Potential importance of organic matters to explain particle size effect on water holding capacity of natural soils and river sand with/without coal fly ash amendment and its complicated dependency on temperature

( Mengzhu Song ),( Shenglei Lin ),( Fumitake Takahashi ) 한국폐기물자원순환학회(구 한국폐기물학회) 2016 한국폐기물자원순환학회 춘계학술발표논문집 Vol.2016 No.-

Huge amounts of fly ash (FA) are generated through the combustion processes of coal-fired power plants every year in worldwide. Environmental adverse impacts caused FA without utilization and the deterioration of desertification in arid areas are both severe problems. This study aims to recycle coal FA as water holding agent for deteriorated soil in arid area solve both FA management and anti-desertification problems. The effect of FA amendment on water holding capacity (WHC) of natural soils and sands with different size distributions was focused on. Decomposed granite soil (DGS), akatama soil (AS), and river sand (RS) were used. FA-mixed soil/sand samples were dried at room temperature and 40 °C, and their moisture losses were measured in an hour interval. The results showed that particle size of soil/sand has an effect on WHC. The highest/lowest WHC appeared in certain range of particle size and it also depends on soil/sand type and temperature. For example, in the case of DGS under natural condition, size range of 75-150 μm reaches the maximum, and highest WHC appears at size range of 1-2 mm at 40 °C; AS has the highest WHC at size range of 150-250 μm under natural condition, however in this size range it has lower WHC than the average at 40 °C; RS with 75-150 μm size range has lower WHC than the average under natural condition but has second highest WHC at 40 °C. One-sided Welch’s t-test suggested that the size dependency of raw FA amendment on WHC was regarded as significant in those cases even when experimental errors were taken into account. In addition, WHC also depends on the temperature. Optimum size range for the highest WHC shifts to smaller or larger size range when drying temperature changes. On the other hand, complex effects of FA amendment on WHC were found. Although FA amendment decrease soil/sand WHC in many cases, increases of WHC were also found in particular at 40 °C. These negative/positive effects of FA amendment on WHC can be concluded as negligible or within experimental errors. Weltch’s t-test was used to check the statistical significance of WHC difference among pure soil and FA-amended soil with the same size range, and limited cases were found as significant. This also supports lower effect of FA amendment on WHC than size effect. WHC variation as a function of soil/sand size can be found obviously in those results regardless of FA mixing ratio. Although drying temperature changes optimum size range for the highest WHC, optimum size range did not depend on FA amendment in almost all cases. This suggests that FA amendment effect is also smaller than temperature effect. The effect of soil/sand size on WHC was much larger than FA amendment effect and it could be explained partially by organic matter concentration in soil/sand fractions. Weight ratios of organic matter in the different size fractions of pure soUs and sand were measured. Positive or negative correlations were found between WHC and organic matter. For example, in the cases of DGS and AS under natural condition, the correlations are positive. This means that WHC of DGS and AS increases with the increase of organic matter weight ratio. In the cases of RS under natural condition, however, the correlations are negative. The increase of organic matter decreased sand WHC. Therefore, the correlation between WHC and organic matter shows soil/sand type dependency. On the other hand, the correlation changes contrastingly at 40 °C. This means that the dependency of soil/sand WHC on organic matter also depends on drying temperature. It might be explained by characteristic change of organic matter induced by temperature. High temperature might affect some types of organic matter contained in soil/sand, change its affinity to water, and thus change organic matter effect on WHC. Soil/sand WHC has complicated dependency on the type of organic matter, its concentration, and temperature. Therefore, FA modification is recommended to increase soil/sand WHC by FA amendment, and it should also be tested at different temperatures.

Effect of polymer-treated fly ash amendment on water retention capacity of soils and sands

( Mengzhu Song ),( Shenglei Lin ),( Fumitake Takahashi ) 한국폐기물자원순환학회(구 한국폐기물학회) 2018 한국폐기물자원순환학회 심포지움 Vol.2018 No.1

Coal is one of the major energy sources worldwide. Coal provides around 30.1% of global primary energy needs and generates over 40% of the world’s electricity. Fly ash (FA) is one of the major solid waste by-products from the combustion processing of coal fired power generation. In the worldwide level, huge amounts of FA are disposed every year. For example, the utilization ratio of FA in India is only around 38% with the annual FA generation that over 100 Mt. In China, FA utilization is about 60% and the total annual FA generation is about 500 million tons (Mt). In the United State, more than 136 Mt of coal combustion wastes are generated per year. Huge amounts of FA are disposed and accumulated in landfill sites or dumps, which causes severe social and environmental problems. On the other hand, severe land degradation is now affecting 168 countries across the world, threatening arid/semi-arid areas like western China. In order to keep and increase soil productivity with limited water resources, water retention agents for soil are very attractive. In addition, coal is usually a major power source in arid areas like western part of China. Therefore, arid areas with rich coal resources have faced desertification and FA management problems at the same time According to some reports, FA could have a great potential in agricultural applications because of its properties like texture, bulk density, pH, and high concentration of nutrition elements. Therefore, this research focused on FA application for soil amelioration to improve water retention capacity of the soil. Materials used in this study are akatama soil (AS), silica sand (SS) and coal fly ash. For FA modification, two kinds of polymer treatment were tested. In polyvinyl alcohol (FVA) treatment, FA was mixed with the solid particles of completely hydrolyzed polyviylalcohol (PVA). Mixing ratio of FVA is 20 wt%, and the average molecular weight of PVA is 1,000 Da. In polyacylic acid (PAA) treatment, FA was mixed with the solid particles of PAA at 20 wt% of PAA mixing ratio. The average molecular weight of PAA is 25,000 Da. In both treatments, water retention capacity (WRC) measurement was conducted under unsaturated condition by drying experiment. In this method, WRC means water evaporation resistivity under water-unsaturated condition rather than retainable water in soil at certain pressure. FA was mixed with dried sands and soils at mixing ratios of 10 wt%, 20 wt% and 30 wt%. Initial moisture content was adjusted at 30 wt% for each sample. All the samples were dried at 40 °C in an incubator. The weights of the samples were measured for 12 hours at one-hour interval to monitor water retention in the samples. Moisture weight at each drying time was normalized by the initial moisture weight to draw water retention curve. WRC was defined as the area under the water retention curve. According to experimental results, WRCs of SS and AS were all increased by amendment of PVA-modified FA at 40 °C. WRC of SS and AS was increased by 23% and by 26% at 20 wt% of mixing ratio, respectively. Welch’s t-test suggested that the increase of WRCs of SS and AS were statically significant. When the mixing ratio of FA was 30 wt%, the WRCs of SS and AS were both decreased compared to those at 20 wt% of mixing ratio. Excess amendment of polymer-treated FA might cause negative effect on the WRC. Experimental results of PAA-modified FA amendment showed that the effect of PAA treatment of SS was positive. WRC of SS was increased by 35% when the mixing ratio of FA is 20 wt %. The positive effects of PAA-modified FA amendment on WRC of SS was also regarded as statically significant by Welch’s t-test. However, this study also found that the effect of PAA treatment on WRC of AS was limited or negligible.

Effect of Raw Fly Ash on Water Holding Capacity of Different Sizes Distributed Soil and Cellulose Treatment of Fly Ash

( Mengzhu Song ),( Shenglei Lin ),( Yun Li ),( Lifen Liu ),( Fumitake Takahashi ) 한국폐기물자원순환학회(구 한국폐기물학회) 2015 한국폐기물자원순환학회 3RINCs초록집 Vol.2015 No.-

Environmental pollution caused by huge amount of generated coal fly ash (FA) without utilization and the deterioration of desertification in arid areas are big social problems. This study investigated the effect of raw coal fly ash amending on water holding capacity (WHC) of decomposed granite soil (DGS) and Akatama soil (AS) with different size distribution. Cellulose treated FA was also tested in the experiment, as an investigation on the polymer grafting method of FA modification, to try to increase the positive effect on WHC of soil. The test soil was dried at room temperature and 40 ºC respectively, and its moisture loss was monitored per hour. The particle size has an effect on WHC, and the relationship between the particle size and WHC is not a leaner relationship. It shows there WHC has the dependency on soil particle size and there are peak points of the WHC curve at certain ranges of particle size. In general, raw FA has a positive effect on the WHC of DGS and AS. However, cellulose-treated didn’t have a significant positive effect on WHC of DGS. This study shows that the impact of FA on WHC is complex, and many factors can influence WHC such as particle sizes, drying temperature, soil type, mixing ratio of FA, and FA treatment type.

Effect of amending coal fly ash on water retention capacity of sands: Surface modification tests using polymer treatment

( Mengzhu Song ),( Shenglei Lin ),( Fumitake Takahashi ) 한국폐기물자원순환학회(구 한국폐기물학회) 2017 한국폐기물자원순환학회 심포지움 Vol.2017 No.1

Fly ash (FA) is one of the major solid waste by-products from the combustion processing of coal fired power generation. In the worldwide range, huge amounts of FA are disposed without any treatment every year. For example, the utilization ratio of FA in India is only around 38% with the annual FA generation that over 100 Mt. In China, FA utilization is about 60% and the total annual FA generation is about 500 Mt. Huge amounts of FA are disposed and accumulated in landfill sites or dumps, which causes severe social and environmental problems because FA occupied large area for disposal and contains toxic elements that can cause environmental pollution. Therefore, new applications of FA are significantly required. On the other hand, land deterioration and following desertification is also a severe problem in arid areas. Some soil amending materials to increase soil water retention capacity are very important and useful for anti-desertification. FA has a great potentials in agricultural applications because its properties like texture, bulk density, pH, and high concentration of nutrition elements (K, Na, Zn, Ca, Mg and Fe) seems to be able to serve for soil modification and increase the yield of agricultural crops. Therefore, this study aims to recycle FA as a soil amending material to improve water retention capacity of the soil. This may give a promising solution of both FA recycle management problem and desertification problem at the same time. Materials used in this study are river sand (RS), silica sand (SS) and coal fly ash. For FA surface modification, polymer treatment was utilized. In dry treatment, FA was mixed with the solid particles of polyethylene glycol (PG). In wet treatment, FA was mixed with the solution of PG. In both treatments, the mixing ratio of PG is 5 wt%. Water retention capacity (WRC) measurement was conducted under unsaturated condition via drying experiment. In this method, WRC means water evaporation resistivity under water-unsaturated condition rather than retainable water in soil structure at certain pressure. There were two drying setups that under natural condition and at 40 °C in an incubator, respectively. FA was mixed with dried sands at mixing ratios of 10 wt%, 20 wt% and 30 wt%. Initial moisture content was 30 wt% for each sample. The weights of the samples were measured for 12 hours at one hour interval to monitor water retention in the samples. Moisture weight at each drying time was normalized by the initial moisture weight to draw water retention curve. WRC was defined as the area of water retention curve. According to experimental results of dry-treatment, WRC of SS and RS were all increased by the PG modified-FA at room temperature and 40°C. However, under both temperature conditions, the effects of dry-modified FA on WRC of sands were limited although Welch’s t-test suggested that the increase of WRC of SS was statically significant. On the other hand, the WRC of RS and SS were all decreased by wet-modified FA amendment compared to the results of diy-modifed FA. In the case of SS with wet-modified FA, the WRC is the lowest when the mixing ratio of PG modified-FA is 10 wt%. Experimental results can be concluded that the effect of wet PG-treatment of FA on the WRC of sands was negative. Although the WRC of sands can be increased by amending dry-modified FA, the effect is limited. In addition, the hysteresis effect should also be concerned. In the natural environment, the rainfall possibly could reduce the positive effect of PG-modified FA on water retention of soil afterwards.

Surface and thermal properties of geocasted municipal solid waste incineration fly ash composites

( Giun Jo ),( Mengzhu Song ),( Patcharanat Kaewmee ),( Astryd Viandila Dahlan ),( Fumitake Takahashi ) 한국폐기물자원순환학회(구 한국폐기물학회) 2019 한국폐기물자원순환학회 심포지움 Vol.2019 No.1

Municipal solid waste (MSW) generation is rapidly increasing in many developing countries owing to population and economic growths. Therefore, reducing MSW is a major issue in the world. In Japan, the incineration is one of the major treatments for reducing MSW volume and weight. Specially, MSWI ashes, which are bottom ash and fly ash, have great potential for recycling in various field such as construction. However, fly ash contains heavy metals like Pb and Zn. Therefore, it might cause environment pollution when they are recycled without any treatment. Chelate treatment for immobilizing hazardous heavy metals in fly ash has possibility of chemical/biological decomposition of chelate-metal complex and might cause long-term high concentration of organic hydrocarbons in landfill site as well as leaching of heavy metals to the environment. In this research, the authors targeted fluidized-bed incinerator fly ash. Fluidized-bed incinerators produce only fly ash and its application is strongly requested in Japan. To replace sand by fly ash, aggregating was required to adjust appropriate particle size in order to comply with physical requirements of heat carrier in fluidized bed combustors. This research utilized geocasting method to create sand-alternative heat carrier using fly ash. When fly ash are recycled as heat carrier, thermal treatment of fly ash is also expected for further immobilization of heavy metals contained in fly ash. In this research, the authors measured surface morphology by scanning electron microscope (SEM), heavy metal leachabilities by leaching tests, surface area by nitrogen adsorption based on Brunauer-Emmett-Teller model (BET), and thermal stability by thermogravimetric analysis. The results demonstrated geopolymer by calcined condition effects improved heavy metal immobilization value, and porous characteristic and heavy metal immobilization were influenced by high temperatures.

Effect of amending coal fly ash on water retention capacity of soils and sands: Surface modiflcation tests using organic reagents

( Shenglei Lin ),( Mengzhu Song ),( Fumitake Takahashi ) 한국폐기물자원순환학회(구 한국폐기물학회) 2017 한국폐기물자원순환학회 심포지움 Vol.2017 No.1

Coal fly ash (FA) and bottom ash (BA) are two major by-products from coal-fired power generation. Global FA generation is estimated to be 750 million Mg/yr. FA disposal at open-air dumping site and/or landfilling without appropriate management have caused air, water, and soil pollutions around dumping sites and has raised an environmental concern according to potential emission of toxic elements contained in FA. Therefore, an efficient way to recycle FA is required. This research focuses on FA application for soil amelioration, in particular water holding agents from the view point of anti-desertification. Materials used in this study are decomposed granite soil (DGS), akatama soil (AS), silica sand (SS) and coal fly ash. For FA surface modification, organic treatment was utilized. FA was mixed with saturated sucrose and cellulose solution. Mixed materials were burned at 500 °C for 3 hours and crushed for sample homogenization. Water retention capacity (WRC) of soil and sand, raw/modified FA, were measured by drying experiments. 7.5 g of pure water was added to 17.5 g of dried sample to adjust initial water content as 30 wt%. FA amending ratios are 10 wt%, 20 wt% and 30 wt%. Moistened samples were dried under natural condition (around 20 °C) or dried isothermally in an oven at 40 °C for 12 hours. The weights of moistened samples were measured at 1 hour intervals to monitor water retention in the sample. According to drying experimental data, water retention curves were drawn, which are weight-based relative percentages of remained water in the sample at different drying times. WRC amount (h) is calculated from area of water retention curves. WRCs were compared to figure out effect of organic treatment on surface modification of FA and effect of amending FA on water retention capacity of soil and sand samples. According to SEM observation, raw FA showed isolated sphere particles and smooth surface, while FA aggregation was built up by cellulose and sucrose. Some porous surfaces were created in cellulose modification as shown in SEM observation (See Figure 1). According to experimental results at room temperature, WRC of SS, RS, raw FA, and organic modified FA are almost the same. At 40 °C, WRC of samples varied a lot WRC of all samples decreased with the increasing of temperature. Mixing FA modified by cellulose and sucrose decreased WRC of DGS. While different from sucrose-modified FA, cellulose-modified FA increased WRC of AS and SS. As an example of experimental results, Figure 1 shows SEM pictures of modified FA and the effect of modified FA amendment on WRC of samples at 40 °C. Experimental results can be summarized that temperature, surface modification, and mixing ratio are effective factors and they influenced the effects of FA amendment on WRC of soils and sands. Some porous surfaces may lead to higher WRC. Building of aggregation can influence water retention capacity. Cellulose modification is positive on increasing WRC of AS and SS.

Soil and Temperature Dependency of Coal Fly Ash Amendment Effect on Water Holding Capacity of Natural Soils

( Shenglei Lin ),( Mengzhu Song ),( Fumitake Takahashi ) 한국폐기물자원순환학회(구 한국폐기물학회) 2015 한국폐기물자원순환학회 3RINCs초록집 Vol.2015 No.-

Coal fly ash (FA), one of the major by-products from coal-fired power generation, was largely generated all over the world. The focusing point in this research is utilizing FA as water holding agency for soils to stop serious desertification problem. Thus, raw FA and Calcium Phosphate, Chitosan, Sodium Alginate, Guanidine Hydrochloride treated or mixing treated FA are tested on their effect on WHC of two kinds of natural soils under 40 ºC and natural condition (N.C.), in order to find out facts that determine WHC most. WHC experiments and data processing are carried out to compare the mixing ratio dependency, soil type dependency, temperature dependency and treatment dependency of FA/treated FA. According to the results, lower use level of phosphate or pure organic treatment will increase WHC of FA, but higher use level of phosphate or lower use level of organic treatment with more phosphate will decrease WHC of FA. Mixing ratio dependency is found in Chi-Bas treated FA amended soils.

P/Ca Ratio Dependency of Sand Water Holding Capacity amended by Apatite-synthesized Coal Fly Ash

( Shenglei Lin ),( Mengzhu Song ),( Fumitake Takahashi ) 한국폐기물자원순환학회(구 한국폐기물학회) 2016 한국폐기물자원순환학회 춘계학술발표논문집 Vol.2016 No.-

With the increase of coal-fired power generation all over the world, huge amount of coal fly ash (FA) are produced. Discharging of FA is becoming a serious environment problem, especially in coal consuming countries like China, India, America and Australia, etc. A high efficient way to recycle FA is required. In this research FA was tested as sand water holding agent from the viewpoint of anti-desertification. Desertification has become a serious social problem in these years and an effective way to stop desertification is required. In this study effect of amending FA on water holding capacity (WHC) of sand was analyzed. Raw and surface modified FA was tested. Materials used in this study are silica sand (SS), river sand (RS) and coal fly ash. For FA modification, apatite synthesis was conducted on FA surface and P/Ca ratios were set to 3, 7.12, 11.67 and 16. WHC of sand, raw/modified FA, and sands amended with raw/modified FA were measured by drying experiments. 7.5 g of pure water was added to 17.5 g of dried sample to adjust initial water content as 30 wt%. FA amending ratios are 10 wt%? 20 wt% and 30 wt%. Moistened samples were dried under natural condition (around 20 °C) or dried isothermally in an oven at 40 °C for 12 hours. The weights of moistened samples were measured at 1 hour intervals to monitor water retention in the sample. According to drying experimental data, water retention curves were drawn, which are weight-based relative percentages of remained water in the sample at different drying times. WHC amount (h) is calculated from area of water retention curves. WHCs were compared to figure out effect of FA amendment on WHC of sands and P/Ca ratio dependency of sand WHC. Statistical analysis was conducted for all data. According to experimental results at room temperature, WHC of SS, RS, raw FA, and modified FA with P/Ca ratio of 7.12 and 11.67 are almost the same while WHC of modified FA with P/Ca ratio of 3 and 16 are higher. At 40 OC, WHC of samples varied a lot. However, WHC of modified FA with P/Ca ratio of 11.67 kept the same WHC with that at room temperature. As an example of experimental results, Figure 1 shows the effect of modified FA amendment with P/Ca ratio of 3 to 11.67 on WHC of SS at 40 OC. When modified FA with P/Ca ratio of 3 was mixed into SS, WHC was increased to the same level regardless of mixing ratio. On the other hand, mixing modified FA with P/Ca ratio of 11.67 into SS showed almost no effect on WHC of SS. Experimental results can be summarized that temperature, surface modification, and mixing ratio are effective factors and they influenced the effects of FA amendment on WHC of SS and RS. Raw FA showed negative effect and most of apatite synthesized FA showed positive effect to increase WHC of SS. However, almost no effect of modified FA with P/Ca ratio of 7.16 on WHC of SS and of FA amendment on WHC of RS was found, respectively.

Physical performances of a potassium-based geopolymer derived from coal fly ash

( Patcharanat Kaewmee ),( Mengzhu Song ),( Giun Jo ),( Fumitake Takahashi ) 한국폐기물자원순환학회(구 한국폐기물학회) 2019 한국폐기물자원순환학회 심포지움 Vol.2019 No.1

Coal fly ash, a residue from coal burning, can be directly used as an alternative source to create many useful products, applying for soil improvement, concrete replacement, catalysts, environmental pollution protection, and so on. Recently, many researches have been geared into geopolymer productions using many alkali solutions as activators. The application of sodium-based fly ash geopolymers are widely reported previously, rather than the use of the potassium-based fly ash geopolymers. To enlarge the ability of potassium-based geopolymer, potassium silicate and potassium hydroxide were employed for the geopolymer fabrication in this study. Therefore, to explore the optimum synthesis condition regarding the geopolymers’ qualities, different alkali activator ratio was investigated. The ratios of potassium silicate to potassium hydroxide solution were varied to 3.5: 1, 1.5: 1, 0.5: 1, and 0.3: 1, respectively. Results show that the obtained geopolymers were found to be highly interconnected porous macrostructure. The density of the geopolymers decreased with the decreasing of silicate soluble content. Similarly, the decrease of silicate content also affected the durability of the geopolymers. However, the obtained geopolymer exhibited high mechanical durability index at about 93% for the geopolymer at ratio of 0.3: 1. In addition, the results suggested that the highly porous potassium-based geopolymers can be further applied in many applications.

Fly ash-based porous geopolymer: Synthesis and study on methylene blue removal

( Patcharanat Kaewmee ),( Reza Khoshbouy ),( Mengzhu Song ),( Giun Jo ),( Fumitake Takahashi ) 한국폐기물자원순환학회(구 한국폐기물학회) 2018 한국폐기물자원순환학회 심포지움 Vol.2018 No.1

Thermal energy production generates a large amount of by-product fly ash after coal burning. Coal fly ash contains many toxic metals and might cause a lung disease and respirator problem in human. While most of produced fly ash is directly disposed by landfilling, it has become an environmental concern. To achieve environmental and economic benefits, recycling of this waste material and converting it into usable and valuable materials are necessary. Generally, fly ash mainly contains alumino-silicate component which can be used as an alternative source to form geopolymer. Fly ash-based geopolymer has been focused on many applications such as cement and concrete replacement as well as toxic metal removal. Moreover, geopolymer production emits less carbon dioxide and consumes less energy requirement compared to ordinary Portland cement manufacturing process. Geopolymer can be easily synthesized by reacting alumino-silicate components in raw solid material with an alkali activator through geopolymerization reaction at elevated temperatures (<100°C). Geopolymerization introduces a high potential polymeric Si-O-Al framework on the geopolymer structure. However, most of geopolymer have dense structure which limit the water permeability and also have low porosity which affects the adsorption ability. In term of environmental cleanup, a large surface area on adsorbent structure is extremely important. In this study, class F fly ash is used as a raw material for fabrication of high porous geopolymer and tested as a methylene blue (MB) adsorbent. To fabricate the porous geopolymer, the raw fly ash was reacted with a mixtures of potassium silicate and potassium hydroxide which used as an alkali solution for this study. The geopolymerization reaction occurs at about 80 °C and the slurries of fly ash and alkali activator were obtained. Subsequently, the pore forming agent was added into the slurries at room temperature in order to form the porous structure on the geopolymer surfaces. The reacted slurries were cured at 80 °C to achieve the geopolymer with solid structure. The synthesized fly ash-based geopolymer after geopolymerization process exhibits highly pore structure with various pore sizes (see Figure 1). The morphologies of geopolymers were analyzed using a scanning electron microscopy. It shows highly porous microstructure of synthesized geopolymer. Obviously, an increase of pore forming agent encourages higher pore structures on the geopolymer surface. This pore-forming agent plays an important role in sponge-like porosity creation and increases the surface area. In addition, the fly ash-based geopolymers present a great efficiency for methylene blue removal. This work demonstrates the fly ash-based geopolymer is a promising adsorbent in dye removal and can be further used to other heavy metals removal application.