermal transformation of nitrogenous species, while sludge organics, including humic acids and polysaccharides, had limited effects on the temperature-dependent evolution of nitrogenous species in PR. Among them, calcium oxide catalyzed the ring-opening reaction of heterocyclic-N with aromatic-like structures, resulting in a 21.1 %-68.8 % reduction in nitrogen fixation efficiency in the char. At lower temperatures (350-450 °C), calcium oxide caused more nitrogen to be transferred to the gas/tar phases in the form of NH3 and heterocyclic-N, and it also enhanced the conversion of nitrile-N → HCN → NO at temperatures above 450 °C. In contrast, polyferric salts inhibited the devolatilization of mono-heterocyclic-N and enhanced the thermal stability of poly-heterocyclic-N, resulting in a maximum increase of 18.5 mg·g-1 of nitrogen content in the char, while reducing the release of NH3 and HCN by 71.1 % and 32.0 %. This work elucidated the interaction between PR and inherent components in sludge, providing key information for the control of nitrogenous volatiles and NOx.

Carbon sequestration for high-quality sludge-based carbon preparation via K/Na bi-molten salts pyrolysis.

Pyrolysis carbonization of sewage sludge is employed to achieve carbon sequestration and access carbon resources, while the quality of the obtained sludge-based carbon (SBC) is poor due to high ash contents and volatile organic matter. Here, carbonization in KOH/Na2CO3 (K/Na) bi-molten salts was developed for SBC preparation, improvement of carbon exploitation from biomass, and to reduce the contents of ash and volatile organic matter. The results showed that the surface area and pore volume of SBC under optimized conditions reached 1631 m2 g-1 and 1.312 cm3 g-1 at 700 °C, respectively, with a K/Na bi-molten salts/sludge ratio of 2:1 (K:Na = 5:5). Moreover, over fivefold the higher surface area and 43.61% amount of carbon element could be obtained, with a decrease in the mass loss rate for sludge pyrolysis of 25%. The mechanism behind the higher surface area of the SBC was identified and divided into three stages: intense dehydration and dehydrogenation caused by molten salt-enhanced polycondensation of protein and polysaccharide (200-400 °C), strongly reduced carbon-oxygen structure after deoxygenation reactions (400-600 °C), aromatization and cyclization of long-chain fatty acids triggered by deamidation of tar catalyzed by molten salts (600-900 °C). Eventually, 14.63% carbon was sequestered for the high-surface-area SBC prepared by K/Na bi-molten salts system.

Solar-Driven Evaporators with Thin-Film-Composite Architecture Inspired by Plant Roots for Treating Concentrated Nano-/Submicrometer Emulsions.

Oil/water separation by porous materials has received growing interest over the past years since the ever-increasing oily wastewater discharges seriously threaten our living environment. Purification of nano-sized and concentrated emulsions remains a big challenge because of the sharp flux decline by blocking the pores and fouling the surfaces of those porous materials. Herein, we propose a solar-driven evaporator possessing thin-film-composite architecture to deal with these two bottlenecks. Inspired by plant roots, our evaporator composes of a large-pore sponge wrapped by a thin hydrogel film, which is constructed by the contra-diffusion and cross-linking of alginate and calcium ions at the sponge surface. The dense superoleophobic hydrogel layer serves as a selective barrier that prevents oil emulsions but allows water permeation, while the inner sponge with large pores facilitates water transport within the evaporator, ensuring sufficient water supply for evaporation. By splitting the single evaporator into an array, the evaporator performs a high evaporation rate of ∼3.10 kg·m-2·h-1 and oil removal efficiency above 99.9% for a variety of oil emulsions. Moreover, it displays a negligible decline in the evaporation rate when treating concentrated emulsions for 8 h.

An emission-free controlled potassium pyrosulfate roasting-assisted leaching process for selective lithium recycling from spent Li-ion batteries.

Recycling critical metals from spent Li-ion batteries (LIBs) is important for the overall sustainability of future batteries. This study reports an improved sulfation roasting technology to efficiently recycle Li and Co from spent LiCoO2 LIBs using potassium pyrosulfate as sulfurizing reagent. By sulfation roasting, LiCoO2 was converted into water-soluble lithium potassium sulfate and water-insoluble cobalt oxide. Under optimal conditions, 98.51% Li was leached in water, with a selectivity of 99.86%. More importantly, sulfur can be recirculated thoroughly, and the sulfur atomic efficiency can be significantly enhanced by controlling the amount of potassium pyrosulfate. Li ions from the water leaching process were recovered by chemical precipitation. Furthermore, application of this technology to other spent LIBs, such as LiMn2O4 and LiNi0.5Co0.2Mn0.3O2, verified its effectiveness for selective recovery Li. These findings can provide some inspiration for high efficiency and environmentally friendly recovery metal from spent LIBs.

Suspended Membrane Evaporators Integrating Environmental and Solar Evaporation for Oily Wastewater Purification.

Solar-driven evaporation is promising in oily wastewater treatment, in particular for emulsions, but conventional evaporators suffer from pore blocking by residual oil or contamination by volatile oil compounds in the condensed water. In the current research, we develop a suspended membrane evaporator integrating solar evaporation with oil-in-water emulsion separation. The heating and evaporating interface is separated from the rejecting interface to avoid oil escape and improve heat management. A temperature gradient forms on the membrane surface that can promote evaporation performance by combining both solar and environmental evaporation. Such an evaporator achieves a maximum evaporation rate of 1.645 kg/(m2·h) as well as an apparent evaporation efficiency of 111.9%. Moreover, the superhydrophilic and superoleophobic membrane shows excellent oil repellence and emulsion rejection, which can achieve an oil removal efficiency above 98.8% in oil-in-water emulsion separation, and high evaporation rate recovery in cycling tests. A scaled-up membrane evaporator array produces ∼8 kg/(m2·d) of clean water from oily wastewater in outdoor experiments, further demonstrating the strong purification performance of this evaporator in oily wastewater treatment.

Ultrasonic power combined with seed materials for recovery of phosphorus from swine wastewater via struvite crystallization process.

Recovering P via struvite crystallization is an effective way to utilize the resources in swine wastewater. At present, the main challenges of traditional struvite crystallization process are the long reaction time and insufficient removal efficiency. In this study, a novel method to promote struvite crystallization process through ultrasound (US) combined with seed materials is proposed to overcome these defects. We systematically study the effects of US, seed materials, and ultrasonic power on nutrient recovery. The experimental results show that under the conditions of pH 9.5 and MgCl2:P molar ratio1.4:1, the addition of 2 g/L pre-synthesized struvite as the seed materials can increase the P removal rate to 91.56%, whereas, the addition of 80 W ultrasonic power for 15 min can make the P removal rate reach 94.18%. Meanwhile, the combination of US and struvite seed crystals can achieve a maximum P removal efficiency value of 97.66% in which 10 min for the reaction time is enough. The products are characterized using XRD, SEM, and FTIR to determine the phosphorus removal mechanism of ultrasonic power combined with seed induction. The shearing effect of US is found beneficial to affect the surface morphology of the seed crystals, which provides more nucleation sites to enhance crystal nucleation and growth. The removal efficiency comparison reveals that this combined technology performs an excellent removal effect.

Brushable Lubricant-Infused Porous Coating with Enhanced Stability by One-Step Phase Separation.

Slippery lubricant-infused porous surface (SLIPS) is a promising solution to undesired adhesion. Unfortunately, the complicated fabrication process and limited coating area block its practical applications. Herein, we report a one-step strategy to fabricate polypropylene-based SLIPS coatings through thermally induced phase separation, in which the lubricant is in situ infiltrated within a polymer network formed during cooling. The solid-liquid-phase separation process was monitored by an in situ hot-stage microscope. Such coating performs outstanding self-cleaning, anti-corrosion, and anti-bacterial performance, as well as enhanced stability of the lubricant layer because the lubricant is well adapted in the structure.

Ion exchange induced removal of Pb(ii) by MOF-derived magnetic inorganic sorbents.

Nanoporous adsorbents of ZnO/ZnFe2O4/C were synthesized by using a metal organic framework (Fe(III)-modified MOF-5) as both the precursor and the self-sacrificing template. The adsorption properties of ZnO/ZnFe2O4/C toward Pb(ii) ions were investigated, including the pH effect, adsorption equilibrium and adsorption kinetics. The adsorption isotherms and kinetics were well described by using the Langmuir isotherm model and pseudo-second-order model, respectively. The MOF-derived inorganic adsorbents exhibited high absorption performance with a maximum adsorption capacity of 344.83 mg g(-1). X-ray powder diffraction and high-resolution X-ray photoelectron spectroscopy suggest that Zn(ii) was substituted by a significant portion of Pb(ii) on the surface of ZnO nanocrystals. Microscopic observations also demonstrate the effect of Pb(ii) ions on ZnO crystals as reflected by the considerably reduced average particle size and defective outer layer. Quantitative measurement of the released Zn(ii) ions and the adsorbed Pb(ii) ions indicated a nearly linear relationship (R(2) = 0.977). Moreover, Pb-containing ZnO/ZnFe2O4/C adsorbents are strongly magnetic allowing their separation from the water environment by an external magnet.

Sol-hydrothermal synthesis of inorganic-framework molecularly imprinted TiO2/SiO2 nanocomposite and its preferential photocatalytic degradation towards target contaminant.

Inorganic-framework molecularly imprinted TiO2/SiO2 nanocomposite (MIP-TiO2/SiO2) was successfully prepared by sol-hydrothermal method using 4-nitrophenol as template. The morphology, structure, optical property, zeta-potential and photocurrent of MIP-TiO2/SiO2 were characterized. The adsorption performance and photocatalytic selectivity were also studied. MIP-TiO2/SiO2 shows higher adsorption capacity and selectivity than the non-imprinted TiO2/SiO2 (NIP-TiO2/SiO2). Kinetics results show that the adsorption equilibrium of 4-nitrophenol on MIP-TiO2/SiO2 is established within 20 min, and the adsorption process obeys the pseudo-second-order model. Moreover, MIP-TiO2/SiO2 can completely degrade 4-nitrophenol within 30 min, while NIP-TiO2/SiO2 takes 110 min. It was found that the MIP-TiO2/SiO2 photocatalyst shows molecular recognition ability, leading to selective adsorption and molecular recognitive photocatalytic degradation of 4-nitrophenol. Furthermore, because of its inorganic framework, MIP-TiO2/SiO2 shows excellent reusability.

Direct removal of aqueous As(III) and As(V) by amorphous titanium dioxide nanotube arrays.

Amorphous titanium dioxide nanotube arrays (TiO2 NTs) were prepared by a simple anodization process without subsequent calcination at high temperature, and the effectiveness of amorphous TiO2 NTs as adsorbents in removing arsenite (As(III)) and arsenate (As(V)) was investigated. The TiO2 NTs were not only effective for arsenic removal without a pre-oxidation of As(III) to As(V) and/or adjusting the pH value of water before the adsorption process, but also can be separated and recovered easily from the solution. The adsorption kinetics and adsorption capacity of the amorphous TiO2 NTs for As(III) and As(V) were studied separately by batch experiments. The apparent values for Langmuir monolayer sorption capacities were 28.9 mg/g for As(III) and 24.7 mg/g for As(V) at pH 7. Kinetics studies indicated that the adsorption process on TiO2 NTs followed a pseudo-second-order kinetics model. Arsenic adsorption of TiO2 NTs remains stable over a broad pH range. Moreover, the TiO2 NTs have excellent stability and regeneration, and they can be used repeatedly at least five times.

Visible-light photocatalytic degradation performances and thermal stability due to the synergetic effect of TiO2 with conductive copolymers of polyaniline and polypyrrole.

Conductive polypyrrole-polyaniline/TiO2 nanocomposites (PPy-PANI/TiO2) were prepared by in situ oxidative copolymerization of pyrrole and aniline monomers in the presence of TiO2. For comparison studies, polypyrrole/TiO2 (PPy/TiO2) and polyaniline/TiO2 (PANI/TiO2) were also prepared. The samples were characterized by X-ray diffraction, transmission electron microscopy, UV-vis diffuse reflectance spectroscopy, zeta potential analysis, Fourier transform infrared spectroscopy, thermogravimetric analysis and photocurrent tests. In contrast to PPy/TiO2 and PANI/TiO2, PPy-PANI/TiO2 exhibits obvious absorption in the visible-light range, and is much superior to PPy/TiO2 and PANI/TiO2 in thermal stability. It is found that PPy-PANI/TiO2 performs well in the visible-light photocatalytic degradation of 4-nitrophenol. The optimized pyrrole : aniline : TiO2 molar ratio for best performance is 0.75 : 0.25 : 100. The efficacy of PPy-PANI/TiO2 is attributed to its conductivity, conjugated structure, as well as to the synergy amidst polypyrrole, polyaniline and TiO2.