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Recycling high-grade rare earth polishing powder waste (REPPW) is crucial for protecting the environment and sustainable utilization of rare earth resources. Leaching REPPW in the eco-friendly H 2 O 2 -H 2 SO 4 suffers from the lack of understanding of the leaching mechanism. Here, the leaching mechanism was investigated under the optimal leaching conditions, i.e., T = 353 K, L/S ratio = 40 mL/g, H 2 SO 4 concentration = 4 mol/L and initial H 2 O 2 concentration = 0.8 mol/L, by which leaching efficiency of Ce and La reached 99.3% and 99.1%, respectively. Furthermore, pseudo steady state kinetic analysis suggested a five-step leaching mechanism involving CeO 2 hydroxylation, H 2 O 2 -CeO 2 coordination, ≡ Ce III − H 2 O 2 deprotonation, ≡ Ce IV − H O 2 − reduction and ≡ Ce III − H O 2 ∗ protonation, which was verified by the agreement between experimental data and the proposed reaction model. This work proposes a leaching mechanism of REPPW and would help develop an effective and sustainable recycling process for rare earth secondary resources. [Display omitted] • Ce and La were effectively leached from REPPW using the H 2 O 2 -H 2 SO 4 system, resulting in leaching efficiencies of 99.3% and 99.1% for Ce and La, respectively. • A reasonable leaching cycle of CeO 2 in the H 2 O 2 -H 2 SO 4 system was verified by a pseudo steady state analysis. • A clean and efficient method for recycling rare earth solid waste resources [ABSTRACT FROM AUTHOR]

• The unexpected fracture of tube-to-tubesheet joints of a circulating oil steam generator is studied. • Caustic stress corrosion cracking is the root cause of the failure. • Proposals are given about material selection, manufacture and water quality assurance of the circulating oil steam generator. Tube-to-tubesheet joints are generally considered as one of the vulnerable part of heat exchangers, as they are sensitive to stress corrosion owing to residual stress generated during manufacture processes. As a result, it is crucial to carry out failure analysis on tube-to-tubesheet joints to ensure the safety of heat exchanger operations. The unexpected fracture of tube-to-tubesheet joints of a circulating oil steam generator in a petrochemical plant is studied. In order to find out the cause of the failure, the failed tube is investigated by visual inspection, base metal inspection and fracture morphologies observation. The results show that due to insufficient expansion of the tube, a gap is formed between the tube and tubesheet, which concentrates the alkali lye and chloride deposits, leading to the formation of caustic stress corrosion cracks in the outer wall of the failed tube before fracture, and the cracks rapidly propagate under tensile stress resulting in the failure. Finally, proposals are given about material selection, manufacture and water quality assurance of the circulating oil steam generator. [ABSTRACT FROM AUTHOR]

[Display omitted] • An Efficient and value-added flowsheet for recycling rare earth polishing powder waste is proposed. • Coordination enhanced led to high leaching ratios in mild acidic conditions. • The coordination stability constant of Ce3+-ascorbic acid was determined. • High-purity mesoporous Ce-La oxide cube was synthesized by a facile chemical precipitation method. Efficient and environmental-friendly recycling of rare earth polishing powder waste (REPPW) is imperative not only to ecological well-being but also to sustainability of critical rare earth resources. However, the low leaching efficiency of rare earth elements in mild acidic conditions and complicated synthesis procedure of high-end products hindered industrial recycling of REPPW. Herein, an ascorbic acid-H 2 SO 4 system with mild conditions, i.e., ascorbic acid concentration = 0.042 mol/dm3, H 2 SO 4 concentration = 1 mol/dm3, liquid to solid ratio = 20 cm3/g and temperature = 353 K, is proposed for leaching REPPW, in which the leaching ratios of Ce and La reached 96.79 % and 93.81 %, respectively. The coordination stability constants of Ce3+-ascorbic acid, i.e., β 1 = 106.88 and β 2 = 1013.03, were determined by pH-potentiometry, which revealed that the enhanced Ce3+ dissolution in this mild leaching system was attributed to Ce3+-ascorbic acid coordination. Subsequently, a high-purity, mesoporous Ce-La oxide cube was synthesized from the leaching solution by a facile chemical precipitation method at atmospheric pressure and temperature. The product had a composition of 78.07 wt% CeO 2 and 21.93 wt% La 2 O 3 , and its average pore diameter was 7.30 nm. Its reducibility was 1.52 times higher than the theoretical value, suggesting a high potential for catalyzing redox reactions. This work proposes an efficient and value-added process for recycling REPPW, which helps to enlighten the sustainable utilization of secondary rare earth resources. [ABSTRACT FROM AUTHOR]

The effects of the formaldehyde to phenol molar ratio (F/P) on the combustion behavior of phenolic foams were discussed. Phenolic foams have been prepared with different F/P of resole resin. FTIR, TG and SEM were used for assessment of the molecular structure, thermal stability, and cell structure of phenolic foam (PF) analysis, respectively. It was found that the higher the F/P, the more inflammables content in the PF that promoted the formation of the char layer, and the higher the LOI of PF. Although the closed cell proportion of PF decreases with the increase of F/P, the effect of the open and closed cell proportion on the LOI of PF was much lower than that of the content of inflammables when there was little difference in cell size. It is worth noting that the smoldering time and smoldering velocity of PF also increased with the increase of F/P. When F/P exceeds 2.3, a large number of open-cell structures appear in the PF, resulting in a phenomenon of smoldering to burnout. The relationship between smoldering velocity and F/P can be calculated by an Arrhenius type expression. Arrhenius-type expression calculation showed that when the F/P reached 2.3, the smoldering velocity increased sharply, reaching a maximum of 0.193 mm/s. • The factors affecting the combustion behavior of phenolic foam (PF) were revealed. • The effect of closed cell proportion on LOI of PF is lower than that of the content of inflammables. • The higher the formaldehyde to phenol molar ratio (F/P), the greater the smoldering time and velocity. • The relationship between smoldering velocity and F/P can be calculated by an Arrhenius type expression. [ABSTRACT FROM AUTHOR]

[Display omitted] • Phosphated lignocellulose nanofibrils were combined with MXene and gelatin; • The aerogel exhibited excellent fire retardancy with fire-warning performance; • Performance of electromagnetic interference shielding also achieved highly. Lightweight electromagnetic interference (EMI) shielding material with environment-friendly and high fire-safe has imperative practical significance in civil electronic devices. Herein, a distinct strategy was proposed to integrate phosphated lignocellulose nanofibrils (PLCNFs), gelatin, and MXene into a hybrid composite aerogel (PGM aerogel) with ultralight weight and high porosity. Due to the synergistic flame retardant effect of the ternary mixture, PGM aerogel exhibited excellent fire retardancy, whose dramatical changes in electronic resistance was supposed to achieve a short fire-warning signal (∼1 s). The limiting oxygen index (LOI) was as high as 32 % and the peak heat release rate (PHRR) was relatively as low as 30.1 W/g. Furthermore, the aerogel also displayed great specific EMI shielding effectiveness (SE) of SSE/t (14230 dB cm2 g−1) at 8.2 GHz. Therefore, this PGM aerogel can be a potential candidate in both EMI shielding and fire-warning fields. [ABSTRACT FROM AUTHOR]

[Display omitted] • Observed the phase transition of perovskite driven by SnO 2 under UV light. • In-situ synthesis of PSS-Pb layer at the interface of SnO 2 /perovskite. • The PSS-Pb layer was used as barrier to inhibit phase-transition of perovskite. • The PSS-Pb layer stabilize the interface and passivate interface defects. • Obtained a high open-circuit voltage of 1.19 V and an improved efficiency of 22.26% The harmonious coordination between the perovskite and the charge transport layer is the prerequisite for the high efficiency and stability of perovskite solar cells (PSCs). The excellent photoelectric and solution processable SnO 2 electron transport material opens the most commercial potential of planar PSCs. However, SnO 2 has rich surface activity and photocatalytic properties, which will deteriorate perovskite after absorbing UV light and seriously affect the stability and efficiency of PSCs. Here, the interface barrier strategy is introduced to insert an anchored-then-rinsed lead polystyrene sulfonate (ARPSS-Pb) polyionic layer between SnO 2 and perovskite via in-situ synthesis method to construct a new stable interface, which can effectively block the phase transition of perovskite driven by photocatalytic SnO 2. In addition, ARPSS-Pb also has the functions of passivating interfacial defects, relaxing interfacial stress and guiding crystallization of perovskite. PSCs based on ARPSS-Pb achieved a power conversion efficiency (PCE) of 22.26%, much higher than 19.60% of the control devices. More importantly, after 1000 h of storage under continuous humidity conditions, up to 96.32% of the initial PCE is maintained. A high open circuit voltage (V OC) as high as 1.190 V has been obtained for ARPSS-Pb based devices. To our best knowledge, this is the highest V OC achieved in the system of perovskite with 1.56 eV energy gap. [ABSTRACT FROM AUTHOR]