Reaction Process of Chromium Slag Reduced by Industrial Waste in Solid Phase

M, a particular industrial waste, was selected to detoxify chromium slag at a high temperature. The carbon remaining in M reduced Cr （ Ⅳ ） of Na2 CrO4 borne in the chromium slag to Cr （ Ⅲ ） in the solid phase reaction, and its thermodynamics and kinetics were studied. The reduction process of Na2CrO4 by carbon produced CO, whiCh＇was endothermic. Under the experimental condition, the apparent activation energy was 4. 41 kJ·mol^-1 , the＇apparent order of reaction for Na2 CrO4 was equal to one, and the partial pressure of CO was only 0.22 Pa at 1 330℃.

FORMATION MECHANISMS AND CONTROL STRATEGIES FOR DIOXINS IN INCINERATION PROCESS OF MUNICIPAL SOLID WASTES

Dioxins, which are of the most toxic materials on the earth, are principal emitted from waste incineration process. The molecular structures, toxicity parameters, such as toxicity equivalency factor, tolerable daily intake and physic-chemical properties of dioxins are briefly summarized. Three formation mechanisms of dioxins in waste incineration process, namely as de novo synthesis, mechanisms involving small organic molecular as precursors and homogenous gas phase reaction mechanism are alto reviewed. The influencing factors for dioxins formation during waste incineration process are also discussed. Three major methods for reducing dioxins emission from waste incineration process are discussed based upon the formation mechanisms and influencing factors. A new waste incineration process with low dioxins emission and low hydrogen chloride corrosion has been proposed based on multi- stage unit operation principal according to formation mechanisms of dioxins and potential production location in waste incinerators.

Waste Minimization Through Process Integration and Multi-objective Optimization

By avoiding or reducing the production of waste, waste minimization is an effective approach to solve the pollution problem in chemical industry. Process integration supported by multi-objective optimization provides a framework for process design or process retrofit by simultaneously optimizing on the aspects of environment and economics. Multi-objective genetic algorithm is applied in this area as the solution approach for the multi-objective optimization problem.

A functionalized activated carbon adsorbent prepared from waste amidoxime resin by modifying with H_(3)PO_(4) and ZnCl_(2) and its excellent Cr(Ⅵ)adsorption

With the application of resins in various fields, numerous waste resins that are difficult to treat have been produced. The industrial wastewater containing Cr(Ⅵ) has severely polluted soil and groundwater environments, thereby endangering human health. Therefore, in this paper, a novel functionalized mesoporous adsorbent PPR-Z was synthesized from waste amidoxime resin for adsorbing Cr(Ⅵ). The waste amidoxime resin was first modified with H3PO4 and ZnCl_(2), and subsequently, it was carbonized through slow thermal decomposition. The static adsorption of PPR-Z conforms to the pseudo-second-order kinetic model and Langmuir isotherm, indicating that the Cr(Ⅵ) adsorption by PPR-Z is mostly chemical adsorption and exhibits single-layer adsorption. The saturated adsorption capacity of the adsorbent for Cr(Ⅵ) could reach 255.86 mg/g. The adsorbent could effectively reduce Cr(Ⅵ) to Cr(Ⅲ) and decrease the toxicity of Cr(Ⅵ) during adsorption. PPR-Z exhibited Cr(Ⅵ) selectivity in electroplating wastewater. The main mechanisms involved in the Cr(Ⅵ) adsorption are the chemical reduction of Cr(Ⅵ) into Cr(Ⅲ) and electrostatic and coordination interactions. Preparation of PPR-Z not only solves the problem of waste resin treatment but also effectively controls Cr(Ⅵ) pollution and realizes the concept of “treating waste with waste”.

Dechlorination Behavior of Mixed Plastic Waste by Employing Hydrothermal Process and Limestone Additive

The usage of plastic-impregnated waste derived solid fuel in conventional combustor is hindered by many technical factors, especially its organic chlorine content. In this paper, experimental study of hydrothermal treatment on mixed plastic waste using the mixture of polypropylene, polystyrene, polyethylene and polyvinyl chloride （PVC） has been performed to observe the dechlorination effect of hydrothermal treatment on the waste. The system was generally applying saturated steam at around 2.4 MPa in a stirring reactor for about 90 minutes. After undergoing the process, the organic chlorine in treated plastic waste was reduced to 1,700 ppm level while the inorganic chlorine content was increased, suggesting an organic chlorine conversion phenomenon to inorganic chlorine, accompanied with low pH due to dehydrochlorination process. Additional limestone （Ca（OH）2） in subsequent experiment showed that the similar phenomenon was occurred but with higher pH and lower chlorine content in the condensed water, suggesting the production of inorganic salt rather than hydrochloric acid. Laboratory scale experiment was also performed to confirm the dechlorination phenomena especially for PVC, and the result showed that the main parameter which affected the dechlorination phenomena was the amount of water in hydrothermal process rather than limestone addition. It is suggested that a combination ofhydrothermal process and alkali addition would produce a low-chlorine solid product from plastic waste, promoting its usage as alternative solid fuel.

Quantification of Flavonoids in Brazilian Orange Peels and Industrial Orange Juice Processing Wastes

The flavonoid content in orange peels of different Brazilian citrus varieties such as bahia, lima, lima-of-persian, morcote, pera, ponkan, seleta, cravo, kinkan and pomelo was assessed. Industry processing juice wastes such as bagasse, bagasse residues, animal feeding bagasse, pulp WEUE and CORE-wash were also analyzed. The HPLC analysis indicates that the most abundant flavonoids found in these Brazilian citrus peels are hesperidin and naringin. The solvents used are selective for flavonoid extraction, and depending on their polarity, glycoside or aglycone flavonoids are extracted. The use of multivariate analysis shows that DMSO is the best solvent to extract glycosides flavanones while hexane displays high selectivity in the extraction of polymethoxylated flavones. The flavonoids present in the orange wastes, obtained at different stages of the industrial processing, are qualitative and quantitatively different. The identification and quantification of the flavonoid composition in each Brazilian citrus variety were evaluated and allowed the selection of the best solvent for the extraction of each specific class of flavonoids. These compounds were found to be more abundant in the fruit peels than in their juices, revealing their great industrial potential. The residual portion of the processing juices is also rich in flavonoids, depending on the processing step.

Green Processes： Transforming Waste into Valuable Resources

1. Introduction Over the next few years, the manufacturing industry worldwide will face intense challenges, as finite supplies of raw materials dwindle and the cheap energy from fossil fuels becomes scarcer. Many conventional manufacturing processes will be outlawed on environmental grounds. For engineers and scientists, these inter- related problems also present an enormous opportunity. Robust new technologies are needed： They must be cost effective and energy efficient, and they must minimize pollution.

Comparative evaluation of processes for heavy metal removal from municipal solid waste incineration fly ash

Hydrochloric acid leaching, chloride evaporation, acetic acid leaching, and biological leaching were evaluated and compared as processes of heavy metal removal for municipal solid waste incineration fly ash(MSWFA). Six factors, namely, energy consumption, process efficiency, process handling, process cost estimation, cost reduction potential, and study progress, were used in order to find out their advantages and disadvantages and to help develop a better recovery process of heavy metals from MSWFA in terms of treatment of the waste material. Hydrochloric acid leaching process was found to be most balanced among the evaluated processes. It showed superiority on energy consumption, process cost estimation, and study progress. On the other hand, despite of its excellency in process efficiency, chloride evaporation process was most unfavorable mainly due to heavy energy dependence. Biological process, with huge potential of cost reduction, was concluded to be the second best process.

Intended process water management concept for the mechanical biological treatment of municipal solid waste

Accumulating operational experience in both aerobic and anaerobic mechanical biological waste treatment （MBT） makes it increasingly obvious that controlled water management would substantially reduce the cost of MBT and also enhance resource recovery of the organic and inorganic fraction. The MBT plant at Gescher, Germany, is used as an example in order to determine the quantity and composition of process water and leachates from intensive and subsequent rotting, pressing water from anaerobic digestion and scrubber water from acid exhaust air treatment, and hence prepare an MBT water balance. The potential of, requirements for and limits to internal process water reuse as well as the possibilities of resource recovery from scrubber water are also examined. Finally, an assimilated process water management concept with the purpose of an extensive reduction of wastewater quantity and freshwater demand is presented.

Computerized simulation of TRPO extraction process treating Chinese high level waste

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A Kind of Lean Approach for Removing Wastes From Non-Manufacturing Process With Various Facilities

It is important to identify and remove the wastes not only from manufacturing process, but also from nonmanufacturing process. In the last several decades, significant research achievements and practice benefits have been achieved about removing wastes from manufacturing process. Since the1990 s, some researchers and lean practitioners have paid more attention to removing waste from non-manufacturing process.Based on the authors' research work and industrial practice, the paper introduces a kind of lean approach for removing waste from non-manufacturing process. In its case study, the order handling process in a value chain is described with respect to a factory and its downstream distribution centers(DCs). The paper proposes a lean approach solution for creating the improved order handling process, and analyze how great improvements in performance can be achieved. As a result, the significant achievement has created a win-win scenario for both the nonmanufacturing process in a factory and non-manufacturing facilities(like DCs) across the value chain. It demonstrates that improvements have been made by removing waste from the non-manufacturing process that takes place within a factory as well as with external participants through the whole value chain. Likewise, the proposed lean approach has helped the case companies to achieve greater levels of efficiency and more benefits. Finally, some conclusions are drawn.

A Review of Co-processing of Kitchen Waste and Municipal Residual Sludge

In this paper, the methods of kitchen waste disposal in recent years were summed up, and the advantages and disadvantages of the current treatment methods were analyzed. At the same time, it has been found that the co-processing of kitchen waste and residual sludge not only has dealt with both kitchen waste and residual sludge, but also the carbon and nitrogen ratio and moisture content of the mixture are balanced, and increases the processing efficiency significantly. It has a certain processing advantage. At present, most research is about the anaerobic digestion of kitchen waste and residual sludge, and the process is more mature, but the study of VFAs accumulation is still insufficient. Aerobic composting is still in the early stage of development, and there are few studies on it at home and abroad. Meanwhile, prospects for the kitchen waste recycling were made in this article.

Valorization of Aloe barbadensis Miller. (Aloe vera) Processing Waste

Aloe vera plant is known worldwide for its medicinal properties and application in gel-based products such as shampoo,soap,and sunscreen.However,the demand for these gel-based products has led to a surplus production of Aloe vera processing waste.An Aloe vera gel processing facility could generate up to 4000 kg of Aloe vera waste per month.Currently the Aloe vera waste is being disposed to the landfill or used as fertilizer.A sustainable management system for the Aloe vera processing waste should be considered,due to the negative societal and environmental impacts of the currents waste disposal methods.Therefore,this review focuses on various approaches that can be used to valorize Aloe vera waste into value-added products,such as animal and aquaculture feeds,biosorbents,biofuel and natural polymers.Researchers have reported Aloe vera waste for environmental applications biosorbents used for wastewater treatment of various pollutants.Several studies have also reported on the valorization of Aloe vera waste for production of biofuels such as bioethanol,mixed alcohol fuels,biogas and syngas.Aloe vera waste could also be valorized through isolation and synthesis of natural polymers for application in wound dressing,tissue engineering and drug delivery systems.Aloe vera waste valorization was also reviewed through extraction of value-added bioactive compounds such as aloe-emodin,aloin and aloeresin.These value-added bioactive compounds have various applications in the cosmetics(non-steroidal anti-inflammatory,tyrosinase inhibitors)and pharmaceutical(anticancer agent and COVID 19 inhibitors)industry.

Whole process reclamation and utilization of wastes produced in the biological fermentation industry

Wastes yielded in the vintage process and the biological fermentation of itaconic acid and sodium gluconate of a winery in Shandong, such as grain stillage, melon lees, cornstarch protein residues, itacanic acid mother liquid, itaconic acid mycelium and sodium gluconate mycelium, were studied. High-activity biological protein feed, foliar fertilizer and irrigation fertilizer were generated from these wastes by applying biological/microbial technologies. Meanwhile, a whole set of technological pathways was put forward. As a result, the optimal economical and social benefits can be obtained with low natural resource consumption and environmental costs by converting wastes into useful matters. In conclusion, through the utilization of limited resources in the whole process of reclamation and utilization of wastes, the harmony promotion can be achieved between the economic system and the natural ecosystem.

Optimization of Biodiesel Production from Waste Vegetable Oil Assisted by Co-Solvent and Microwave Using a Two-Step Process

The two-step catalyzing process for biodiesel production from waste vegetable oil was assisted by both co-solvent and microwave irradiation. Central composite design (CCD) was employed to optimize the reaction conditions. Optimal reaction conditions of the first step were alcohol to oil molar ratio of 9:1, catalyst (H2SO4) amount 1 wt%, reaction temperature 333 K, and reaction time 7.5 minutes;while for the second step, optimal reaction conditions were alcohol to oil molar ratio 12:1, catalyst (NaOH) amount 1 wt%, reaction temperature 333 K, and reaction time 2.0 minutes. The total reaction time was 9.5 min and the conversion rate of fatty acid methyl esters (FAMEs) achieved was 97.4%. The total reaction time was shorter than previous studies. Therefore, the co-solvent and microwave assisted two-step catalyzing process has a potential application in producing biodiesel from waste vegetable oil.

THE EXERGETIC EFFICIENCY OF MSF PROCESS AND THE CONDITIONS OF DESALINATION BY WASTE HEAT

The exergy losses and thermodynamic efficiency of MSF plant with brine recirculation are discussed bymeans of temperature difference functions proposed by the auther.In a MSF plant,the irreversible losses are found mainly in irreversible heat-transfer and flash evaporationprocesses.However,the basic variables are the temperature drop from stage to stage and the temperaturedifferences between flashed vapor and cooling water.In this paper,the flash temperature difference func-tion,the heat transfer temperature difference function and the total temperature difference function are sug-gested.The proposed temperature difference functions of MSF plant provide a convenient tool to analyse theirreversible behavior and evaluate the exergetic efficiency of this system,because without such improvement thecalculation of the exergetic efficiency of a MSF plant according to the classical formula will be not onlyinconvenient but also insignificant.As a result of present analysis,the reasonable parameters based on theenergy consumption are easily chosen.The above-mentioned principles are confirmed by commercial plants and a pilot plant in Tianjin.

Physicochemical Properties and Health Risks of Informal E-Waste Processing at Alaba International Market in Lagos, Nigeria

This study investigated the groundwater quality and health risks associated with informal e-waste processing in the Alaba International Market in Lagos, Nigeria. Twenty-two groundwater samples were collected from hand-dug wells in the market area and analyzed for physicochemical properties and heavy metal concentrations. The results showed that the groundwater quality was poor, with high levels of heavy metals, including cadmium, lead, and chromium. The health index (HI) for children and adults was above the tolerable threshold levels, indicating a potential health risk to the population. Principal component analysis and hierarchical cluster analysis were used to identify the sources of metals in groundwater, and the results showed that informal e-waste processing was a significant source of contamination. The study highlights the need for effective management strategies to mitigate the potential health risks associated with informal e-waste processing and ensure public health and environmental safety.

Co-inhibition of methanogens for methane mitigation in biodegradable wastes

The inhibition effects and mechanisms of chlorinated methane and acetylene on methanogenesis in the anaerobic digestion process of the biodegradable wastes were investigated.It was found that both chloroform and acetylene could effectively inhibit methanogens while the biodegradability of the wastes was not affected.Acetylene inhibited the activity of methanogens,while chloroform inhibited metabolic process of methanogenesis.A central composite design（CCD） and response surface regression analysis（RSREG） were employed to determine the optimum conditions and interaction effects of chloroform and acetylene in terms of inhibition effciency,production of volatile fatty acids（VAF） and molar ratio of propionic acid to acetic acid.Chloroform had significant effect on enhancing the production of VFA（F = 121.3;p 〈 0.01）,and acetylene promoted the inhibition effciency（F = 99.15;p 〈 0.05） more effectively than chloroform（F = 9.72;p 〉 0.05）.In addition,a maximum molar ratio of propionic acid to acetic acid of 1.208 was estimated under the optimum conditions of chloroform concentration of 9.05 mg/kg and acetylene concentration of 3.6×10^-3（V/V）.Hence,methanogens in the wastes can be inhibited while the stabilization process of the biodegradable wastes can still work well,as propionic acid generated during the inhibition process could hardly be utilized by methanogens.

Influence of temperature on performance of anaerobic digestion of municipal solid waste

The influence of temperature on the performance of anaerobic reactors for treating the organic fraction of municipal sohd waste （OFMSW） was studied. Batch digestion of OFMSW was carded out for 32 d at different temperature （25℃, 35℃, 45℃ and 55℃） conditions for total solid concentrations （TS） 17% with the ratio of total organic carbon to nitrogen （C/N） being, 25：1 respectively, while keeping other parameters constant such as inoculum, start-up pH, reactor volume （2 L） and so on. Temperature can influence the methanogenic bacteria activity, accordingly inhibiting the OFMSW biodegradation and stabilization efficiency. Anaerobic reactors excelled at TS reduction, total volatile solid reduction, chemical oxygen demand reduction, increasing cumulative biogas production, whose rate was at temperature （35℃ and 55℃） conditions. Methane concentration in the biogas was above 65% in four reactors. In addition, the fluctuation of temperatures resulted in the biogas production variation. The data obtained indicated that temperature had a significant influence on anaerobic process.