Leaching of tire particles and simultaneous biodegradation of leachables

The fate of organic compounds released from tire wear particle (TWP) in the aquatic environment is still poorly understood. This is especially true near sources where biotic and abiotic transformation and leaching from TWP are simultaneous and competing processes. To address this knowledge-gap an experiment was performed, allowing for biodegradation (a) during the leaching from a suspension of cryo-milled tire tread (CMTT) and (b) subsequent to leaching. Besides measuring the Dissolved Organic Carbon (DOC) content, 19 tire-related chemicals were quantified, and non-target screening was performed by LC-HRMS. The non-inoculated control experiment exhibited a DOC of up to 4 mg g-1, with up to 700 µg g-1 of 1,3-diphenylguanidine (DPG) as the most prominent compound, followed by three benzothiazoles (2-mercaptobenzothiazole (2-MBT), 2-hydroxybenzothiazole (2-OHBT) and benzothiazole-2-sulfonic acid (BTSA); 50 µg g-1 each) and 4-hydroxydiphenylamine (4-HDPA) (50 µg g-1). Biodegradation reduced the DOC by 88 % and the concentration of most organic compounds by more than 85 %. At the end of the experiment hexamethoxymethylmelamine (HMMM) was the most prominent single compounds (18 µg g-1). Non-target screening showed a more complex picture. Another 25 transformation products (TPs) of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6-PPD) and 44 TPs and derivatives related to DPG were detected in solution, of which 11 and 28 were still present after or formed by biodegradation, respectively. Of these 39 TPs and derivatives, 31 could be detected in road runoff samples. This study provides a more comprehensive picture of the leachables of tire particles that are of environmental relevance. It also outlines that derivatives of tire additives formed during tire production and use may deserve more attention as leachables. The large extent of biodegradation of tire leachables suggests that settling ponds may be a useful treatment option for road runoff.

Characterization of balsam sulfide via pyrolysis-gas chromatography-mass spectrometry/sulfur chemiluminescence detection and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Balsam sulfide, produced by the reaction of turpentine/rosin and sulfur, has been used as one of the raw materials of liquid gold to decorate ceramics and tableware with thin gold film for more than 100 years. The characterization of balsam sulfide is still insufficient because of its compositional complexity. In this study, balsam sulfide was characterized using pyrolysis-gas chromatography (Py-GC)-mass spectrometry (MS) and Py-GC with sulfur chemiluminescence detection (SCD) as well as matrix-assisted laser desorption/ionization time-of-flight MS (MALDI-TOFMS). Py-GC-MS/SCD analyses of balsam sulfide and its model samples revealed that the low molecular weight reaction products were mainly composed of compounds of one α-pinene unit reacted with 1-3 sulfur atoms. In the analysis of the high molecular weight components by MALDI-TOFMS, the products of two or three α-pinene units crosslinked by sulfur atoms were observed. It was found that dehydrogenation reaction proceeded gradually with the increase in the reaction time.

Adsorption of lead ions by activated carbon doped sodium alginate/sodium polyacrylate hydrogel beads and their in-situ recycle as sustainable photocatalysts

In this study, sodium alginate (SA), sodium polyacrylate (PAAS) and powdered activated carbon (PAC) were cross-linked by calcium ions [(Ca(II)] to form SA/PAAS/PAC (SPP) hydrogel beads. The hydrogel-lead sulfide (SPP-PbS) nanocomposites were successfully synthesized by in-situ vulcanization after the lead ions [(Pb(II)] adsorption. SPP showed an optimal swelling ratio (600% at the pH value of 5.0) and superior thermal stability (206 °C of heat-resistance index). The adsorption data of Pb(II) was compatible with the Langmuir model, and the maximum adsorption capacity of SPP was 391.65 mg/g after optimizing the mass ratio of SA to PAAS (3:1). The addition of PAC not only enhanced the adsorption capacity and stability, but also promoted photodegradation. The significant dispersive capacity of PAC and PAAS resulted in PbS nanoparticles with particle sizes of around 20 nm. SPP-PbS showed good photocatalysis and reusability. The degradation rate of RhB (200 mL, 10 mg/L) was 94% within 2 h and maintained above 80% after 5 cycles. The treatment efficiency of SPP was more than 80% in actual surface water. The results of quenching experiments and electron spin resonance (ESR) experiments revealed that the superoxide radicals (O₂^-) and holes (h⁺) were the main active species in the photocatalytic process.

Effects of the surface chemical groups of cellulose nanocrystals on the vulcanization and mechanical properties of natural rubber/cellulose nanocrystals nanocomposites

Cellulose nanocrystals (CNCs), as the promising reinforcing fillers in the rubber industry, their surface chemical groups have vital effects on the vulcanization kinetics, cross-linking densities, and mechanical properties of rubber composites. Herein, CNCs with acidic carboxyl (CCA) and alkaline amino groups (CCP) were produced by modifying the sulfonic CNCs (CCS) in environment-friendly ways. Studies found the CCS and CCA with acid groups have obvious inhibiting effects on the vulcanization of natural rubber (NR), while CCP with alkaline amino groups accelerates the vulcanization of NR. Differential scanning calorimeter, Fourier transform infrared spectroscopy, and Electron paramagnetic resonance, etc. were performed to clarify the effecting mechanisms of CNCs surface groups on NR vulcanization. It was found that NR/CCS and NR/CCA nanocomposites vulcanize through radical reactions, and the surface acidic groups of CCS and CCA, i.e., hydroxyl, sulfonate, and carboxyl groups inactivate the sulfur radicals generated during vulcanization and depress the vulcanization activity. The amino groups of the polyethyleneimine of CCP promote the ring opening of sulfur (S₈) or the breaking of polysulfide bonds connected to NR molecular chains to form sulfur anion with a strong nucleophilic ability, which leads to the cross-linking of NR/CCP reacts via ionic reaction mainly. The vulcanization rate and cross-linking density of NR/CCP are improved by the ionic reaction. And benefiting from the higher cross-linking density and the reinforcement of CCP, NR/CCP had the best physical and mechanical properties. Our work elucidates the mechanism of the surface chemical groups of CNCs affecting NR vulcanization and may provide ideas for the preparation of high-performance rubber composites reinforced by CNCs.

Porous silver microrods by plasma vulcanization activation for enhanced electrocatalytic carbon dioxide reduction

Metal electrode is considered as an ideal candidate for electrocatalytic carbon dioxide (CO₂) reduction considering its excellent chemical stability, application potential and eco-friendly properties. Optimization process such as morphological control, non-metallic doping, alloying is widely studied to improve the efficiency of metal electrodes. In this work, we successfully improved the CO₂ reduction performance of silver using a facile plasma vulcanization treatment. The obtained sulfide derived silver (Ag) porous microrods (SD-AgPMRs) are optimized from both morphology and composition aspects, and demonstrates high Faradaic efficiency and partial current density for carbon monoxide (CO) production at low potentials. The larger specific surface area of porous microrod structure and the improved adsorption energy of important intermediates in comparison with Ag foil are realized by introduction of sulfur (S) atoms after plasma vulcanization activation, as suggested by density functional theory (DFT) calculations. This work presents a novel strategy to optimize metal electrocatalysts for CO₂ reduction as well as to improve catalysis in other fields.

Cloud point extraction (CPE) combined with single particle -inductively coupled plasma-mass spectrometry (SP-ICP-MS) to analyze and characterize nano-silver sulfide in water environment

Silver Nanoparticles (Ag-NPs), an emerging type of pollutant, might occur various physical and chemical transformations, which would affect its environmental fate, transformation and biological effects. Sulfurization is the most common conversion of Ag-NPs, accompanied by the formation of nano-silver sulfide (Ag₂S-NPs). The method of Ag₂S-NPs analysis and characterization is of great significance for assessing the environmental risks of Ag. In this study, cloud point extraction (CPE) and Single Particle-Inductively Coupled Plasma-Mass Spectrometry (SP-ICP-MS) were used in combination to establish a simple and reliable analysis method to quantify Ag₂S-NPs in water, with the morphology unchanged. Non-Ag₂S-NPs were dissociated into Ag⁺ firstly, and Ag₂S-NPs and Ag⁺ were separated by CPE, followed by SP-ICP-MS analysis. The extraction rate based on particle number concentration was between (76.19 ± 0.56) % to (106.35 ± 0.00) % in environmental waters. Compared with the (76.96 ± 2.18) nm Ag₂S-NPs spiked, the particle size extracted increased slightly with (94.19 ± 2.72) nm- (97.25 ± 0.22) nm as the large-size Ag₂S-NPs originally presented in waters, instead of agglomeration. This method could be generally applicable to the analysis of Ag₂S-NPs in waters, and provide ideas for other metal sulfide nanoparticles (MS-NPs), which has certain significance.

ZnS anchored on porous N, S-codoped carbon as superior oxygen reduction reaction electrocatalysts for Al-air batteries

The development of non-precious based oxygen reduction reaction (ORR) catalysts with outstanding catalytic performance is desirable but still a grand challenge for practical Al-air battery. Herein, we report a vulcanization-assisted pyrolysis strategy for creating zeolitic imidazolate framework-derived catalysts with a N, S co-doped carbon support and highly exposed ZnS and Zn-N_x sites. The trithiocyanuric acid (TCA) is found not only to introduce S into the carbon derived from ZIF-8 and ZnS to adjust the electronic structure of carbon matrix during the pyrolysis, but also result in a shrinkage of carbon framework with a hierarchical porous structure. Such an architecture boosts abundant active sites exposed and accelerates remote mass transportation. As a result, the optimized 3.5ZnS/NSC-NaCl-900 delivers an impressive enhanced performance toward ORR in alkaline medium with a high half-wave potential of 0.905 V (vs. reversible hydrogen electrode), which is superior to most of non-precious metal-based catalysts. Density functional theory calculations unveil that the ZnS in 3.5ZnS/NSC-NaCl-900 can effectively lower the Gibbs energy barrier of crucial steps and therefore promotes the reaction kinetics. Furthermore, 3.5ZnS/NSC-NaCl-900 also displays greater power density and specific capacity than Pt/C in Al-air batteries.