Characterization of Ultrafiltration-Fractionated Humic Acid Derived from Chinese Weathered Coal by Spectroscopic Techniques

Weathered coal is a widely used raw material of farm-oriented humic acid in China, while the high heterogeneity impedes its sufficient utilization. In this study, we fractionated the humic acid derived from Chinese weathered coal by ultrafiltration, and three fractions with the molecular range of ≥100 kDa, 10–100 kDa, ≤10 kDa were obtained. Subsequently, the chemical and spectral properties of the fractions were characterized by elemental analysis, potentiometric titration, Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR), and X-ray photoelectron (XPS) and other spectroscopy. The results showed that more than 60% of humic acid by weight was concentrated in the molecular range higher than 100 kDa, while only 3.25% was assigned to that with molecular weight lower than 10 kDa. The humic acid fraction with molecular weight higher than 100 kDa showed more carbon content, lower H/C atomic ratio, while higher E4/E6 ratio, more aromatic structure in FTIR, 13C NMR, and XPS spectra, indicating a higher degree of aromaticity and stronger hydrophobicity. Conversely, there were more carboxyl groups and aliphatic structures, while fewer condensed aromatic rings for the humic acid fraction with molecular weight less than 100 kDa. These differences provide a baseline for the better utilization of weathered coal.

Bench-scale methanation of pyrolysis gases of Tavantolgoi and Baganuur coals

Bench-scale methanation experiments were performed using the mixture gases evolved in pyrolysis of Tavantolgoi weathered coal and of Baganuur thermal coal. The methanation reactor was composed of the parts of feed gas desulfurization, fixed bed main reactor, condenser and dryer of product gases. The preliminary desulfurized feed gas passed through the fixed bed methanation reactor with the three layers of Ni/Al2O3 catalyst mixed with different amounts of quartz in order to avoid from overheating in upper level of the catalyst. Methanation experiments of pyrolysis gases were performed at temperatures of 250°С and 350˚°С, in a pressure of 3 bar with a GHSV of 9000 h-1. In methanation of pyrolysis gas from the Tavantolgoi weathered coal, CH4 content was increased 10 times from 3.20% to 34.4% at 250°С, however CH4 content was increased 3 times from 9.60% to 29.4% during the methanation of Baganuur coal pyrolysis gas at 350°С. Тавантолгойн болон Багануурын нүүрсний пиролизын хийн метанжуулалтын томруулсан туршилт Хураангуй: Энэхүү судалгааны ажлаар Тавантолгойн ордын исэлдсэн давхаргын нүүрс болон Багануурын ордын үндсэн давхаргын нүүрсний пиролизоос үүссэн хийг метанжуулах томруулсан (бэнч) хэмжээний туршилтыг хийж гүйцэтгэв. Метанжуулалтын томруулсан төхөөрөмж нь хүхэргүйжүүлэгч, конденсатор, чийг шингээгч болон хөдөлгөөнгүй үет реактор бүхий урвалын систем байхаар зохион бүтээсэн. Нүүрсний пиролизын хийг кварцтай хольж Ni/Al2O3 катализаторын гурван үеэр нэвтрүүлж, дулаан дамжуулалтын усгүй шийдлийг хэрэглэсэн. Метанжуулалтын томруулсан туршилтыг 250°С болон 350˚°С температуруудад, 3 бар даралтанд, 9000 h-1 түүхий эдийн урсгал хурдтай нөхцөлд хийж гүйцэтгэв. Тавантолгойн ордын исэлдсэн давхаргын нүүрсний пиролизын хийг метанжуулахад бүтээгдэхүүн хий дэх метаны агуулга 3.20%-иас 34.4% хүрч 10 дахин ихсэж, харин Багануурын нүүрсний хийнээс үүссэн метаны агуулга 9.60%-иас 29.4% болж 3 дахин ихэслээ. Хэдийгээр метанжуулах процессын температур харьцангуй нам байсан боловч Тавантолгойн ордын исэлдсэн давхаргын нүүрсний пиролизын хийн метанжуулалтын дүнд үүссэн метан хийн агуулга нь Багануурын ордын үндсэн давхаргын нүүрсний пиролизын хийтэй харьцуулахад 5.01%-иар их байлаа.

Removal of Cd(II) from Water by HPEI Modified Humin

Humin is the waste residue from the process of preparing humic acid, which accounts for a large proportion of the raw material (weathered coal humic acid). Its Cd(II) adsorption performance is far inferior to that of humic acid. How to regenerate humin is of great significance to the low-cost treatment of Cd(II) pollution in wastewater. In this study, humin was modified by hyperbranched polyethyleneimine to enhance the adsorption capacity for Cd(II). Fourier transform infrared spectroscopy and the X-ray photoelectron spectrometer showed that hyperbranched polyethyleneimine was grafted to the surface of humin. Flame atomic absorption spectroscopy showed that the saturated Cd(II) adsorption capacity of the modified humin was increased to 11.975 mg/g, which is about 5 times than that of humin and is also higher than that of humic acid. The adsorption kinetics, adsorption isotherm, and thermodynamic properties of humic acid, humin, and modified humin were also studied. This study may provide a foundation for research utilizing natural resources to reduce heavy metal pollution in the environment.

Effect of particle size on indicator gas emission during high-temperature oxidation of weathered coal

<p>Coal spontaneous combustion is one of the severe nature hazards among nature resources. There are many influence factors which control the development of spontaneous combustion such as particle size, oxygen concentration, etc. Weathering effects alter the spontaneous combustion characteristics of coal. To explore the effect of particle size on gas emission from weathered coal under high temperature oxygen deficiency, the macroscopic spontaneous combustion characteristics of weathered coal with various particle sizes in high temperature oxidation process were studied. The gas concentration of different particle sizes with weathered coal oxidation from normal temperature to 600 °C was tested by the self-built high temperature program experiment system, and the variation law of the indicator gas was analyzed. The results showed that there were different experimental phenomena in each particle size coal sample. The concentration of indicator gas neither increased nor decreased monotonically with the change of particle size. Roughly, 3 mm is the critical particle size in the process of high temperature oxidation of weathered coal. The experimental results provided a pivotal theoretical basis for the early prediction and the scientific prevention of the spontaneous combustion of the weathered coal during the mining process of the open pit and the shallow coal seam.</p>