Relation between hydrophilic/hydrophobic characteristics of sludge extracellular polymeric substances and sludge moisture-holding capacity in hot-pressing drying.

Sludge poses a serious threat to the environmental health. Hot-pressing drying has been proven efficient in sludge treatment because of the reduced thermal contact resistance, rapid increase in sludge temperature, and high drying rate. Sludge extracellular polymeric substances (EPS) significantly influence moisture transfer. However, whether in hot-pressing or traditional thermal drying, the effect of EPS on sludge moisture-holding capacity is rarely reported. Thereby, this study investigated the relationship between hydrophilic/hydrophobic characteristics of EPS and sludge moisture-holding capacity at various drying time and mechanical compression using XAD resin fractionation. Thermodynamic analysis indicated that sludge moisture desorption isotherms, net isosteric heat of desorption, and differential entropy presented a downward trend with the increase in drying time and mechanical compression, suggesting reduced sludge moisture-holding capacity. EPS analysis showed that at the same drying time, applying 25 kPa mechanical compression increased sludge temperature by 16 % and protein content by 13.8 %. At the same sludge temperature, protein content rose by 7.3 % compared to the drying without mechanical compression. It was concluded that the fast rise in sludge temperature and the mechanical extrusion facilitated the destruction of sludge microbial flocs, accelerating the release of intracellular and EPS-bound moisture and contributing to the decrease in moisture-holding capacity. Besides, tryptophan protein-like substances were the major source of hydrophilic/hydrophobic organic matter, compared to polysaccharide and humic acid-like substances. The gradually reduced sludge moisture-holding capacity was divided into three stages. Below 67 °C, the moisture desorption was dominated by the release of intracellular moisture. Below 85 °C, the increase in protein and the enhanced exposure of hydrophobic functional groups in protein improved the hydrophobicity of EPS. Above 85 °C, protein consumption due to thermal decomposition and browning reaction facilitated the desorption of EPS-bound moisture. Hence, this study provided novel insights into the mechanism of sludge drying.

Experimental analysis on products distribution, characterization and mechanism of waste polypropylene (PP) and polyethylene terephthalate (PET) degradation in sub-/supercritical water.

Supercritical water (SCW) treatment of plastics is a clean technology in the 'waste-to-energy' path. In this work, PP and PET plastics were processed by sub-/supercritical water. The results showed that temperature was the most important factor of the PP and PET degradation. The influence of factors on the degradation of plastics follows the following order: temperature > residence time > plastic/water ratio. These factors influenced the yield of gas products by promoting or inhibiting various reactions (such as reverse water gas shift reaction, methylation reaction, and Fischer-Tropsch synthesis reaction). Besides, the composition of liquid oil was also analyzed. The main composition of the liquid oil produced by PET was benzoic acid and acetaldehyde, which were generated from the decarboxylation of terephthalic acid (TPA) and dehydration reaction of ethylene glycol (EG). The liquid oil from PP was mainly long-chain olefins, long-chain alkanes, cycloalkanes, etc., which were formed by the interaction of various methyl, alkyl, hydroxyl, and other free radicals. This study could build fundamental theories of plastic mixture treatment.

Fast pyrolysis kinetics of waste tires and its products studied by a wireless-powered thermo-balance.

Fast pyrolysis is commonly used in industrial reactors to convert waste tires into fine chemicals and fuels. However, current thermogravimetric analyzers are facing limitations that prevent the acquisition of kinetic information. To better understand the reaction kinetics, we designed a novel thermo-balance device that was capable of in-situ weight measurement during rapid heating. The results showed that the reaction rate substantially increased, with significant reductions in reaction time and apparent activation energy compared to slow pyrolysis. The change of reaction mechanism from the reaction order model to the nucleation and growth model was responsible for the increase in the degradation rate. Fast pyrolysis led to the generation of more trimers of isoprene as primary pyrolytic volatiles, which we further supported through density functional theory calculations. The findings suggested that fast pyrolysis has a higher chance of overcoming the high energy barrier to form trimers of isoprene. This comprehensive and in-depth understanding of fast pyrolysis kinetics and product distribution could reveal a more realistic process of waste pyrolysis, which benefited the industry.

The interactions between mixed waste from discarded surgical masks and face shields during the degradation in supercritical water.

The widespread use of surgical masks made of polyolefin and face shields made of polyester during pandemics contributes significantly to plastic pollution. An eco-friendly approach to process plastic waste is using supercritical water, but the reaction of mixed polyolefin and polyester in this solvent is not well understood, which hinders practical applications. This study aimed to investigate the reaction of waste surgical masks (SM) and face shields (FS) mixed in supercritical water. Results showed that the optimal treatment conditions were 400 °C and 60 min, achieving a liquid oil yield of 823.03 mg·g-1 with 25 wt% FS. The interaction between polypropylene (PP), polyethylene terephthalate (PET), and iron (Fe) in SM and FS mainly determined the production of liquid oil products such as olefins and benzoic acid. The methyl-branched structure of PP enhanced PET hydrolysis, resulting in higher production of terephthalic acid (TPA). The degradation of PP was facilitated by the acidic environment created by TPA and benzoic acid in the reaction. Moreover, the hydrolysis of PET produced carboxylic acid, which coordinated with Fe3+ to form Fe-H that catalyzed the polymerization of small olefins, contributing to higher selectivity for C9 olefins. Therefore, this study provides valuable insights into the degradation mechanism of mixed PPE waste in supercritical water and guidance for industrial treatment.

Adsorption performance and mechanism of cationic and anionic dyes by KOH activated biochar derived from medical waste pyrolysis.

The massive generation of medical waste (MW) results in a series of environmental, social, and ecological problems. Pyrolysis is one such approach that has attracted more attention because of the production of value-added products with lesser environmental risk. In this study, the activated biochar (ABC600) was obtained from MW pyrolysis and activated with KOH. The adsorption mechanism of activated biochar on cationic (methylene blue) and anionic (reactive yellow) dyes were studied. The physicochemical characterization of biochar showed that increasing pyrolysis temperature and KOH activation resulted in increased surface area, a rough surface with a clear porous structure, and sufficient functional groups. MB and RYD-145 adsorption on ABC600 was more consistent with Langmuir isotherm (R2 ≥ 0.996) and pseudo-second-order kinetics (R2 ≥ 0.998), indicating chemisorption with monolayer characteristics. The Langmuir model fitting demonstrated that MB and RYD-145 had maximum uptake capacities of 922.2 and 343.4 mg⋅g-1. The thermodynamics study of both dyes showed a positive change in enthalpy (ΔH°) and entropy (ΔS°), revealing the endothermic adsorption behavior and randomness in dye molecule arrangement on activated-biochar/solution surface. The activated biochar has excellent adsorption potential for cationic and anionic dyes; hence, it can be considered an economical and efficient adsorbent.

Experimental analysis on products distribution and characterization of medical waste pyrolysis with a focus on liquid yield quantity and quality.

The massive generation of medical waste (MW) poses a serious risk to the natural environment and human health. The pyrolysis technique is proposed as a potential treatment for MW to tackle the associated environmental issues and produce value-added products. In this work, medical waste pyrolysis has been conducted at various temperatures using a fixed bed reactor with a 20 °C·min-1 heating rate and nitrogen was used as a career gas with a flow rate of 100 ml·min-1. In addition, the effect of temperature on products yield and chemical composition of MW pyrolysis have been investigated. The maximum yield of 57.1% for liquid oil was observed from the mixed MW pyrolysis at 500 °C. The gas and char yield were found between 26.5-37.3% and 24.2-12.4%, respectively, for the pyrolysis temperature of 450 °C to 600 °C. According to GC analysis, the concentration of the main gaseous products such as CH4, H2, and C2H4 was increased with increasing temperature, while CO and CO2 experienced a decreasing trend. The results of GC-MS analysis revealed that the main components of MW pyrolysis oil were aromatic hydrocarbons, cyclic hydrocarbons, aliphatic hydrocarbons, alcohol, carboxylic acids, and their derivatives. The aromatic and cyclic hydrocarbons content increased up to 38.2% at a pyrolysis temperature of 600 °C. As pyrolysis oil tends to have more long-chain hydrocarbons therefore carbon distributions from C7 to C35 were observed. The ultimate analysis of oil and char revealed that the increased temperature enhanced the carbon content up to 78.6% and 68.0%, respectively. Furthermore, the higher heat values of 41.8, 24.4, and 52.7 MJ·kg-1 were reported for oil, char, and gas, respectively.

Effect of in-situ torrefaction and densification on the properties of pellets from rice husk and rice straw.

The research on preparing high-quality pellets by combining torrefaction and densification of biomass has received widespread attention. This paper investigated the influence of torrefaction temperature on biomass and evaluated the quality of three kinds of pellets (raw pellets, ex-situ torrefied densified pellets and in-situ torrefied densified pellets). When the torrefaction temperature was raised to 300 °C, the energy yield of rice straw (RS) and rice husk (RH) quickly decreased to 71.08% and 77.62%, and the cellulose was decomposed significantly. The results proved that 250 °C was an optimum temperature for RS and RH torrefaction. The densities of RS and RH in-situ torrefied densified pellets were 1236.84 kg/m3 and 1277.50 kg/m3 under 150 MPa, respectively. The density, Meyer hardness, hydrophobicity, and mechanical specific energy consumption of the pellet increased with the increase of molding pressure. The in-situ pellets had higher Meyer hardness, hydrophobicity, and lower mechanical specific energy consumption under the same molding pressure than raw pellets and ex-situ torrefied densified pellets. In addition, the bonding mechanism was studied by using scanning electron microscopy and ultraviolet auto-fluorescence. In-situ torrefaction and densification facilitated the formation of self-locking and the migration of lignin between particles. Compared with RH pellets, RS pellets had higher quality due to the higher hemicellulose content, which was necessary for forming stable hydrogen bonds.

Hydrogen-rich syngas from wet municipal solid waste gasification using Ni/Waste marble powder catalyst promoted by transition metals.

Gasification of wet municipal solid waste (MSW) coupled with in-situ CO2 capture is an attractive option for MSW disposal, allowing chemical and energy recovery. In this study, the Ni-CaO based catalysts were prepared with waste marble powder (WMP) as an alternative to CaO and promoted by different transition metals (i.e., Fe, Cu, Co and Zn). The bimetallic catalysts were prepared by the impregnation method and characterized by different analytical techniques. The catalyst performance for wet MSW gasification was evaluated in a fixed-bed reactor at optimized conditions (850 °C and 50% moisture content of MSW). The results revealed that the addition of Ni-WMP catalyst greatly enhanced the dry gas yield (DGY), H2 yield, carbon conversion efficiency (CCE) and reduced the tar content from 0.73 to 1.16 N.m3/kg, 212 to 509 mL/g, 61.70% to 76.40% and 9.11 to 3.9 wt%, respectively, compared to without catalyst. In contrast to the Ni-WMP catalyst, the transition metal promoted catalysts showed higher catalytic activity towards H2 yield (549-629 mL/g), DGY (1.19-1.30 N.m3/kg), and lower tar content (3.45-2.93 wt%). The results revealed that Co promoted bimetallic catalyst performed better than Fe, Cu and Zn promoted catalysts. The tar content produced was also analyzed via GC-MS (gas chromatography-mass spectrometry) to understand the effect of different catalysts on tar composition. According to experimental results, the bimetallic promoted catalysts can be ranked as Ni-Co-WMP > Ni-Cu-WMP > Ni-Fe-WMP > Ni-Zn-WMP based on H2 yield and tar removal.

Enhancement of conductive drying of sewage sludge with mechanical compression: Drying kinetics, and interfacial heat transfer behavior.

Improving sludge drying efficiency is of tremendous importance for public health, subsequent treatment, and comprehensive utilization. The interfacial thermal resistance between sludge and hot wall greatly limits the conductive drying performance. This study employed mechanical compression to decrease the interfacial thermal resistance. The drying kinetics and interfacial heat transfer behavior were investigated at mechanical loads of 25 to 200 kPa, temperatures of 120 to 210 °C, and sludge thicknesses of 1.0 to 3.0 mm, and were compared to those in the conventional drying process without mechanical load. The increase of temperature and mechanical load and the decrease of thickness improved drying rates. The drying experienced one warm-up period and two falling rate periods. The breakthrough of interfacial vapor film was responsible for the rapid rise in drying rates initially. At the thickness of 3.0 mm, 210 °C, and 100 kPa, the effective moisture diffusivity was increased by 2.5 times, and the apparent activation energy was reduced by 34% compared to the traditional process in the first falling rate period, implying that mechanical compression facilitated moisture migration and bound water desorption. The effective moisture diffusivity in the first falling rate period was increased by 35% compared to the diffusivity in the second falling rate period because of the pressure-driven flow. The decrease in drying rates was due to the transformation from the pressure-driven flow to vapor diffusion-limited flow in the first falling rate period. Additionally, this study provided essential information on developing a new sludge treatment method and establishing the drying model.

Mechanical compression assisted conductive drying of thin-film dewatered sewage sludge: Process performance, heat and mass transfer behavior.

The improvement in heat transfer efficiency between the hot wall and sewage sludge was a critical issue to enhance the conductive drying performance. The drying behavior of thin-film dewatered sewage sludge was investigated based on a conductive dryer assisted with mechanical compression at hot wall temperatures of 120-210 °C. The heat and mass transfer behavior of the sludge in the conductive drying process alone was compared to those in the mechanical compression assisted conductive drying process at three external mechanical loads of 25, 100, and 200 kPa. The average drying rates with mechanical compression were higher than those without mechanical load and were enhanced with the increase of mechanical loads at 210 °C. The extrusion of interfacial vapor film and the reduction of sludge surface roughness was responsible for the enhanced interfacial heat transfer efficiency under mechanical compression. The effective moisture diffusivity, mass transfer coefficient, and effective thermal conductivity were enhanced by mechanical compression. The improved moisture transfer inside sludge and on the open surface, and the decreased heat transfer resistance of sludge was due to the generated pressure-driven flow and the reduced gas cavities in sludge, resulting in the higher drying rates. Additionally, this finding provided reference data for developing a new sludge drying method.

Influencing mechanism of zinc mineral contamination on pyrolysis kinetic and product characteristics of corn biomass.

The metal mineral has a complex influence on the thermal decomposition of biomass due to the sophisticated structure of biomass and parallel reactions. Therefore, the influencing mechanisms of metal minerals on biomass decomposition kinetic expressions needed to be thoroughly investigated. In this study, the decomposition of the three major components of biomass was considered separately. The iso-conversional method and integral master-plots method based on thermogravimetry were firstly introduced to explore the kinetic model changes after the introduction of zinc mineral. The thermogravimetric results showed that the presence of zinc mineral had discrepant influences on different biomass components, demoting the fragmentation of hemicellulose while promoting cellulose degradation. In the kinetic analysis, the presence of zinc mineral, the activation energy of three pseudo-components (91.90, 184.64 and 210.91 kJ mol-1) increased to 178.84, 299.05, and 359.45 kJ mol-1, respectively. The kinetic models were altered from 2.0-order reaction (F2.0) for hemicellulose, random nucleation (A1.8) for cellulose, and 2.3-order reaction (F2.3) for lignin to F2.8, F3.0, and F3.2, respectively. This indicated that the zinc mineral was beneficial to the occurrence of multimolecular repolymerization of the primary degradation products. In products analysis, the increment of biochar yields and the C4-C5 products of cellulose (especially furfural) in metal-polluted biomass pyrolysis were detected, which confirmed the simulated reaction mechanisms. The obtained results are expected to provide a mechanism reference to practical applications of metal-contaminated biomass.

The Determination of Pore Shape and Interfacial Barrier of Entry for Light Gases Transport in Amorphous TEOS-Derived Silica: A Finite Element Method.

The interfacial barrier of entry for light gas transport in a nanopore was a crucial factor to determine the separation efficiency in membrane technologies. To examine this effect, amorphous silica was prepared by sol-gel process, and its characterization results revealed that the commonly used cylindrical pore shape failed to represent the adsorption behavior of gases, but instead the pore shape had to be represented by a slit pore model. A finite element method (FEM) was developed to analyze the interfacial resistance by integrating a Lennard-Jones (LJ) potential over the layer area. It was found that the strong repulsion/attraction at the pore interface could be paired with the motion energy of guest molecules to predict the ideal selectivity between gases, thereby providing a solution to preliminarily screen the separation performance among a host of membrane candidates.

Doping strategy, properties and application of heteroatom-doped ordered mesoporous carbon.

To date, tremendous achievements have been made to produce ordered mesoporous carbon (OMC) with well-designed and controllable porous structure for catalysis, energy storage and conversion. However, OMC as electrode material suffers from poor hydrophilicity and weak electrical conductivity. Numerous attempts and much research interest have been devoted to dope different heteroatoms in OMC as the structure defects to enhance its performance, such as nitrogen, phosphorus, sulphur, boron, and multi heteroatoms. Unfortunately, the "how-why-what" question for the heteroatom-doped OMC has not been summarized in any published reports. Therefore, this review focuses on the functionalization strategies of heteroatoms in OMC and the corresponding process characteristics, including in situ method, post treatment method, and chemical vapor deposition. The fundamentally influencing mechanisms of various heteroatoms in electrochemical property and porous structure are summarized in detail. Furthermore, this review provides an updated summary about the applications of different heteroatom-doped OMC in supercapacitor, electrocatalysis, and ion battery during the last decade. Finally, the future challenges and research strategies for heteroatom-doped OMC are also proposed.

Integrated thermal behavior and compounds transition mechanism of municipal solid waste incineration fly ash during thermal treatment process.

Thermal behavior of municipal solid waste incineration (MSWI) fly ash is extremely complicated due to the simultaneously occurred reactive processes and the products with different chemical compositions, therefore, the investigation of chemical compounds transition behavior and mechanism during the integrated thermal process is of great significance. In this study, the macro-thermal treatment of fly ash and thermo-gravimetric analysis via non-isothermal methods were carried out and Málek method was firstly introduced to explore the mechanism of multi-step reaction for fly ash. The mineral transition results suggested that the halite, sylvite in the raw fly ash transformed to more complex crystals in treated samples, such as chlorellestadite, polyhalite and enstatite during the thermal process. And the heavy metals leaching concentration decreased with the temperature increased from 300 °C to 1200 °C, and the leaching values were lower than the standard limitation after thermal treatment. In addition, three major steps of fly ash reactions (300-380 °C, 650-750 °C and 890-1130 °C) during the thermal process were observed and expressed by first order reaction for the first step, three-dimensional diffusion for the second step and three dimensions of limiting surface reaction between both phases for the third step, respectively. The kinetic study revealed that the mineral transition process was in well accordance with the simulated reaction mechanism during the thermal treatment. The obtained results are expected to provide the research basis for studying detailed thermal characteristics and reaction mechanism during the thermal treatment of MSWI fly ash.

Synergistic effects of anionic surfactants on adsorption of norfloxacin by magnetic biochar derived from furfural residue.

Norfloxacin (NOR) is a persistent organic pollutant and can be effectively removed from effluent by adsorption of biochar. However, the presence of other emerging contaminants, such as surfactants, will potentially alter adsorption performance of norfloxacin by biochar and the molecular-scale mechanisms of the interaction between surfactants and biochar remain poorly understood. In this study, adsorption of norfloxacin on magnetic biochar prepared with iron-containing furfural residue (FRMB) in the presence or absence of anionic surfactants was investigated. The adsorption of NOR was significantly affected by the initial pH and anionic surfactants-sodium dodecyl sulfate (SDS) and sodium dodecyl benzene sulfonate (SDBS). In the presence of SDS and SDBS, the maximum sorption capacities of NOR were 2.33 and 1.97 times higher than that in the absence of surfactants, reached to 698.6 mg g-1 and 589.9 mg g-1, respectively. The optimal pH condition which was 4 indicated that electrostatic adsorption played a decisive role in the adsorption process after introduction of SDS/SDBS. The adsorption data were fitted well by the Elovich model and Freundlich model at the optimal conditions in which both SDS and SDBS were hemimicelle (0.8 mM SDS or 0.4 mM SDBS), indicating surface heterogeneity of FRMB and the adsorption mechanism was related to the assembly of surfactants on biochar. FTIR results showed that FRMB and SDS/SDBS interacted through hydrophobic action, and more complex or aggregates were formed between the NOR and biochar/SDS/SDBS. This work highlights the synergistic enhancement effects of tested surfactants on the removal of NOR by magnetic biochar from aqueous systems.

Kinetic analysis for cyclic CO2 capture using lithium orthosilicate sorbents derived from different silicon precursors.

A series of Li4SiO4 was synthesized using LiNO3 and six different silicon precursors. The precipitated-silica-derived Li4SiO4 presented the highest CO2 capacity in a 10 h sorption test, and ZSM-5-derived Li4SiO4 demonstrated the most rapid CO2 sorption. The CO2 sorption kinetics predominantly followed the nucleation mode and could be accurately described by the Avrami-Erofeev model. The Avrami-Erofeev model provided an in-depth analysis of correlation between sorption performance and material properties. Both the nucleation speed and nucleation dimensionality affected the overall sorption kinetics. The kinetics and pore-size distribution suggest that the sorption kinetics was dependent on the quantity of ∼4 nm-pores which favors nucleation dimensionality. For the cyclic tests, the precipitated-silica-derived sample presented the poorest performance with the capacity decreasing from 31.33 wt% at the 1st cycle to only 11.52 wt% at the 30th cycle. However, the sample made from fumed silica displayed an opposite trend with the capacity increasing from 19.90 wt% at the 1st cycle to 34.23 wt% at the 30th cycle. The radically distinct behaviour of samples during cycles was on account of the alternation of sorption kinetics. The decrease in ∼4 nm-pores after cycles was responsible for the decrease of nucleation dimensionality for the precipitated-silica-derived sample. The rearrangement during cycles could enrich the pores of ∼4 nm for the fumed silica-derived sample, which improved the nucleation growth, thus enhancing the kinetics with cycles.

Enhanced Hydrogen Production from Sawdust Decomposition Using Hybrid-Functional Ni-CaO-Ca2SiO4 Materials.

A hybrid-functional material consisting of Ni as catalyst, CaO as CO2 sorbent, and Ca2SiO4 as polymorphic "active" spacer was synthesized by freeze-drying a mixed solution containing Ni, Ca and Si precursors, respectively, to be deployed during sawdust decomposition that generated gases mainly containing H2, CO, CO2 and CH4. The catalytic activity showed a positive correlation to the Ni loading, but at the expense of lower porosity and surface area with Ni loading beyond 20 wt %, indicating an optimal Ni loading of 20 wt % for Ni-CaO-Ca2SiO4 hybrid-functional materials, which enables ∼626 mL H2 (room temperature, 1 atm) produced from each gram of sawdust, with H2 purity in the product gas up to 68 vol %. This performance was superior over a conventional supported catalyst Ni-Ca2SiO4 that produced 443 mL H2 g-sawdust-1 under the same operating condition with a purity of ∼61 vol %. Although the Ni-CaO bifunctional material in its fresh form generated a bit more H2 (∼689 mL H2 g-sawdust-1), its cyclic performance decayed dramatically, resulting in H2 yield reduced by 62% and purity dropped from 73 to 49 vol % after 15 cycles. The "active" Ca2SiO4 spacer offers porosity and mechanical strength to the Ni-CaO-Ca2SiO4 hybrid-functional material, corresponding to its minor loss in reactivity over cycles (H2 yield reduced by only 7% and H2 purity dropped from 68 to 64 vol % after 15 cycles).

Spray-Dried Sodium Zirconate: A Rapid Absorption Powder for CO2 Capture with Enhanced Cyclic Stability.

Improved powders for capturing CO2 at high temperatures are required for H2 production using sorption-enhanced steam reforming. Here, we examine the relationship between particle structure and carbonation rate for two types of Na2 ZrO3 powders. Hollow spray-dried microgranules with a wall thickness of 100-300 nm corresponding to the dimensions of the primary acetate-derived particles gave about 75 wt % theoretical CO2 conversion after a process-relevant 5 min exposure to 15 vol % CO2 . A conventional powder prepared by solid-state reaction carbonated more slowly, achieving only 50 % conversion owing to a greater proportion of the reaction requiring bulk diffusion through the densely agglomerated particles. The hollow granular structure of the spray-dried powder was retained postcarbonation but chemical segregation resulted in islands of an amorphous Na-rich phase (Na2 CO3 ) within a crystalline ZrO2 particle matrix. Despite this phase separation, the reverse reaction to re-form Na2 ZrO3 could be achieved by heating each powder to 900 °C in N2 (no dwell time). This resulted in a very stable multicycle performance in 40 cycle tests using thermogravimetric analysis for both powders. Kinetic analysis of thermogravimetric data showed the carbonation process fits an Avrami-Erofeyev 2 D nucleation and nuclei growth model, consistent with microstructural evidence of a surface-driven transformation. Thus, we demonstrate that spray drying is a viable processing route to enhance the carbon capture performance of Na2 ZrO3 powder.