[Characteristics of Municipal Solid Waste in Some Urban Agglomeration in the Past Five Years].

The treatment and disposal of municipal solid waste has increasingly become a common concern around the world, and the characteristics of municipal solid waste(MSW) are an important basis for the selection of terminal treatment methods. In this study, more than 400 MSW samples from over 30 cities across China were collected, and the basic physical and chemical properties, such as the physical composition, pollutant content, and calorific value, were analyzed. Shenzhen was taken as an example to analyze the influence of time and waste sorting measures on the physical and chemical characteristics of MSW. The correlation model between MSW composition and calorific value was established using partial least squares(PLS) regression, and the model was verified. The results showed that with per capita GDP increasing by 10,000 yuan, per capita MSW production and the low calorific value of MSW increased by 0.1 kg·(person·d)-1 and 373.8 kJ·kg-1, respectively. However, when per capita GDP was less than 60,000 yuan, the correlation between per capita GDP and per capita MSW production was relatively poor. Kitchen waste was still the most abundant component of MSW, and the content of most samples was between 40% and 60%. The combustible content of rubber/plastic and paper was relatively high, between 20%-30% and 10%-20%, respectively. The inorganic content did not usually exceed 5%, and the moisture content of the MSW was between 50% and 60%. After the implementation of waste classification in 2019, the content of kitchen waste in MSW had been significantly reduced, the content of rubber/plastic had increased, and other components had not changed much. Additionally, the calorific value of waste had been improved to a certain extent. The pollution element contents in MSW, S Cl, and N were all below 1%, and the average value was:N>Cl>S. The contents of Hg, As, Cr, Cd, and Pb in MSW samples did not change significantly with the composition and sampling time, and the content of Pb and Cr in MSW was affected by the environmental background value. The model analysis revealed that rubber/plastics and moisture content were the main variables that affected the calorific value of MSW. The deviation between the measured value and the predicted value was less than 20% for 85.96% of the samples. The model established in this study can meet the needs of the prediction of the calorific value of MSW.

Impact of ball-milling and ionic liquid pretreatments on pyrolysis kinetics and behaviors of crystalline cellulose.

In this work, the kinetic mechanisms of pyrolysis of cellulose with different physical structures were illustrated. The crystalline cellulose showed better thermal stability and required higher energy for decomposition with more concentrated reactions due to the highly ordered structure. The crystallinity of the ball milling and ionic liquid pretreated cellulose decreased and the structure was relatively loose and disordered, thereby reducing the thermal stability, so the global activation energy of both samples decreased and the intensive reaction caused by the collapse of structure was alleviated. In fast pyrolysis, crystalline cellulose favored fast pyrolytic saccharification, and the highest levoglucosan yield reached 64.3 wt% at 400 °C. This research was helpful to deduce the influence of physical structure on the pyrolytic product distribution of cellulose, thereby providing useful information to promote the development of pyrolytic saccharification.

A comparative investigation of fast pyrolysis with enzymatic hydrolysis for fermentable sugars production from cellulose.

In this study, ball milling and ionic liquid pretreatments were utilized to alter cellulose structure prior to fast pyrolysis and enzymatic hydrolysis. The variations in the products distribution of cellulose fast pyrolysis, and their dependence on the structure of cellulose, and the temperature of fast pyrolysis were illustrated. Fast pyrolysis of pretreated cellulose yielded more levoglucosan than crystalline cellulose (14.7%) at 300 °C. Nevertheless, the levoglucosan achieved higher yield (64.3%) from crystalline cellulose at 400 °C. At last, a comparison between fast pyrolysis and enzymatic hydrolysis for cellulose saccharifaction was made. Fast pyrolysis was a promising alternative to liberate levoglucosan from cellulose. Further investigation and development were required to maximize the levoglucosan production.

[Leaching and stabilization of heavy metal in the fly ash of medical wastes].

Through the experiments of leaching and melting on the fly ash of medical wastes, the influence of leaching time, L/S, pH and grain size on the leaching characteristics of heavy metal and the effect of melting on the stabilization of fly ash are studied. Results show that, following the leaching time extending, the leaching concentrations of heavy metals and lixiviate toxicity of heavy metals increase in the fly ash. When the ratio of liquid and solid add, the leaching concentrations of heavy metals obviously become big, and the Cd's leaching concentration is the biggest, when the ratio of liquid and solid is 90, the Cd' s leaching ratio exceed the percent of 70. At the time pH is about 7, the leaching concentrations of heavy metals are the lowest. When the grain size is the bigger or little, the leaching concentrations of heavy metals are lower, however when the grain size is 250-900 microm, the concentrations are higher. After fly ash melt in the high temperature, the lixiviate toxicity of heavy metals greatly reduce, which explains that the effect of melting on heavy metals' stabilization is very good.