Hydrothermal carbonisation of polyvinyl chloride in ethanol-water/water system for solid fuels: Dechlorination, characteristics analysis of hydrochar, and reaction path.

Polyvinyl chloride (PVC) waste plastic is a typical solid waste. In this paper, the dechlorination and carbonization behavior of PVC in ethanol-water/water system under different process parameters (temperature, residence time, solid-liquid ratio) was studied, and hydrothermal carbon was characterized by SEM, elemental analysis, TG-DTG, XPS, Py-GC/MS. The results show that temperature is the key to the hydrothermal dechlorination of PVC, and the dechlorination efficiency of PVC is the highest by parameter optimization (220°C-90 min-10% S/D-80% E/D), which can reach 96.33 %. With the removal of Cl, the surface of the PVC matrix changed from full and smooth flocculent to honeycomb with uniform pore size distribution. Thermogravimetric analysis shows that the combustion of hydrochar can be divided into three stages: HCl precipitation and volatile combustion, semi-coke and coke combustion, and fixed carbon combustion. The combustion parameters and kinetic parameters of hydrochar were measured, and it was found that the hydrothermal carbonization of PVC at higher temperatures and ethanol-water ratio could improve the combustion performance of hydrochar. The highest calorific value can reach 36.68 MJ/mol. Py-GC/MS analyzed the distribution of the pyrolysis products, and alkylbenzene and aliphatic were the main products of pyrolysis. The structural analysis of hydrochar showed that C-C and CC accounted for the largest proportion, accompanied by a small amount of C-O and CO and trace C-Cl. The possible reaction mechanism of the hydrothermal carbonization of PVC was analyzed based on the distribution of functional groups and compound composition. This work provides an effective and sustainable method for the recycling of refractory chlorinated plastics.

Research progress in improving sludge dewaterability: sludge characteristics, chemical conditioning and influencing factors.

Sludge from wastewater treatment processes with high water content and large volume has become an inevitable issue in environmental management. Due to the challenging dewatering properties of sludge, current mechanical dewatering methods are no longer sufficient to meet the escalating water content standards of sludge. This paper summarizes the characteristics of various sludge and raises reasons for the their dewaterability differences. Affected by extracellular polymeric substances, biological sludge is hydrophilic and negatively charged, which limits the dewatering degree. The rheological properties, flocs, ionic composition, and solid phase concentration of the sludge also influence the dewatering to some extent. For these factors, the chemical conditioning measures with simple operation and excellent effect improve its dewaterability, which mainly include flocculation/coagulation, acid/alkali treatment, advanced oxidation, surfactant treatment and combined treatment. There is a growing necessity to explore the development of new chemical conditioning agents, even though traditional agents continue to remain widely used. However, the development of these new agents should prioritize finding a balance between various factors such as efficiency, effectiveness, ease of operation, environmental safety, and cost-effectiveness. Electrochemical dewatering enhances solid-liquid separation, and its coupling with chemical conditioning is also an excellent means to further reduce water content. In addition, the improvement of press filter is an effective way, which is influenced by pressure, processing time, sludge cake thickness and pore structure, filter media etc. In general, it is essential to develop new conditioning agents and enhance mechanical filtration press technology based on a thorough understanding of various sludge properties. Concurrently, an in-depth study of the principles of mechanical pressure filtration will contribute to establishing a theoretical foundation for effective deep sludge dewatering and propel further advancements in this field.

Magnetic-Fluorescent Responsive Janus Photonic Crystal Beads for Self-Destructive Anti-counterfeiting.

In this study, we fabricate magnetic-fluorescent responsive Janus photonic crystal beads (JPCBs) based on poly(styrene-methyl methacrylate-acrylic acid) (p(St-MMA-AA)) colloidal nanoparticles, Fe3O4, and photobase generators used for self-destructive anti-counterfeiting. We synthesize two kinds of photobase generators that can react with fluorescamine to produce various fluorescence colors. A microfluidic method is used to obtain the Janus photonic crystal beads. The upper portions of the JPCBs are photonic crystals assembled with colloidal spheres, whereas the Fe3O4 settles down to the bottom of the JPCBs due to its higher density. Photobase generators are distributed in photonic crystal gaps. Because of the magnetism of the Fe3O4, the JPCBs could be flipped from one side to the other in the presence of a magnet. After being exposed to UVC light and fluorescamine, the JPCBs can fluoresce under UVA light. Then, we create Janus microbeads arrays with various types of beads and apply them to the visitor card, bracelet, and box label to provide irreversible and self-destructive anti-counterfeiting. The JPCBs are capable of being encoded and angle-independently displayed, which are crucial to their applications in anti-counterfeiting, information coding, and array display.

Methods, mechanisms, models and tail gas emissions of convective drying in sludge: A review.

In tandem with the population and economic growth worldwide, the scale of wastewater treatment has been increasing each year. Thus, a large amount of sludge is being produced. If the problem of sludge treatment and disposal cannot be effectively solved, it will cause serious environmental pollution. The premise of sludge drying is that sludge is "harmless" and can be "recycled." Currently, the studies on convective drying focus on the direction of thin-layer drying, fluidized bed drying, spray drying and pneumatic drying. This paper systematically reviews the convective drying technology of sludge. First, the effects of air velocity temperature, relative humidity and particle size on the drying effect are precisely described, as well as the four different drying stages in the drying process, including preheating, constant rate drying, first falling rate drying, and second falling rate drying stages. Second, the research progress of different convective drying treatment technologies and the application of eight mathematical models of thin-layer drying in this field are elaborated. The effects of sludge shrinkage formation mechanisms and sludge viscous resistance generation during the drying process are also discussed in detail. The formation mechanism of sludge shrinkage and the effect of sludge viscosity resistance during drying are also elaborated. Finally, the main dry tail gases and restraining methods are elaborated during the drying process. This paper will provide a structured reference for the related research of sludge convective drying in the future.

Effects of aqueous phase circulation and catalysts on hydrothermal liquefaction (HTL) of penicillin residue (PR): Characteristics of the aqueous phase, solid residue and bio oil.

Hydrothermal liquefaction (HTL) is a promising thermochemical technology for the treatment of hazardous wastes such as penicillin residue (PR). For the treatment of aqueous waste produced by PR in the HTL process, aqueous phase circulation is an attractive solution, both environmentally and economically. The present study shows that aqueous phase circulation can promote the transfer of organic matter from the aqueous phase to bio-oil. The content of organic acids and alcohols in the aqueous phase decreased significantly, and the bio-oil yield and energy recovery efficiency also increased. Under non-catalytic conditions, the bio-oil yield increased from 26.09 wt% to 33.72 wt%. The use of Na2CO3 as a catalyst further improved the bio-oil yield. After a single aqueous phase circulation, the bio-oil yield increased to 34.63 wt%, and the energy recovery efficiency increased to 66.94%. Under catalytic hydrothermal conditions, the content of organic acids in the bio-oil was reduced using aqueous phase circulations, which improved the quality of the bio-oil. At the same time, the Na2CO3 catalyst promoted the hydrolysis of PR to form small molecule organic matter, inhibited the formation of coke, and reduced the content of carbon, hydrogen and oxygen in the solid residue. An increase of cycle times led to excessive accumulation of Na2CO3, which had a negative impact on the yield of bio-oil. Nitrogen-containing compounds in the bio-oil increased to a certain extent, which renders it necessary to consider denitrification treatments in the future. The work provides a useful reference for further research on the preparation of high quality bio-oil by PR hydrothermal liquefaction.

Catalytic upgrading of penicillin fermentation residue bio-oil by metal-supported HZSM-5.

Antibiotic fermentation residue (AR) is composed of hazardous organic waste produced by the pharmaceutical industry. AR can be effectively converted into bio-oil by fast pyrolysis, but its high nitrogen content limits the prospect of bio-oil as a fuel resource. In order to further reduce the nitrogen content of AR bio-oil, we have examined the catalytic removal of N and O from penicillin fermentation residue (PR) bio-oil under fast pyrolysis conditions. We have used M/HZSM-5 (M = Fe, Co, Ni, Cu, Zn, Zr, Mo, Ag and Ce) metal catalysts, with a metal oxide content of 10%. Additionally, the effect of mixed and separated catalytic forms on catalytic upgrading were analyzed, and changes in the catalyst itself before and after pyrolysis under separated catalytic conditions were specifically investigated. Our results show that the metal elements in the fresh catalyst will exist in the form of oxides, ions and simple metals. In-situ reduction caused by pyrolysis gas in the catalytic pyrolysis process makes some ionic metals (e.g., Co2+, Cu2+ and Ag+) in the catalyst transform into oxides, and some metal oxides are reduced to simple metals or suboxides (including Fe, Ni, Cu and Mo). The N content in the mixed catalytic bio-oil decreased from 10.09 wt% to Zn/HZSM-5 (6.98 wt%), Co/HZSM-5 (7.1 wt%), Cu/HZSM-5 (7.18 wt%) and Ce/HZSM-5 (7.18 wt%). We also observed significant reduction in the O content (9.77 wt%) with Ag/HZSM-5 (3.75 wt%), Mo/HZSM-5 (6.86 wt%), Ce/HZSM-5 (8.39 wt%) and Fe/HZSM-5 (8.54 wt%) in the separated catalytic bio-oil. The Ni/HZSM-5 catalystcan reduce the organic acid content in bio-oil from 22.9% to 10.8%. The separated catalysis methodology also promoted an increase of hydrocarbons in the bio-oil: Zn/HZSM-5, Ag/HZSM-5, Mo/HZSM-5, Zr/HZSM-5 and Ce/HZSM-5 reached 11.6%, 11.5%, 11.1%, 10.1%, and 8.8%, respectively. Carbon deposition formed by aromatic carbon/graphite carbon, pyrrole and pyridine compounds leads to deactivation of the catalyst.

Preparation of bio-oils by hydrothermal liquefaction (HTL) of penicillin fermentation residue (PR): Optimization of conditions and mechanistic studies.

Response surface methodology (RSM) was used to investigate factors influencing the yield of bio-oil from the hydrothermal liquefaction (HTL) process of penicillin fermentation residue (PR). The reaction mechanism of the HTL was also studied. The hydrolysis of organic compounds in PR was enhanced, and the bio-oil yield increased with an increase of temperature. When the temperature rose from 280 °C to 320 °C, the yield of bio-oil decreased due to condensation and pyrolysis. Both the residence time and total solid content had effects on the bio-oil yield. The predicted values from the RSM model was in good agreement with the experimental values. Optimized conditions showed that the predicted value of the highest bio-oil yield was 25.91 wt%. The optimized reaction conditions were as follows: reaction temperature was 300 °C, residence time was 174 min, and total solid content was 18 wt%. The bio-oil was analyzed by GC-MS, and showed that it consisted mainly of hydrocarbons, nitrogen-containing heterocyclic compounds, and oxygen-containing compounds. Finally, the formation mechanism of these components and their possible reaction paths are presented and discussed. The results will provide useful guidance for regulating the characteristics of antibiotic residues, and realizing their further utilization as a chemical feedstock.

Nitrogen release of hydrothermal treatment of antibiotic fermentation residue and preparation of struvite from hydrolysate.

Hydrothermal treatment (HT) is an appropriate treatment method for organic hazardous wastes such as antibiotic fermentation residue (AR). However, there is no effective way to recycle hydrolysate with high nitrogen content. In this study, penicillin fermentation residue (PR, a type of AR) was used as raw material to study the release and redistribution of N during hydrothermal process. And the influences of pH, ion ratio and reaction time on the preparation of struvite were analyzed. The results showed that the nitrogen in PR consists of Inorganic-N and Amino-N. Most of N (~70%) that entered hydrolysate was converted into org-N, NH4+-N and NO3--N. At 260 °C, the NH4+-N concentration was 2842.78 mg/L, accounting for 45.2% of total nitrogen. The remaining amino-N in the hydrochar was gradually converted to pyridine-N, pyrrole-N and quaternary-N with the increasing of temperature. At pH = 9.5, Mg2+: NH4+: PO43- = 1.3: 1: 1.15, struvite was prepared by hydrolysate. And over 95% removal rate of NH4+-N could be achieved. XRD analysis showed that the main component of the product was struvite, which was further confirmed by SEM-EDX and FT-IR. It was found that there was trace amount of MgKPO4·H2O precipitation in the product. In addition, Mg3(PO4)2 precipitation might also be formed at pH = 10.

Thermal characteristics and product formation mechanism during pyrolysis of penicillin fermentation residue.

This work studied thermal characteristics and product formation mechanism during pyrolysis of penicillin fermentation residue (PR). Results showed that PR pyrolysis proceeded in four stages. The kinetic triplet of each stage was calculated using Flynn-Wall-Ozawa, Kissinger-Akahira-Sunose, and integral master-plot methods. The kinetic model for stage 1 was the three-dimensional diffusion model, the simple reaction order model for stage 2 and stage 4, and the nucleation-growth model for stage 3. FTIR analysis suggested that the intensities of absorption peaks of NH, CO, CH, CN, and CO in chars weakened gradually with increasing temperature, corresponding to the production of CH4, CO, NH3, and HCN. GC-MS results indicated that the high protein content in PR resulted in a high fraction of nitrogenated compounds (amides and amines, nitriles, and N-heterocyclic species) in bio-oil. The formation mechanism of these compounds was discussed. Besides, bio-oil also contained large quantities of oxygenated compounds and a few hydrocarbons.