Ash Loading Research Articles

Experimental study of lubricant-derived ash effects on diesel particulate filter performance

Diesel particulate filters are indispensable for diesel engines to meet the increasingly stringent emission regulations. A large amount of ash would accumulate in the diesel particulate filter over time, which would significantly affect the diesel particulate filter performance. In this work, the lubricant-derived ash effects on diesel particulate filter pressure drop, diesel particulate filter filtration performance, diesel particulate filter temperature field during active regeneration, and diesel particulate filter downstream emissions during active regeneration were studied on an engine test bench. The test results show that the ash accumulated in the diesel particulate filter would decrease the diesel particulate filter pressure drop due to the “membrane effect” when the diesel particulate filter ash loading is lower than about 10 g/L, beyond which the diesel particulate filter pressure drop would be increased due to the reduction of diesel particulate filter effective volume. The ash loaded in the diesel particulate filter could significantly improve the diesel particulate filter filtration efficiency because it would fill the pores of diesel particulate filter wall. The diesel particulate filter peak temperature during active regeneration is consistent with the diesel particulate filter initial actual soot loading density prior to regeneration at various diesel particulate filter ash loading levels, while the diesel particulate filter maximum temperature gradient would increase with the diesel particulate filter ash loading increase, whether the diesel particulate filter is regenerated at the same soot loading level or the same diesel particulate filter pressure drop level. The ash accumulation in the diesel particulate filter shows little effects on diesel particulate filter downstream CO, total hydrocarbons, N2O emissions, and NO2/NO x ratio during active regeneration. However, a small amount of SO2 emissions was observed when the diesel particulate filter ash loading is higher than 10 g/L. The ash accumulated in the diesel particulate filter would increase the diesel particulate filter downstream sub-23 nm particle emissions but decrease larger particle emissions during active regeneration.

Analysis of the Emission Conversion Performance of Gasoline Particulate Filters Over Lifetime

<div class="section abstract"><div class="htmlview paragraph">Gasoline particulate filters (GPF) recently entered the market, and are already regarded a state-of-the-art solution for gasoline exhaust aftertreatment systems to enable EU6d-TEMP fulfilment and beyond. Especially for coated GPF applications, the prognosis of the emission conversion performance over lifetime poses an ambitious challenge, which significantly influences future catalyst diagnosis calibrations. The paper presents key-findings for the different GPF application variants. In the first part, experimental GPF ash loading results are presented. Ash accumulates as thin wall layers and short plugs, but does not penetrate into the wall. However, it suppresses deep bed filtration of soot, initially decreasing the soot-loaded backpressure. For the emission calibration, the non-linear backpressure development complicates the soot load monitoring, eventually leading to compromises between high safety against soot overloading and a low number of active regenerations. In the second part, a relevant share of ash deposits inside three-way catalysts (TWC) is depicted. In an experiment, the oxygen storage capacity (OSC) of a three-way catalyst was significantly lowered by ash, while a coated GPF showed little effects. A subsequent OSC regeneration of the TWC showed that the OSC drop is not necessarily permanent, reducing the selectivity between full useful life and borderline catalysts.</div></div>

Integrating the Bottom Ash Residue from Biomass Power Generation into Anaerobic Digestion To Improve Biogas Production from Lignocellulosic Biomass

The bottom ash residue derived from biomass power generation was characterized by alkalinity and contained about 35 mineral elements, which offered a possibility to improve anaerobic digestion of lignocellulose biomass via providing mineral nutrients for microorganisms and alkali conditions for pretreatment. Technically, bottom ash was mixed with distilled water to prepare the extracting solution for this investigation. To check the function as a nutrient provider of bottom ash, the increased bottom ash loading from 0.37 to 2.96% was employed to achieve the extracting solutions with different concentrations of mineral elements. Rice straw was mixed with these extracting solutions for 7 days and then employed for the anaerobic digestion in batch. Results indicated that 314.38 mL/g of total solid biogas was achieved by 0.37% bottom ash, which was 21.2 and 15.8% higher than that of the blank and 0.12% NaOH (equivalent alkalinity of 0.37% bottom ash), respectively, proving that bottom ash substantially functi...

Design of a Novel Gasoline Particulate Filter Aging Method

Gasoline particulate filters (GPF) recently entered the market and are already regarded as state-of-the-art for gasoline exhaust aftertreatment systems to enable EU6d-TEMP fulfillment and beyond. Due to its rapid market introduction, the field of GPF lifetime evaluation is still open for research. In this context, the paper describes the advantages of a method for accelerated investigation of filter ash loading during the development of particulate filters. The central task is the simulation of real-world lubrication oil consumption and combustion, which is the major source of ash in the exhaust gases. For that purpose, a burner test bench designed for catalyst aging was additionally equipped with an oil injection unit. The injection unit enables control of the oil volume and the droplet sizes as precursors for the ash particulates. The results obtained with the new filter aging method are compared with data from vehicle endurance runs and with burner test investigations in which the fuel is doped with oil. The latter method is currently considered as the state-of-the-art method for accelerated ash generation. The new method proofed to be vehicle-equivalent in terms of ash-induced backpressure, filtration efficiency, wall ash layer formation, and wall/plug ash ratio. In this context, it turned out that it is important not to atomize the oil droplets too far, since smallest particulates accumulate mainly at the walls and cause unrealistically high backpressures. Furthermore, the ash loading process should include different mass flows in order to achieve stable backpressure results.

Characteristic properties of ceramic membrane derived from fly ash with different loadings and sintering temperature

Nowadays, ceramic membrane developed from wastes has gained attention, especially towards water separation applications. With abundant and high silica content of fly ash, low cost ceramic membrane was successfully prepared via phase inversion and sintering technique. Prior to both phase inversion and sintering process, ceramic suspension was prepared at different loadings, ranging from 40wt% to 50 wt% fly ash and subsequently sintered at temperature ranging from 1150°C to 1350°C. By varying fly ash content and sintering temperature, the morphology, mechanical strength and phase transformation characteristics of the prepared membrane were affected. The characterisation of prepared membrane were investigated by using scanning electron microscopy, three-point bending test, and X-ray diffraction (XRD). The mechanical strength of the membrane increased with increasing fly ash loading (up to 45 %), however too much fly ash loading resulted in decrease of its mechanical strength probably due the presence of unburnt at higher fly ash contents. This unburnt carbon contributed to the vacant space during sintering process and had the tendency to increase formation of pores, simultaneously reduced its mechanical strength. In addition, the SEM results also illustrated a cross-sectional image of the membrane which had become more elastic with increasing fly ash loading and denser as sintering temperature gradually increased. In addition, increasing the fly ash loading likely discouraged the formation of desired finger-like structure. The XRD results however showed continuous presence of mullite with the increasing sintering temperature which contributed higher mechanical strength. The preliminary performance tests indicated that the optimum conditions to produce hollow fibre ceramic membrane from fly ash were at 45 wt % fly ash loading sintered at 1350°C and has a pure water flux of 131 L/m2h.

Impacts of rice husk ash filler loading on curing, morphological characteristics and tensile properties of natural rubber/ethylene propylene rubber blends

Rice husk is an agro industrial waste that potentially used in biomaterial application. It contains high silica that could be utilized as a reinforcing filler to substitute commercially precipitated silica or other commercial fillers in rubber compounding application. This research studied the effect of rice husk ash (RHA) loading as reinforcing filler in Natural Rubber/Ethylene Propylene rubber (NR/EPR) blends. The effects were observed by applying 40, 50, 60, 70 phr of RHA filler in the rubber compounding for NR (100) and also for blending NR/EPR (70:30). The rubber compounding and vulcanization for the rubber compounding was conducted according to the ASTM D-3182. The results showed that RHA were successfully prepared and introduced as a new alternative filler for rubber industrial application. Based on the curing characteristics, the RHA loading influence slightly ts2, t90, ML, MH and cross link density on the NR blending with and without EPR addition. At the same RHA composition, the torque and cross link density of NR-EPR blending were much higher compared to only NR. RHA loading on NR with and without EPR composites caused a slight decreasing on tensile strength, elongation at break, and compression set. Conversely, the hardness of those composites tended to increase due to the RHA addition. The SEM micrographs provided additional evidences on the poor tensile properties as well as the matrix tearing and voids due to EPR addition into NR composites. To sum up, RHA may be used as an alternative filler for NR composites along with the EPR addition in order to improve compression set and hardness properties without losing tensile properties of the composites.

Effect of CaO and biomass ash on catalytic hydrogasification behavior of coal char

Three rich-alkalis biomasses ashes, wheat straw ash (WSA), sea grape ash (SGA) and Ixeris Chinese ash (ICA) and calcium-based additives, were applied in char hydrogasification. Hydrogasification behavior of coal and biomass ash and saturated loading and loading methods of calcium-based additives were investigated. The loading calcium-based additives has affected on the methane release curves of SFC hydrogasification. The total amount of gaseous products and the CH4 yield were obviously improved with the increase of the CaO loading. Hydrogasification of SF char with the 6% calcium-based loading presented the highest methane yield. SFC hydrogasification was divided into two stages according to the methane release rate curve of the calcium-based additives-loaded samples hydrogasification. The carbon and hydrogen reaction occurred in the second stage of coal hydrogasification. The calcium-based additives have effects on catalytic performance of three rich-alkalis biomass ashes for hydrogasification characteristics of Shenfu coal char. Loading methods of calcium-based additives and component of biomass ashes affected on the total CH4 yield and the total amount of gaseous products of samples. Calcium-based additives emerged obviously synergistic reaction with WSA or SGA during char hydrogasification. Calcium-based additives reacted with Si of biomass ashes and produce more stable calcium silicate in the early stage of reaction. The promotion of biomass ashes on char hydrogasification mainly was attributed to the fixation of Si and Cl by CaO.

Fuels, vegetation, and prescribed fire dynamics influence ash production and characteristics in a diverse landscape under active pine barrens restoration

BackgroundAn important consequence of wildland fire is the production of ash, defined as a continuum of mineral to charred organic residues formed by the burning of wildland fuels. Ash may impact soil health depending on its elemental composition and other factors, which are influenced by fuel quantity and quality, and by combustion completeness. To investigate how ash properties relate to variation in fuels and fire, we collected and analyzed ash samples following prescribed fires in a pine barrens landscape spanning grassland, shrubland, conifer woodland, and deciduous forest. At some plots, mechanical brush cutting was applied, and woody fuels were added or removed to experimentally manipulate fuel loads.ResultsAsh load averaged 2 Mg ha−1, or approximately 12.5% of fuel consumption, and was positively related to maximum temperatures estimated by temperature-sensitive paint tags. Ash load also increased in cut brush and fuel addition treatments. Fuel consumption in grasslands, estimated from maximum paint tag temperatures by calibration, was increased by woody fuel addition. Total nutrient stocks in ash was greatest at conifer sites (i.e., nitrogen, N; phosphorus, P; potassium, K; magnesium, Mg; and iron, Fe) and lowest at grassland sites (P; K; calcium, Ca; Mg; and manganese, Mn). Concentrations of leachable nutrients in ash were high for cations Ca (>20 g kg−1), K (>4 g kg−1), and Mg (>5 g kg−1), which resulted in high ash pH (mean ± standard error = 8.4 ± 0.1). Leachable cations were positively related to total ash cation concentrations, but leachable metal concentrations (Fe; Mn; copper, Cu) were low despite their high content in ash.ConclusionsWe observed differences in ash production and composition that corresponded to variation in vegetation cover, fuel loads, and paint tag temperatures. High concentrations of leachable cations in ash suggested that repeated prescribed fire may act to decrease cation availability in soils if cations are leached through sandy soils over time. In the case of pine barrens, prescribed fires, which decrease carbon (C) stocks while producing high concentrations of leachable nutrients in ash, may contribute to decreased soil nutrient stocks, and more limited tree growth, thus helping to maintain and restore critically endangered barrens ecosystems.

Characterization of soot deposition and oxidation process on catalytic diesel particulate filter with ash loading through an optimized visualized method

The purpose of study is to investigate the structure of soot layer and evolutionary mechanisms of its deposition/regeneration process when applying five ash loadings in CDPF. The mechanisms can be used to reveal the principle of dual-layer filtration technology and lay the proper foundation for making advanced regeneration strategies to save energy and improve efficiency. The characterization of soot layer structure was analyzed by 2-D laser displacement sensor, pressure sensor and scanning electron microscope (SEM). The deposition process could be divided into four stages. The shift value of particle layer thickness to start the last stage was about 20 µm. With the ash amounts increasing, the initial pressure drops increased from 1260 Pa to 4550 Pa and the time-consuming in the first three deposition stages reduced from 250 s to 0 s. The mechanism of 2 g/L ash condition was similar to the dual-layer technology. The regeneration process could be divided into three stages. The irregular soot layer scallops were found in the middle of the 2nd regeneration stage. The “back diffusion” of micro-concentration oxygen molecules caused by catalyst could reduce the beginning temperature from 525 °C to 500 °C. With the ash amounts increasing from 0 g/L to 8 g/L, the duration time of II-regeneration stage gradually reduced from 3000 s to 0 s. The ash particles could act as oxygen carrier and have a catalytic effect on soot layer. The ash layer could absorb more thermal energy and have higher heat storage capacity.

3D pore analysis of gasoline particulate filters using X-ray tomography: impact of coating and ash loading

Since particulate emissions control technologies are dependent on filtration technologies, development of porous materials with optimized pore structures is crucial to improve filtration efficiency and pressure drop across filters. Despite increasing attention to 3D measurements of porous materials, there are few reports of pore structure investigations of diesel/gasoline particulate filters (D/GPFs) using 3D visualization techniques. In this work, GPF 3D pore structures were examined using X-ray tomography (XRT) to identify the impacts of catalyst coating or ash loading. Voxel resolution of 2.93 µm made it impossible to distinguish coating or ash materials from the cordierite substrate or to recognize smaller pores than the voxel resolution. However, pores up to 200 µm, which are responsible for the most pore volume, were successfully analyzed. Coating and ash loading resulted in lowering average pore diameter, total porosity, and open porosity, as the peak density of pore diameter at 60 µm decreased, while pores below 20 µm increased. Also, the visualized closed pores, which were homogeneously distributed throughout the bare filter, tended to get larger from inlet to outlet sides and more likely to be on the surface inlet due to coating and ash loading, indicating gas pathways originally existing in open pores were blocked due to coating and ash loading, leading to increased pressure drop. The ash impact was found to be more noticeable on mid and back positions than on front position. In addition, the investigation of areal porosity along the direction of gas flow suggested that while ash penetration could reach the outlet side as noted from increased closed pore population, most ash particles would be contained up to 150 µm. The 2D crosscut microscopic analysis that requires destructive procedures with the limited examination area could provide underestimation of ash penetration, whereas the 3D XRT analysis seems to provide more accurate information of pore structure changes due to ash loading at different locations.

A microwave-activated coal fly ash catalyst for the oxidative elimination of organic pollutants in a Fenton-like process.

Raw coal fly ash was first activated by microwave irradiation to promote its catalytic potential and then used as a Fenton-like catalyst to treat polyacrylamide-contaminated wastewater. The optimal activation conditions of the raw coal fly ash (microwave power = 700 W, irradiation time = 10 min, mixing speed = 120 rpm, and raw coal fly ash loading = 20 g L−1) were determined by the orthogonal test. The significance of each effective parameter follows the order: raw coal fly ash loading > microwave power > irradiation time > mixing speed. Microwave irradiation can change the surface morphology and remarkably increase the specific surface area and pore volume. More than 75% of the TOC in the polyacrylamide-contaminated wastewater can be removed under the optimized treatment conditions ([H2O2] = 12 mg L−1, catalyst loading = 10 g L−1, [polyacrylamide] = 200 mg L−1, T = 313 K). The kinetic study shows that the variation in the catalyst loading and the polyacrylamide concentration can change the degradation path of the polyacrylamide, whereas the variation in the H2O2 dosage can accelerate the degradation of polyacrylamide. The Fenton-like process studied herein has a wider optimal pH range (2–5) than that of the classic Fenton process (3). The catalyst has weak catalytic capacity but better catalytic persistence than that of Fe2+. During the five runs of the catalyst, some heavy metallic and toxic elements (Fe, Al, Ti, Cr, Mn, etc.) can be detected but under the limits of the GB8978-1996 standard. Leaching can weaken the catalytic capacity (i.e., stability) of the catalyst. The catalytic process is caused by the synergism of multiple metals and consists of heterogeneous and homogeneous processes.

Seismic Data, Photographic Images and Physical Modeling of Volcanic Plumes as a Tool for Monitoring the Activity of Nevado del Ruiz Volcano, Colombia

Quantification of volcanic plume parameters is a fundamental task to know the behavior of an active volcano. Volcanic plume mass, flow rate and ash injection were determined from integration of scaling laws of several volcanic plume models, seismic data, and photographic images for the period 1985–2017 for Nevado del Ruiz Volcano (NRV), Colombia, with the aim to quantify the ash emitted volume during this period and to establish a relationship between seismicity and those volcanic plume parameters. The results show a decrease of ~ two orders of magnitude in the volume of ash plumes from the November 13, 1985 eruption (0.12 km3) to the September 1, 1989 eruption (1.43x10-3 km3). This pattern is preserved for the June 30, 2012 eruption and 2015-2017 eruptive cycle, with volumes five times smaller than in 1989. The results also show a correlation between radiated seismic energy (RSE) of the volcanic tremor and ash load for higher (>1 km) and longer-duration (>240 s) plumes. It was possible to calculate a minimum value of ash load based on radiated seismic energy (RSE) release and reduced displacement (RD) of volcanic tremor signal associated with the eruption, which could be used as a monitoring tool. Moreover, for the period 2015-2017 changes in volume of ash plume were correlated with changes in reduced displacement (RD, a way of normalizing volcanic tremor to a common scale) and RSE, associated with different stages of volcanic activity. The continuous decreasing of ash plume volumes from 1985 to 2017 suggests a same volcanic cycle almost ending. On the other hand, the evidence of new magmatic input in 2007 might suggest that a new volcanic cycle started on that date and still in process of magma ascending. Probably in the next future surface evidence of the new cycle can be observed at NRV or other volcanoes around it.

Investigating the impact of an Al-Si additive on the resistivity of biomass ashes

Ash resistivity is an important factor in the collection efficiency of electrostatic precipitators (ESPs). There is good experience in the industry regarding resistivity of coal fly ash and well-established models for its prediction based on coal ash composition. The same is not true for biomass ash and this paper reports much-needed data for three different biomass types. Coal pulverised fuel ash (PFA), can be used as an aluminosilicate additive to mitigate biomass ash deposition issues. The effects of PFA additive on the resistivity of biomass ashes is also reported here. Biomass ash resistivity is an order of magnitude lower than that of typical coal ashes, and thus re-entrainment of particles in ESPs may become an operational issue, exacerbated by the presence of moisture and sulphur. PFA additive can increase the resistivity, but also leads to higher ash loading. Regression analysis indicates that potassium in biomass ash impacts significantly upon resistivity, contrary to previous studies. Various existing resistivity models were tested for predicting biomass ash resistivity; they produced significant overestimates when compared to experimental results due to omission of potassium as a component of the ash. Modifications to existing models or new models are required to predict resistivity of biomass ashes, and the data reported here will be important for developing such a model.

Fragility Assessment of Vinyl Greenhouses and Livestock Sheds Subjected to Volcanic Ash Fall Hazards

In this study, fragility functions are developed to estimate expected volcanic ash damage to vinyl greenhouses and livestock sheds among common agricultural facilities in South Korea. The fragility functions are derived through the FOSM (first-order second-moment) analytical approach based on the thickness distribution of volcanic ash observed in the 1980 eruption of Mt. Saint Helens in the USA and on agricultural facility codes and specifications in South Korea. In this study, the volcanic ash fragility functions evaluated represent the conditional probability of failure of vinyl greenhouses and livestock sheds over the full range of volcanic ash loads. For the evaluation, 4 types (i.e., automated, single span, tree crop, and double span types) of multi-hazard resisting vinyl greenhouses and 3 types (i.e., standard, coastal, and mountain types) of livestock sheds conventionally utilized in South Korea are considered. All volcanic ash fragility functions estimated in this study are fitted using parameters of the lognormal CDF (cumulative distribution function), and the obtained parameters are compiled into a database for use in the future. The volcanic ash fragility functions developed in this study are intended to be used to evaluate potential risks and losses from volcanic eruptions around the Korean Peninsula.

Mechanical Properties and Thermal Conductivity of Coal Ash-Recycled High-Density Polyethylene Composite

In this study, coal ash/recycled plastic composite material was fabricated with post-consumer high-density polyethylene (HDPE) and coal ash particles. The main idea of using coal ash, since it is also a waste product, as reinforcing filler in recycled HDPE is to reduce the cost, develop lightweight and produce environmental-friendly materials. Coal ash/recycled plastic composite have been used in significant applications as construction materials including flooring, landscaping, fencing, railing window framing and roof tiles. Effect of coal ash loading on the mechanical properties and thermal conductivity of coal ash/recycled HDPE composite were determined. It is expected to use waste materials in new field by getting novel composite materials with developed mechanical properties. It was found that coal ash filler indicated significant improvement on the mechanical properties of composites. The results show that the impact decreased tremendously from 57.32 to 15.8[Formula: see text]kJ/m2 with only 30[Formula: see text]wt.% loading of coal ash. The filler increases the elasticity of the material and reduces its ability to absorb deformation energy.

Industrially viable technique for the preparation of HDPE/fly ash composites at high loading: Thermal, mechanical, and rheological interpretations

ABSTRACTThis article describes an industrially viable melt blending approach for the preparation of high‐density polyethylene (HDPE)/fly ash composites having high loading of fly ash (FA) (up to 25 wt %). In this approach, solvent was used to enhance the mixing of FA in HDPE matrix. FA coated on the outer surface of HDPE granules using solvent is an economical technique for the incorporation of high loading of FA using conventional twin screw extruder. Herein, the effect of HDPE reinforced with FA on thermal, rheological, and mechanical properties has been investigated. Incorporation of FA in HDPE matrix resulted in higher storage modulus (E′), loss modulus (E″), and complex viscosity (η*) as compared to neat polymer. Tensile and flexural moduli were also found to increase (∼47% and ∼66%, respectively) with the addition of FA (25 wt %). However, the elongation at break of HDPE reduced as the rigid spherical FA particles do not undergo elongation. The dispersion of FA within the polymer matrix and interaction of FA with HDPE were investigated using scanning electron microscopy. Rheological and mechanical properties of the composites were also correlated with the morphology. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45995.

Morphological, mechanical and thermo-kinetic characterization of coal ash incorporated high performance PEO/PMMA thin film electrolyte composites

In the present work indigenous coal ash of Pakistan was used to prepare polymeric nanocomposites with Poly (ethylene oxide) (PEO)/Poly (methyl methacrylate) (PMMA)/lithium perchlorate (LiClO4). The coal ash was first characterized by various advanced spectroscopic techniques. The coal ash loading into the polymeric blend composites was considered by Thermo gravimetric/differential thermal analysis (TG/DTA), universal testing machine (UTM) and scanning electron microscopy (SEM)/energy dispersive x-rays (EDX) analysis. From TG/DTA data detailed kinetic analysis was performed. By applying various kinetic models, a range of kinetic parameters like ▵E, ▵G, ▵H, ▵S and A were successfully calculated for the first time for the studied system. Based upon aforementioned characterization it was established that coal ash incorporation into the polymeric blend composites improves its thermal and mechanical performance.

Use of cement-chelated, solidified, municipal solid waste incinerator (MSWI) fly ash for pavement material: mechanical and environmental evaluations

As a by-product from the incineration of municipal solid waste (MSW), fly ash usually contains mobile heavy metals that may engender severe pollution when reused. In this study, fly ash was solidified with cement and a chelating agent to immobilize these polluting elements. The possibility of using the solidified fly ash for pavement materials was also assessed through mechanical and environmental perspectives. According to the results, the strength of solidified fly ash was found proportional to both the cement/fly ash ratio and curing time. This indicated that the increase of fly ash loading reduced the concentration of products from cement hydration, and thus destroyed the structure of the products of hydration. With the increase of freeze–thaw cycles, the compressive strength of cement-stabilized fly ash decreased between days 7 and 14, and then increased between days 14 and 28. Subsequently, the finite element analysis showed that placing the solidified fly ash layer as a pavement material between an unbound base course and subgrade was beneficial to prolong fatigue life and reduce rutting distress of asphalt pavements. Finally, leachability of metals from the mixtures was tested, which showed that leaching concentration decreased as the cement/ash ratio, curing time, and chelating agent content increased.

Effect of Commercial SiO2 and SiO2 from rice husk ash loading on biodegradation of Poly (lactic acid) and crosslinked Poly (lactic acid)

In this work, biodegradation behavior of poly (lactic acid) (PLA) and crosslinked PLA filled with two types of SiO2, precipitated SiO2 (commercial SiO2) and SiO2 from rice husk ash, were studied. Rice husks were first treated with 2 molar hydrochloric acid (HCl) to produce high purity SiO2, before burnt in a furnace at 800°C for 6 hours. All components were melted bending by an internal mixer then hot pressed using compression molder to form tested specimens. FTIR spectra of SiO2 and PLA samples were investigated. The results showed the lack of silanol group (Si-OH) of rice husk ash after steric acid surface modification, while the addition of particles can affect the crosslinking of the PLA. For biodegradation test by evaluating total amount of carbon dioxide (CO2) evolved during 60 days incubation at a controlled temperature of 58±2°C, the results showed that the biodegradation of crosslinked PLA occurred slower than the neat PLA. However, SiO2 incorporation enhanced the degree of biodegradation In particular, introducing commercial SiO2 in PLA and crosslinked PLA tended to clearly increase the degree of biodegradation as a consequence of the more accelerated hydrolysis degradation.

Dynamic Changes of Disinfection Byproduct Precursors following Exposures of Microcystis aeruginosa to Wildfire Ash Solutions.

Wildfires can elevate dissolved organic matter (DOM) levels due to ash input and algal growth in source waters, and consequently impacting disinfection byproduct (DBP) formation in finished water; however, it remains unclear how quality and quantity of overall allochthonous and autochthonous DOM as well as associated DBP formation are changed during an entire algal life cycle. Microcystis aeruginosa was cultured in the medium containing low and high concentrations [10% and 65% (v/v)] of black and white ash water extracts (BE and WE) to study dynamic changes of carbonaceous, nitrogenous, and oxygenated DBP precursors during algal growth. DOM was characterized by absorption and fluorescence spectroscopy and chlorination/chloramination-based DBP formation experiments. Throughout the entire experiment, C-DBP precursors in the control ranged from 2.41 to 3.09 mmol/mol-C. In the treatment with 10% BE, the amount of C-DBP precursors decreased from 6.8 to 3.0 mmol/mol-C at initial-exponential phase then increased to 4.2 mmol/mol-C at death phase. The same trend was observed for O-DBP precursors. However, these dynamic changes of C- and O-DBP precursors exhibited opposite patterns in 65% extracts. Similar patterns were also observed in the WE treatments. On the other hand, N-DBP precursors continuously declined in all treatments. These results indicate that postfire ash loading and algal bloom stage may significantly affect DBP formation in source water.