Assessing the health risk of reuse of bottom ash in road paving

Although the reuse of bottom ash has been favored gradually, reflected on regulations and researches, the associated risk is still an issue of great concern. This study quantified the health risks from multimedia transport and multi-pathway exposure to the concerned chemicals as a result of reusing bottom ash in road paving with consideration of various application scenarios. In particular, the using duration of the pavement was taken into consideration because movement of chemicals in the soils and groundwater would affect the subsequent exposure and risk. By using soil and groundwater transport modeling linked to food chain exposure assessment and incorporating the Monte Carlo method, the study identified Cr as the crucial toxicant and ingestion of drinking water and vegetables as the key exposure pathways. Furthermore, control of the using duration of road pavement is an essential factor of management and regulations to minimize the leaching of the hazardous constituents into the groundwater and subsequent contamination of food chain.     

Influence of fly ash aided phytostabilisation of Pb, Cd and Zn highly contaminated soils on Lolium perenne and Trifolium repens metal transfer and physiological stress

Due to anthropogenic activities, large extends of soils are highly contaminated by Metal Trace Element (MTE). Aided phytostabilisation aims to establish a vegetation cover in order to promote in situ immobilisation of trace elements by combining the use of metal-tolerant plants and inexpensive mineral or organic soil amendments. Eight years after Coal Fly Ash (CFA) soil amendment, MTE bioavailability and uptake by two plants, Lolium perenne and Trifolium repens, were evaluated, as some biological markers reflecting physiological stress. Results showed that the two plant species under study were suitable to reduce the mobility and the availability of these elements. Moreover, the plant growth was better on CFA amended MTE-contaminated soils, and the plant sensitivity to MTE-induced physiological stress, as studied through photosynthetic pigment contents and oxidative damage was lower or similar. In conclusion, these results supported the usefulness of aided phytostabilisation of MTE-highly contaminated soils.     

改性粉煤灰与过氧化氢联合作用深度处理皂素生产废水的研究

利用改性粉煤灰与过氧化氢(H2O2)联合的方法对二次处理过的皂素生产废水进行深度处理,研究了pH、改性粉煤灰投加量、H2O2投加量、反应时间对皂素生产废水脱色率和COD去除率的影响,分析了其作用机制.结果表明,试验最佳条件为:pH=6、反应时间60 min、改性粉煤灰投加量10 g/L、H2O2投加量4 mL/L.在最...     

攀钢选钛厂主流程工艺流程优化研究

分析了选钛厂主流程生产现状,针对工艺中存在的问题,根据新设备、新技术在选钛厂的成功实践,提出了优化工艺流程思路,减少了不安全因素和产尘点,以提高主流程重选作业收率,增加选钛厂钛精矿产量.     

Evaluation of sulfate resistance of cement mortars containing black rice husk ash

In this paper, black rice husk ashes (BRHAs), which are agrowastes from an electricity generating power plant and a rice mill, were ground and used as a partial cement replacement. The durability of mortars under sulfate attack including expansion and compressive strength loss were investigated. For parametric study, BRHA were used as a Portland cement Type 1 replacement at the levels of 0%, 10%, 30%, and 50% by weight of binder. The water-to-binder ratios were 0.55 and 0.65. For the durability of mortar exposed to sulfate attack, 5% sodium sulfate (Na₂SO₄) and magnesium sulfate (MgSO₄) solutions were used. As a result, when increasing the percentage replacement of BRHA, the expansion and compressive strength loss of mortar decreased. At the replacement levels of 30% and 50% of BRHA, the expansion of the mortars was less than those mixed with sulfate-resistant cement. However, the expansion of the mortars exposed to Na₂SO₄ was more than those exposed to MgSO₄. Increasing the replacement level of BRHA tends to reduce the compressive strength loss of mortars exposed to Na₂SO₄ attack. In contrary, under MgSO₄ attack, when increasing the replacement level of BRHA, the compressive strength loss increases from 0% to 50% in comparison to Portland cement mortar. Results show that ground BRHA can be applied as a pozzolanic material to concrete and also improve resistance to sodium sulfate attack, but it can impair resistance to magnesium sulfate attack.     

Application of 'waste' wood-shaving bottom ash for adsorption of azo reactive dye

The utilization of wood-shaving bottom ash (WBA) for the removal of Red Reactive 141 (RR141), an azo reactive dye, was investigated. WBA/H(2)O and WBA/H(2)SO(4) were made by treating WBA with water and 0.1M H(2)SO(4), respectively, to increase adsorption capacity. Adsorption of RR141 from reactive dye solution (RDS) and reactive dye wastewater (RDW) by WBA/H(2)O and WBA/H(2)SO(4) involved the BET surface area and pore size diameter. Properties of adsorbents, effect of contact time, initial pH of solution, dissolved metals and elution studies indicated that the decolorisation mechanism involved both chemical adsorption and precipitation with calcium ions. In addition, the WBA/H(2)SO(4) surface might contain sulphate-cation complexes that were specific to enhancing dye adsorption from RDW. The adsorption isotherm had a best fit by the Freundlich model. Freundlich parameters showed that WBA/H(2)O used more heterogeneous surface than WBA/H(2)SO(4) and activated carbon for RDW adsorption. A thermodynamic study indicated that RDW adsorption was an endothermic process. The maximum dye adsorption capacities of WBA/H(2)O, WBA/H(2)SO(4) and activated carbon obtained from a Langmuir model at 30 degrees C were 24.3, 29.9, and 41.5mgl(-1), respectively. In addition, WBA/H(2)O and WBA/H(2)SO(4) could reduce colour and high chemical oxygen demand (COD) of real textile wastewater. According to the difficulty in the elution study, it was an environmentally safe disposal of this waste. Therefore, WBA, a waste from combustion of wood shavings, was suitable to be used as an effective adsorbent for azo reactive dye removal.     

Highly siliceous MCM-48 from rice husk ash for CO2 adsorption

Mesoporous MCM-48 silica was synthesized using a cationic-neutral surfactant mixture as the structure-directing template and rice husk ash (RHA) as the silica source. The MCM-48 samples were characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), N₂ physisorption and SEM. X-ray diffraction pattern of the resulting MCM-48 revealed typical pattern of cubic Ia3d mesophase. BET results showed the MCM-48 to have a surface area of 1024 m²/g and FT-IR revealed a silanol functional group at about 3460 cm⁻¹. Breakthrough experiments in the presence of MCM-48 were also carried out to test the material's CO₂ adsorption capacity. The breakthrough time for CO₂ was found to decrease as the temperature increased from 298 K to 348 K. The steep slopes observed shows the CO₂ adsorption occurred very quickly, with only a minimal mass transfer effect and very fast kinetics. In addition, amine grafted MCM-48, APTS-MCM-48 (RHA), was prepared with the 3-aminopropyltriethoxysilane (APTS) to investigate the effect of amine functional group in CO₂ separation. An order of magnitude higher CO₂ adsorption capacity was obtained in the presence of APTS-MCM-48 (RHA) compared to that with MCM-48 (RHA). These results suggest that MCM-48 synthesized from rice husk ash could be usefully applied for CO₂ removal.     

底灰动态吸附焦化和造纸废水研究

分析了底灰的化学组成、矿物组成和比表面积等基本理化性质;采用动态吸附柱法研究了底灰处理焦化和造纸废水的性能,探讨了进水流量和吸附柱高度对吸附效果的影响.结果表明,底灰不仅有吸附作用,还具有一定的混凝作用;颗粒态有机碳(POC)较易被混凝除去,焦化废水中POC占总有机碳(TOC)的17%,而造纸废水中POC仅占TOC的2.3%,因此底厌对焦化废水COD的去除效果比造纸废水好;底灰对焦化废水色度的去除率要高于COD;接近吸附饱和时,底灰对造纸废水OM275的去除率仍有约27%,说明造纸废水中苯环类物质相比于其他有机物较易被去除.     

自然堆存下的飞灰污染物浸出毒性研究

测定了飞灰的主要组成成分和重金属元素含量。生活垃圾焚烧飞灰在2年期的自然堆存下,通过分析不同时期污染物浸出特性,以研究飞灰污染物自然老化特征。结果表明：飞灰的主要组成元素有Ca、Si、Al、S、K、Na、Fe、Mg和Cl等,其重金属元素含量大约占1%。飞灰自然老化后,Pb 、Zn 、Cr^6＋、Hg和氰化物的迁移性大大降低;Cu 、As和Cd变化不明显,Cr的浸出略有增加;飞灰中的重金属元素在低pH下仍不具有长期稳定性,因而具有较大的环境风险。     

Continuous CO2 capture and MSWI fly ash stabilization, utilizing novel dynamic equipment

Novel dynamic equipment with gas in and out continuously was developed to study the capture capacity of CO₂. Municipal solid waste incineration (MSWI) fly ash has a high capture rate of CO₂ in CO₂-rich gas. Fly ash can sequester pure CO₂ rapidly, and its capacity is 16.3 g CO₂/100 g fly ash with no water added and 21.4 g CO₂/100 g fly ash with 20% water added. For simulated incineration gas containing 12% CO₂, the capture rate decreased and the capacity was 13.2 g CO₂/100 g fly ash with no water added and 18.5 g CO₂/100 g fly ash with 20% water added. After accelerated carbonation, the C and O contents increased, indicating CO₂ capture in the fly ash; CO₂ combines with Ca(OH)₂ to form CaCO₃, which increased the CaCO₃ content from 12.5 to 54.3%. The leaching of Pb markedly decreased from 24.48 to 0.111 mg/L.