Distribution characteristics and migration pathways of metals during hydrothermal liquefaction of municipal sewage sludge in the presence of various catalysts.

A series of hydrothermal liquefaction (HTL) experiments with two different samples of municipal sewage sludge (MSS) were conducted at 350 °C for 30 min residence time in a high pressure batch reactor. The main aim of the study was to explore the distribution and migration pathways of a broad range of metals and metalloids in the HTL products (bio-oil, char and aqueous phase) obtained in the presence of various homogeneous and heterogeneous catalysts (Na2CO3, Li2CO3, K2CO3, Ba(OH)2, Fe2O3, CeO2, NiMo/MoO3, MoS2, Ni/NiO, SnO2, FeS). The elements under study included 16 environmentally significant metals and metalloids (As, B, Ba, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Sb, Se, Sn, Zn and Hg). The study showed that the quantitative migration of the tested metals and metalloids to the particular HTL products, relative to their initial content in the raw sludge, is different for the individual elements. Most metals exhibited a particularly strong affinity to the solid fraction (biochar). In the obtained HTL bio-oils, all tested elements were identified, except of Cd. It was also found that B and As have high affinity to the aqueous phase. A direct effect of catalysts on the contents of some elements in the products was also proved by the study, e.g. increased concentration of Cr in the biochar when Fe2O3 was used as a process catalyst. Due to the wide scope of the tested elements and broad range of catalyst used, the results obtained represent a unique and comprehensive set of environmental data compared to similar HTL studies previously conducted for MSS.

Predicting co-liquefaction bio-oil of sewage sludge and algal biomass via machine learning with experimental optimization: Focus on yield, nitrogen content, and energy recovery rate.

Machine learning (ML), a powerful artificial intelligence tool, can effectively assist and guide the production of bio-oil from hydrothermal liquefaction (HTL) of wet biomass. However, for hydrothermal co-liquefaction (co-HTL), there is a considerable lack of application of experimentally verified ML. In this work, two representative wet biomasses, sewage sludge and algal biomass, were selected for co-HTL. The Gradient Boosting Regression (GBR) and Random Forest (RF) algorithms were employed for regression and feature analyses on yield (Yield_oil, %), nitrogen content (N_oil, %), and energy recovery rate (ER_oil, %) of bio-oil. The single-task results revealed that temperature (T, °C) was the most significant factor. Yield_oil and ER_oil reached their maximum values around 350 °C, while that of N_oil was around 280 °C. The multi-task results indicated that the GBR-ML model of the dataset#4 (n_estimators = 40, and max_depth = 7,) owed the highest average test R2 (0.84), which was suitable for developing a prediction application. Subsequently, through experimental validation with actual biomass, the best GBR multi-task ML model (T ≥ 300 °C, Yield_oil error < 11.75 %, N_oil error < 2.40 %, and ER_oil error < 9.97 %) based on the dataset#6 was obtained for HTL/co-HTL. With these steps, we developed an application for predicting the multi-object of bio-oil, which is scarcely reported in co-hydrothermal liquefaction studies.

Coupling influences of organic components and temperature on nitrogen transformation and hydrochar characterization during hydrothermal carbonization of sewage sludge.

Nitrogen (N) in sewage sludge (SS) should be reduced if it is to be used to produce clean solid fuels. However, the N transformation during hydrothermal carbonization (HTC) of SS is not yet fully understood. Since the composition of SS is complex, it is wise to study a model compound, which should have typical functional groups of organic components. Hence, in this study, six model components (protein, lipid, cellulose, hemicellulose, humic acid, and lignin) representing the main organic components in SS were mixed with SS and treated at 150-270 °C for 1 h. The influence of the organic component and reaction temperature on hydrochar yield, hydrochar characterization, and N distribution in the products was investigated. Except for proteins and lipids, all the other components were found to contribute to the N content and aromatization of the hydrochar. Humus shows the best comprehensive performance in terms of both reducing the N content and increasing the aromaticity. The strongest effects of hemicellulose and cellulose on N retention in hydrochar are found to occur at 210 °C and 240 °C, respectively. The N retention caused by lignin is correlated with the Mannich reaction at 240 °C, while humus significantly promotes N transformation at 240 °C. For carbohydrates, lignin, and humus, the temperatures required for increasing the N content and aromaticity maintain a high degree of consistency. Although protein pulls down the energy recovery (ER) and yield of the hydrochar, observations indicate that it favors the carbonization process. This finding can be used for estimating the N content and quality of hydrochar and provides references for future research targeting the upgrading of hydrochar.

Machine learning for hydrothermal treatment of biomass: A review.

Hydrothermal treatment (HTT) (i.e., hydrothermal carbonization, liquefaction, and gasification) is a promising technology for biomass valorization. However, diverse variables, including biomass compositions and hydrothermal processes parameters, have impeded in-depth mechanistic understanding on the reaction and engineering in HTT. Recently, machine learning (ML) has been widely employed to predict and optimize the production of biofuels, chemicals, and materials from HTT by feeding experimental data. This review comprehensively analyzed the application of ML for HTT of biomass and systematically illustrated basic ML procedure and descriptors for inputs and outputs of ML models (e.g., biomass compositions, operation conditions, yield and physicochemical properties of derived products) that could be applied in HTT. Moreover, this review summarized ML-aided HTT prediction of yield, compositions, and physicochemical properties of HTT hydrochar or biochar, bio-oil, syngas, and aqueous phase. Ultimately, future prospects were proposed to enhance predictive performance, mechanistic interpretation, process optimization, data sharing, and model application during ML-aided HTT.

Characteristics, mechanisms and measurement methods of dissolution and deposition of inorganic salts in sub-/supercritical water.

The efficient and harmless treatment of hypersaline organic wastes has become an urgent environmental problem. Compared to traditional thermochemical methods, supercritical water oxidation has been proven to be an efficient organic waste treatment technology due to the advantages of low cost, high degradation rate, no secondary pollutants, etc. However, the solubilities of inorganic salts drop rapidly near the critical point of water, and some sticky salts form easily agglomerates and then adhere to internal surfaces of reactor and pipeline, causing plugging and inhibition of heat transfer. Hence, the characteristics, mechanisms and measurement methods of the dissolution and deposition of inorganic salts in sub-/supercritical water are summarized and analyzed systematically and comprehensively in this work, intending to provide a valuable guide for salt deposition prevention and subsequent research directions. Firstly, a new classification form of inorganic salt is put forward based on melting point. The phase equilibriums of brine systems are then analyzed in detail. Six theories concerning dissolution mechanisms are discussed deeply and various measurement methods of salt solubility are also supplemented. Furthermore, salt deposition characteristics and related measurement technologies are summarized. Notably, a new idea "hydrothermal molten salt" system is reviewed which may provide a solution for salt deposition in sub/supercritical water. Finally, an outlook for the follow-up researches is prospected and some suggestions are proposed.

Supercritical water co-oxidation behavior in the different monohydric alcohol-ammonia reaction environment.

The degradation of ammonia is a key rate-limiting step during the supercritical water oxidation of nitrogen-containing organics. This paper studied the co-oxidation behavior between different ammonia-alcohol environments, including the influence of reaction parameters and the co-oxidation mechanism. The results showed that increasing temperature, oxidation coefficient, residence time, and alcohol concentration significantly promoted the degradation of NH3-N and TOC, while rising the ammonia concentration enhanced the NH3-N destruction but inhibited the TOC degradation. Alcohols were oxidized first in the co-oxidation system to produce more OH* and HO2* radicals. Ethanol generated the highest concentration of HO2* in the shortest time, leading to more significant ammonia removal than isopropanol and methanol; however, the produced intermediate products like aldehydes and ketones reacted with residual ammonia to generate a small amount of organics at lower temperatures, inhibiting the degradation of alcohols slightly, and combined catalyst or nitrate in the batch reactor or used continuous supercritical water oxidation or supercritical hydrothermal combustion system without controlling the exotherm of fuels could improve this.

A study of impurities in the repurposed COVID-19 drug hydroxychloroquine sulfate using ultra-high-performance liquid chromatography-quadrupole/time-of-flight mass spectrometry and liquid chromatography-solid-phase extraction-nuclear magnetic resonance.

RATIONALE: Hydroxychloroquine sulfate is effective in the treatment of malaria and autoimmune diseases and as an antiviral drug. However, unreported impurities are often detected in this drug, which pose a health risk. In this study, the structures of hydroxychloroquine and six unknown impurities were analyzed using ultra-high-performance liquid chromatography-quadrupole/time-of-flight-tandem mass spectrometry (UHPLC-Q/TOF/MS/MS), and the structures were characterized using liquid chromatography-solid-phase extraction-nuclear magnetic resonance (LC-SPE-NMR) spectroscopy. METHODS: An Agilent InfinityLad Poroshell HPH-C18 column (100 × 4.6 mm, 2.7 µm) was used. For the analysis of hydroxychloroquine and six unknown impurities, the mobile phase was 20 mM ammonium formate aqueous solution and methanol/acetonitrile (80:20, v/v) using gradient elution. Full-scan MS and MS2 were performed to obtain as much structural information as possible. In addition, six unknown impurities were separated by semi-preparative liquid chromatography and characterized using LC-SPE-NMR. RESULTS: The MS2 fragmentation patterns of the impurities were investigated, leading to more structural information and an understanding of the fragmentation pathways of the impurities. The structures of the unknown impurities were confirmed using NMR. In addition, some possible pathways of the formation of the impurities in the drugs were outlined, and these impurities were found to be process impurities. CONCLUSIONS: Based on the identification and characterization of these impurities, this study also describes the cause of the production of the impurities and provides insights for companies to improve their production processes and a scientific basis for the improvement of the related pharmacopoeias.

Review of the destruction of organic radioactive wastes by supercritical water oxidation.

Organic materials, such as ion exchange resins, plastic, oils, and solvents, are widely used in the operation and decommission of nuclear facilities. The generated radioactive organic wastes are both radioactive and organic; therefore, the degradation of such wastes becomes more difficult. Due to delays in the disposal of radioactive organic wastes, potential safety risks are increasing. With the advantages of degrading refractory organics rapidly and thoroughly, supercritical water oxidation (SCWO) has become a potential alternative way to degrade radioactive organic wastes. This review focused on the degradation characteristics of different radioactive wastes from the perspective of potential practical applications. Some improved methods for facilitating the degradation of radioactive wastes by SCWO are considered and analyzed. Moreover, the kinetics and intermediate pathways of radioactive organic wastes are further analyzed. The distribution, migration and transformation of radionuclides during the SCWO reaction, as well as the further processing of radionuclides in gas-, liquid- and solid-phase products, were summarized and discussed. Furthermore, some fruitful areas for further work were reviewed for the highly efficient degradation of radioactive organic wastes. This review can provide useful information and guidance for the industrial applications of SCWO treatment for radioactive wastes.

Chemical reactions of organic compounds in supercritical water gasification and oxidation.

Supercritical water is a benign reaction medium to convert organic matters through supercritical water gasification and supercritical water oxidation into flammable gaseous and harmless substances, respectively. This work systematically summarizes main chemical reactions of some typical organic compounds in supercritical water with or without oxidant for the first time. These compounds include hydrocarbons, proteins, cellulose, lignins, phenols, alcohols, aldehydes, ketones, organic acids, and some N-, Cl-, Br-, F-, S- and P-containing organic matters. Their main conversion pathways, reaction processes, intermediate products, final products and influence factors are analyzed deeply. This information helps to understand and predict corresponding reaction mechanisms and to better achieve objective products in supercritical water gasification and supercritical water oxidation.

Case Report of False Rifampin Resistance with Xpert® MTB/RIF from an HIV Infected Patient.

BACKGROUND: Tuberculosis is one of the main infectious diseases threatening human health, especially in HIV co-infected patients. Xpert® MTB/RIF assay amplifies the rpoB gene of MTB was recommended by the World Health Organization as the initial diagnostic test in cases of suspected infections with Mycobacterium tuberculosis (MTB) or HIV-coinfected TB. METHODS: A 44-year-old male HIV-positive patient co-infected with MTB presented with low-grade fever for 3 months. Rifampicin (RIF) resistance was detected in the celiac pus but not in the pleural effusion using Xpert® MTB/RIF assay. The same samples were then sequenced by next-generation sequencing (NGS) and in-house PCR for rpoB gene. RESULTS: The results of NGS and in-house PCR, however, were paradoxical in the same samples with low or no mutation sequences of RIF resistance. The patient's tuberculosis (TB) therapy was optimized based on first-line anti-TB drugs and antiretroviral treatment. The patient improved with this therapy. CONCLUSIONS: Even with high specificity, false positive results remain possible and RIF resistance detection by Xpert must be considered for clinical interpretation.

Influences of operating parameters on liquefaction performances of Tetra Pak in sub-/supercritical water.

Liquefaction performances of waste Tetra Pak in sub-/supercritical water were evaluated in micro-batch reactors. The influences of temperature (300-420 °C), pressure (16-24 MPa), residence time (5-60 min) and feed concentration (5-40 wt%) on bio-oil yield, high heating value (HHV), and functional groups in bio-oil were investigated. The results showed that bio-oil yield firstly increased with increasing temperature and then decreased when the temperature exceeded 360 °C. Reaction time longer than 30 min gave a negative effect on bio-oil yield. The influence of pressure on bio-oil yield increased markedly from 16 MPa to 22 MPa, and then stabilized. The feed concentration higher than 20 wt% showed little influence on bio-oil yield. Maximum bio-oil yield of 35.55% was found at 360 °C, 22 MPa, 30 min and feed concentration of 20 wt%. HHV and energy recovery efficiency increased significantly with temperature, and maximum HHV of 48.747 MJ/kg and energy recovery efficiency of 46.49% were found at 420 °C, 20 MPa, 30 min and feed concentration of 20 wt%. The main compounds in bio-oil and morphology of the solid residue were also analyzed, and the possible liquefaction pathways of Tetra Pak were proposed.

Supercritical water gasification of phenol over Ni-Ru bimetallic catalysts.

Incorporating Ru in a Ni catalyst for gasification of phenol in supercritical water at 450 °C and 30 min promoted formation of cyclohexanol via hydrogenation, which is a key step toward gasification. Both Ni and Ni-Ru catalysts were effective to reduce the formation of cyclohexanone and oligomerization products, compared with the case with no catalyst. H2 and CH4 yields increased as the Ru/Ni ratio increased, as did the carbon and hydrogen yields in the gas phase products. The Ni80Ru20/Al2O3 catalyst provided good gasification performance and it exhibits Ru (101), Ru (100) and Ni (111) facets and evidence of overlaid bimetallic particles. DFT calculations show that the presence of Ru (either as pure Ru or as a Ni-Ru alloy) reduces the energy barrier for phenol hydrogenation by close to 0.2 eV relative to pure Ni, and that the energy barrier is not as largely affected by the amount of Ru present, provided it is non-zero.

Novel design concept for a commercial-scale plant for supercritical water oxidation of industrial and sewage sludge.

Supercritical water oxidation (SCWO) is a promising chemical technology for organic waste water and sludge treatment. Our team has successfully constructed the first pilot-scale SCWO plant in China, and the design concept for our first commercial-scale plant is reported in this paper. The challenges that hinder the commercial development of SCWO are introduced, including corrosion, plugging, high investment and operating costs. Some important lab-scale and pilot-scale experimental results are shown, and some key design parameters for the commercial plant are proposed. The technological process, specialized equipment design and new system flowsheet are described objectively. Moreover, an estimate of the equipment investment and operating costs of this commercial plant is carried out, and a comparison is made with other commercial sludge SCWO plants. This information is valuable for guiding how to best design commercial SCWO plants for the treatment of sludge and other feedstocks including solid particles.

Stress and bubble pressure response of wet foam to continuous and oscillatory sinusoidal shear.

Wet foam, as a typical multiphase soft material, has complex spatial structure. Foam quality (i.e., gas fraction of a foam fluid), one of fundamental structure parameters of a foam system, generally has a significant influence on the mechanical response of the wet foam to the continuous and oscillatory shear. This study shows that the stress level of the wet foam, including the shear stress and the normal stress difference, rises with the foam quality. An exponential link between the yield stress of wet foam and the foam quality is demonstrated. In the oscillatory sinusoidal shear, a frequent fluctuation of the stress curve mainly occurs at the relatively higher strain rate, and the stress state in the foam is still maintained at the end of the oscillatory shear. Further, with the increase of foam quality, the loss modulus decreases when the foam does not yield, while the storage modulus as well as the loss modulus increases as the strain amplitude exceeds a certain value. Additionally, a nonlinear stress response of the wet foam is mainly attributed to the third harmonic component as the strain amplitude increases in the oscillatory shear. In the shear, the average level of bubble pressure in the foam increases with the foam quality, and it fluctuates with the strain owing to the elastic-plastic deformations of the films. Especially, in the oscillatory shear, the average bubble pressure fluctuates more frequently as the strain rate reaches a relatively higher value.

Ni-Ru/CeO2 Catalytic Hydrothermal Upgrading of Water-Insoluble Biocrude from Algae Hydrothermal Liquefaction.

Hydrothermal liquefaction (HTL) of algae is a promising crude bio-oil (biocrude) production technology, which can convert wet algae into water-insoluble biocrude and other coproducts. In this work, algae HTL at 350°C and 20 min was conducted to obtain water-insoluble biocrude (B1), which was then hydrothermally upgraded at 450°C, 60 min, or with added H2 and/or homemade catalyst (i.e., Ni-Ru/CeO2 or Ni/CeO2) for the first time. The characteristics (e.g., yield, elemental component, energy recovery, and molecular and functional group compositions) of upgraded water-insoluble biocrude (B2) as well as light biocrude thereof were analyzed comprehensively. The results show that Ni-Ru/CeO2+H2 led to the highest yield and HHV (higher heating value), the best elemental compositions quality of B2, and the largest fraction and the best light of light biocrude in B2. Ni-Ru/CeO2+H2 had good catalytic desulfurization effect and could transform high-molecular-weight compounds into low-molecular-weight compounds in B1 upgrading. At the condition above, 46.2% of chemical energy in the initial algae could be recovered by B2, while average 54.9% of chemical energy in B2 was distributed in its light biocrude (hexane-soluble) portion. On the whole, Ni-Ru/CeO2+H2 can be considered as the optimal additive in all tested cases.

Origin of accelerated and hindered sedimentation of two particles in wet foam.

To explore the origin of interactional settling behaviors of multi-particles in wet foam, the sedimentation of two particles placed one above the other as well as placed side by side is studied. According to the average settling velocity in experiment and the average settling drag force of the two particles in numerical simulation, we show that the particles display accelerated sedimentation as placed one above the other while they display hindered sedimentation in the case of the ones positioned side by side. Furthermore, the evolution of structure and force parameters of the bubbles, such as T1 topological events, displacement vector and principal stress fields, shows that the reciprocal action between the foam and the settling particles placed side by side is more significant. The different levels of interplay for these two settling cases also give rise to the diverse changes of bubble pressure response. The bubble pressure component of the average drag force is higher for the particles placed side by side. Especially, for the first time, it reveals that these interactional sedimentation behaviors in the foam are mainly attributed to the changed pressure of bubbles caused by these settling particles at the mesoscopic level. The present results may suggest potential explanations to the cause of the complex accelerated or hindered sedimentation of more particles in wet foam.

Detection of circulating tumor cells by reverse transcription­quantitative polymerase chain reaction and magnetic activated cell sorting in the peripheral blood of patients with hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is one of the most lethal malignancies worldwide. Circulating tumor cells (CTCs) are considered a major cause of recurrence and metastasis in cancer; however, the detection of CTCs is challenging owing to their very low numbers in peripheral blood (around 10 CTCs per 1,000,000 erythrocytes). Cancer­testis antigens (CTAs) are specific tumor markers for CTCs. The present study aimed to evaluate the sensitivity and specificity of reverse transcription­quantitative polymerase chain reaction (RT­qPCR) for the detection of nine CTAs as well as placenta­specific antigen 1 (PLAC1) in peripheral blood mononuclear cell (PBMC) samples collected from 51 patients with HCC. The effectiveness of magnetic­activated cell sorting (MACS) for tumor­cell enrichment, through the depletion of CD45+ leukocytes in PBMC samples, was also assessed. Immunocytochemistry along with hematoxylin and eosin staining demonstrated that RT­qPCR achieved an overall positive detection rate for CTAs and PLAC1 of 70.6%; the highest rates were observed for melanoma­associated antigen A3 (MAGEA3), synovial sarcoma X breakpoint 1, MAGEA1, NY­ESO­1, L antigen 1 and PLAC1. MACS­detected intact CTCs in PBMCs were confirmed by H&E staining and morphological assessment; 12 out of 19 (63.2%) patients were identified as positive for CTAs. Screening for these five CTAs and PLAC1 by RT­qPCR may offer a potentially valuable prognostic tool with good sensitivity and specificity in patients with HCC that may be enhanced by MACS.

Effect of temperature, water loading, and Ru/C catalyst on water-insoluble and water-soluble biocrude fractions from hydrothermal liquefaction of algae.

Hydrothermal liquefaction (HTL) converts algal biomass into a crude bio-oil (biocrude) and aqueous-phase products. The effect of temperature, water loading, and added H2 and/or Ru/C catalyst on the properties of the biocrude that spontaneously separates from the aqueous phase post reaction and also the biocrude that is extractable from the aqueous phase by dichloromethane is explored herein. This report is the first to elucidate how the yields, compositions, heating values, and energy recoveries of the two biocrudes vary with the processing conditions above. Increasing temperature from 350 to 400°C increased the yield of water-insoluble biocrude (38.1-42.5wt%) and its hexane-soluble subfraction (63.7-85.6wt%) while decreasing the yield of extractable, water-soluble biocrude (6.6-2.5wt%). The Ru/C catalyst had the same effect. Reaction temperature and catalysts could be used to manipulate the proportions of water-soluble and water-insoluble biocrude from algae HTL and thereby manipulate biocrude quantity and quality.

Supercritical water oxidation of quinazoline: Reaction kinetics and modeling.

This paper presents a first quantitative kinetic model for supercritical water oxidation (SCWO) of quinazoline that describes the formation and interconversion of intermediates and final products at 673-873 K. The set of 11 reaction pathways for phenol, pyrimidine, naphthalene, NH3, etc, involved in the simplified reaction network proved sufficient for fitting the experimental results satisfactorily. We validated the model prediction ability on CO2 yields at initial quinazoline loading not used in the parameter estimation. Reaction rate analysis and sensitivity analysis indicate that nearly all reactions reach their thermodynamic equilibrium within 300 s. The pyrimidine yielding from quinazoline is the dominant ring-opening pathway and provides a significant contribution to CO2 formation. Low sensitivity of NH3 decomposition rate to concentration confirms its refractory nature in SCWO. Nitrogen content in liquid products decreases whereas that in gaseous phase increases as reaction time prolonged. The nitrogen predicted by the model in gaseous phase combined with the experimental nitrogen in liquid products gives an accurate nitrogen balance of conversion process.

Treatment of municipal sewage sludge in supercritical water: A review.

With increasing construction of wastewater treatment plants and stricter policies, municipal sewage sludge (MSS) disposal has become a serious problem. Treatment of MSS in supercritical water (SCW) can avoid the pre-drying procedure and secondary pollution of conventional methods. SCW treatment methods can be divided into supercritical water gasification (SCWG), supercritical water partial oxidation (SCWPO) and supercritical water oxidation (SCWO) technologies with increasing amounts of oxidants. Hydrogen-rich gases can be generated from MSS by SCWG or SCWPO technology using oxidants less than stoichiometric ratio while organic compounds can be completely degraded by SCWO technology with using an oxidant excess. For SCWG and SCWPO technologies, this paper reviews the influences of different process variables (MSS properties, moisture content, temperature, oxidant amount and catalysts) on the production of gases. For SCWO technology, this paper reviews research regarding the removal of organics with or without hydrothermal flames and the changes in heavy metal speciation and risk. Finally, typical systems for handling MSS are summarized and research needs and challenges are proposed.