Hot-mix asphalt pavement recycling is widely practiced for its economic and environmental benefits. Existing studies are mainly focused on the engineering properties of reclaimed asphalt pavement (RAP) materials, without considering their impacts on the generated asphalt fumes—a widely recognized environmental hazard. The effects of using RAP on asphalt fumes are systematically studied in this research. Asphalt binders from different sources were used to create RAP materials in three aging conditions. Asphalt fumes were generated and collected from non-aged asphalt materials as well as RAP materials, followed by gravimetric and chemical analysis of the collected asphalt fumes. RAP materials were found to generate greater amount of particulates in asphalt fumes as compared with non-aged ones. RAP materials are also associated with increase in the types and concentrations of polycyclic aromatic hydrocarbons (PAHs) in asphalt fumes, especially those PAHs with more than three aromatic rings. PAHs increase in asphalt fumes is particularly noticeable for RAP created in the natural aging condition. It is reasonable to conclude that asphalt fumes generated from RAP become more hazardous, hence deserving more attention from researchers and practitioners. The mechanisms of the increase in PAHs are discussed, in addition to field exposure studies and mitigation measures.

Introduction

The majority of paved roads around the world are surfaced with hot-mix asphalt (HMA) pavements (Mallick et al., 2017), which are also widely used for the construction of airport runways, parking lots, and other facilities. It is estimated that about 1.6 trillion metric tons of asphalt mixtures are produced annually for the construction, rehabilitation, and maintenance of the paved civil infrastructures (NAPA and EAPA, 2011). The life expectancies of HMA pavements range from a few years to several decades. At the end of their service lives, HMA pavements need to be demolished, creating a large amount of wastes. In the United States alone, for instance, about 100 million tons of asphalt pavements are milled off annually in road resurfacing and widening (MAPA, 2019). The demolished pavements, however, still contain valuable aggregate and asphalt binder. If unattended, they form a significant source of inert solid wastes. Therefore, asphalt pavement recycling has become a common practice for cost saving and environmental conservation (Alam et al., 2010; Wang, 2016).

1- Introduction

2- Experimental

3- Results and discussion

4- Conclusions

References

Abstract

To develop effective strategies for removing phenolic compounds, in-situ graphene oxide/manganese oxide (GO/MnOX, X = 2, 3/4) composites were fabricated via a sustainable method by synchronously utilizing manganese ions and acidic liquid waste during synthesis of GO. Comparatively, traditionally ex-situ GO/MnO2 composites were synthesized to verify the difference between in-situ and ex-situ synthesis. Based on the schematic and mass flow analysis, in-situ synthesis exhibited better atom economy and less waste emission than ex-situ synthesis. Then, the results of batch experiments exhibited that GO/MnOX composites possessed higher removal efficiency and wider pH range for p-cresol (p-CR) and p-tert-butylphenol (p-TBP) than GO/MnO2 composites. The maximum removal capacities of GO/MnOX composites were 107.68 mg/g for p-CR and 135.41 mg/g for p-TBP. And GO/MnOX composites could retain high removal efficiency for p-TBP (>90%) after five recycles. For in-situ GO/MnOX composites, GO sheets not only promoted the adsorption of phenolic compounds and by-products, but also enhanced the oxidation capacity of MnOX via an electron transfer interaction. Especially, the detection of ring cleavage products indicated further oxidation for p-TBP. Possessing an eco-friendly fabrication strategy and augmented adsorption-oxidation capability, in-situ GO/MnOX composites are expected to be applied in the removal of phenolic compounds.

Introduction

Phenolic compounds have given rise to emerging concerns regarding human health and ecosystems due to their widespread use in the pharmaceutical, petroleum and petrochemical, pesticide, plastic, and paper industries (Danquah et al., 2018). Consisting of a hydroxyl group bonded directly to a benzene ring, phenolic compounds possess a stable conjugated system, leading to biological accumulation and poor biodegradability (Ou et al., 2018). Thus, an urgent need exists to develop an efficient method for removing phenolic compounds (Villar da Gama et al., 2018; Zhong et al., 2018). Various methods, including chemical oxidation (Jiang et al., 2015), adsorption (Villar da Gama et al., 2018), and membrane separation (Zagklis and Paraskeva, 2015), have been reported to remove phenolic compounds. Among them, oxidation constitutes an effective and attractive method due to the potential to disrupt the structural stability of pollutants (Wang et al., 2015). Manganese oxides, ubiquitous in natural soil and synthetic materials, are traditional and cost-effective adsorbents and oxidants in wastewater treatment. Especially, manganese oxides are able to oxidize various aromatic Lewis bases, such as phenolic and aniline compounds (Grebel et al., 2016; Wang et al., 2018b). Previous studies demonstrated that phenolic compounds are susceptible to oxidation by manganese dioxide (MnO2) through sequential one electrontransfer reactions, forming a series of intermediate products (Abdullah et al., 2017; Remucal and Ginder-Vogel, 2014). However, the intermediate products, such as phenolic multimer and benzoquinones, would be released back into the aqueous solution.

Aluminum manufacturing has been reported as one of the largest industries and wastewater produced from the aluminum industry may cause significant environmental problems due to variable pH, high heavy metal concentration, conductivity, and organic load. The management of this wastewater with a high pollution load is of great importance for practitioners in the aluminum sector. There are hardly any studies available on membrane treatment of wastewater originated from anodic oxidation. The aim of this study is to evaluate the best treatment and reuse alternative for aluminum industry wastewater using membrane filtration. Additionally, the performance of chemical precipitation, which is the existing treatment used in the aluminum facility, was also compared with membrane filtration. Wastewater originated from anodic oxidation coating process of an aluminum profile manufacturing facility in Kayseri (Turkey) was used in the experiments. The characterization of raw wastewater was in very low pH (e.g., 3) with high aluminum concentration and conductivity values. Membrane experiments were carried out with ultrafiltration (PTUF), nanofiltration (NF270), and reverse osmosis (SW30) membranes with MWCO 5000, 200–400, and 100 Da, respectively. For the chemical precipitation experiments, FeCl3 and FeSO4 chemicals presented lower removal performances for aluminum and chromium, which were below 35% at ambient wastewater pH ~ 3. The membrane filtration experimental results show that, both NF and RO membranes tested could effectively remove aluminum, total chromium and nickel (>90%) from the aluminum production wastewater. The RO (SW30) membrane showed a slightly higher performance at 20 bar operating pressure in terms of conductivity removal values (90%) than the NF 270 membrane (87%). Although similar removal performances were observed for heavy metals and conductivity by NF270 and SW30, significantly higher fluxes were obtained in NF270 membrane filtration at any pressure that there were more than three times the flux values in SW30 membrane filtration. Due to the lower heavy metal (<65%) and conductivity (<30%) removal performances of UF membrane, it could be evaluated as pretreatment followed by NF filtration to protect and extend NF membrane life. The water treated by both NF and RO could be recycled back into the process to be reused with economic and environmental benefits.

Introduction

The aluminum industry contributes to the global economy and to the individual national economies of more than 30 countries. Primary aluminum production, the second most used metal in the world, has been recorded as 51 million tonnes (Das and Yin 2007; IAI 2013). Aluminum is used for varied applications in the construction industry, in transport, in electrical engineering, in packing, and in all kinds of equipment. Among them, production of fencing construction such as windows, doors, and wall and roof profile systems are common usages (Sergey 2011). Finished aluminum is produced by extrusion of the ingots and then the extruded pieces are anodized or covered (Dufour et al. 2001). The aluminum surface is converted to aluminum oxide in the anodizing process. Anodic coatings are impregnated with organic and inorganic dyes and pigments (Lyle et al. 2000) and sulfuric acid solutions are widely employed as electrolytes in anodizing (Sakon et al. 2005; Sanders 2012). The conventional anodizing process has environmental problems that producing huge amounts of wastewater with toxic reagents, heavy metals, and wide variation in pH (Sakon et al. 2005). Wastewater is one of the main issues for the aluminum industry because of significant environmental concerns and public health problems, since they usually contain a notable amount of heavy metals and even toxic elements with relatively high solubility (Agrawal and Sahu 2009). Heavy metals released into the environment bioaccumulate in living organisms and have a serious impact even in trace quantities (Lin et al. 2005; Murthy and Chaudhari 2008).

1- Introduction

2- Materials and methods

3- Results and discussion

4- Conclusion

References

Abstract

The aim of this research was to investigate the methyl orange degradation using hydrodynamic cavitation. The synthetic solutions simulated a real textile effluent containing dye and metals (iron and nickel) as a consequence of the corrosion of nickel-plated metal components of the plant during the production of textile materials. In the first series of experiments, the hydrodynamic cavitation was studied in terms of operating inlet pressure and pH of solution. Subsequently, a full factorial plan was performed to determine the main effects and interactions among the investigated factors: inlet pressure (pin), temperature (T), initial dye concentration (cMO/0), and treatment time (t). The results showed that inlet pressure, temperature and concentration had a significant positive effect on dye degradation, as well as the interactions temperature/dye concentration and pressure/time. The optimum operating conditions among those investigated were: cMO/0 = 5 ppm, pH = 2, pin = 0.6 MPa and t = 1 h, independently of temperature (T). In the above conditions, the degradation yields were near to 75% and the final concentration was less than 1 ppm. On the contrary, at cMO/0 = 20 ppm, pH = 2, pin = 0.6 MPa, T = 40 °C and t = 1 h, the degradation efficiency was about 56% and the final concentration was less than 9 ppm. A comparison among the experiments carried out in the absence and in the presence of iron and nickel showed that metals acted as catalysts and the energy required for the process with metal ions was 5 times smaller than that those required by the experiments conducted without the metals in solution, at the same operating conditions.

Introduction

Textile industry produces wastewaters containing several types of dyes. In the dyeing process, around 15% of the colorants is lost and discharged as industrial residual solutions [1, 2]. The treatment of such liquid wastes is a matter of great concern, due to their colour and toxicity. It is estimated that the annual world production of synthetic dyes in 2009 exceeded 900,000 tonnes and it is expected to grow a million tonnes every year [3-5]. The azo dyes are the most commonly used dyestuff and represent around 50-70% of the total production [6-8]. This type of dyes is characterized by the presence of a double nitrogen bonds (-N-N-) and it is widely used in the textile, paper and cosmetic industries [2, 9]. The release into the environment of azo-contaminated wastewaters poses severe problems of toxicity because of their bio recalcitrance for conventional aerobic wastewater treatment and the toxic aromatic intermediates. Therefore, the developments of effective methods for the removal of such polluting dyes is of major importance. From a literature survey, a lot of papers deals with the traditional decolourization techniques, and the work by Banat and co-workers [10] offers a good review. Physical and chemical processes, often combined with biological treatments dominate the scenery, mainly flocculation, flotation, membrane filtration, ion-exchange, coagulation precipitation, ozonisation and activated carbon adsorption [11]. Some of them showed almost satisfactory performances for the removal of dyes from textile wastewaters, while the process for the removal of sulfonated azo dyes had some lacks in the effective colour reduction. Anyway, the efficiency of the treatments depended on the initial characteristics of the wastewaters; moreover, one of the main drawbacks is the production of chemical sludge that needs to be proper disposed and the high consumption of chemicals which negatively affects the treatment costs. Fung et al. [11] in their paper outlined how to choose the technique based on the characteristics of dyeing wastewater. For an example, ozone treatment could be used to improve the biodegradability only if major pollutants contain conjugated double bonds or aromatic groups [12]; coagulation could be used to remove colloids and suspended solids; other types of bio-treatments could be applied to degrade the wastewater according to the biodegradability of the suspensions [13]; ultrafiltration process are indicated to remove solids (1-20 nm) and dissolved organics and macromolecules with molecular weight between 300 and 300,000 g/mol.

Over the last decade, poly(vinyl chloride) (PVC) has been one of the largest commodity thermoplastics used for numerous commercial and domestic applications, such as children toys, infants supply, medical supplies, packaging materials, and others.1,2 PVC has hard and brittle characteristics as a result of dipole present on each CACl bond, where an interaction among PVC chain exists that restricts chain motility.3 In order to enhance PVC characteristics, a compatible plasticizer is to be added to adjust its mechanical and thermal properties.4,5 This is performed via spacing out the PVC molecules to reduce the interaction between segments of polymer chains which leads to lowering the adhesion among molecules.2,3,6,7,11 Furthermore, adding a plasticizer to PVC lowers both the elasticity modulus and the glass transition point which leads to an enhancement in PVC processing properties.3,8,11 However, most plasticizers are not chemically bonded with PVC polymer chains; this allows them to leach from products into surrounding media.3,9 Hence, studying the exposure to these compounds has become an essential part of maintaining public health, and preventing associated adverse effects.10 There are many plasticizers used in PVC processing, one of those plasticizers is phthalate esters. Phthalate esters are petroleum-based products which are the most commonly used plasticizers in PVC processing. They represent more than 80% of PVC plasticizer market share.3,11 Phthalate esters group has a lot of members that are used in industry such as diisodecylphthalate (DIDP), di-2 ethyl hexyl phthalate (DEHP), di-octyl phthalate (DOP), and di-isononyl phthalate (DINP). All the industry-used members have very similar chemical and physical properties.12 Most of phthalate plasticizers are wellknown to be toxic, and may cause disorders in human reproduction system and endogenous hormone; owing to their migration from polymer matrix.3,13 Thus, it is recommended to use bio-compatible and sustainable alternative instead of phthalate esters. This would be from renewable resources and more secure materials than commercial phthalate.3,11 This review article depicts the harmful health effects of using commercial phthalate esters plasticizers in PVC products. It also describes two approaches; the first is a conventional production approach that uses chemical catalyst to obtain ester or epoxy from substrates such as vegetable oils.

دمای بالای شیمی کلر به روز شده و مکانیزم مهار شامل HCl و Cl2 دوباره مورد بررسی قرار گرفته است. از روش ترموشیمی از جدول ترموشیمی فعال (ATcT) برای به دست آمدن نتایج داده های بهبود یافته برای گونه های حاوی کلر استفاده کرد. خواص شیمیایی هیدروکلراید / Cl2 در اندازه گیری های تجربی بر اساس سرعت موجود در کتابهای مرجع در این مقاله مورد بحث است. با اتصال جدید زیر مجموعه هیدروکلراید / Cl2 با Politecnico دی میلان (POLIMI) مکانیزم گاز سنتز یک مکانیزم جنبشی متشکل از 25 گونه و 102 واکنش به دست آمد. اعتبار در داده های تجربی انتخاب شده از شعله ها ، لوله های شوک و راکتور جریان پلاگین انجام شد. سیستم حاوی Cl2 حساسیت بالا به Cl2 Cl2 + M ⇌ Cl + Cl + M; نشان داد ؛ سرعت ثابت برای این واکنش عدم قطعیت قابل توجه دارد و نیاز به تعیین دقیق درجه حرارت بالا وجود دارد.

1. مقدمه
خواص شیمیایی این کلر در احتراق و تبدیل به گاز سوخت جامد ، تا حدودی به دلیل امکان تولید گازهای گلخانه ای آلاینده و تا حدودی با توجه به پتانسیل های خورنده از کلر یک نگرانی است. به طور خاص زیست توده سالانه و کسری زباله خاص ممکن است مقدار قابل توجه کلر داشته [1] باشد. کلر معمولا در طول تجزیه حرارتی به عنوان کلر هیدروکربن (به عنوان مثال، کلرومتان، CH3Cl)، کلرید هیدروژن (هیدروکلراید) و یا کلرید قلیایی (به طور عمده محلول KCl) منتشر می شود. در طول احتراق کلر تا حد زیادی HCL اکسیده و ساطع خواهد شد. کلرید هیدروژن معمولا محصول کلر مورد نظر در احتراق است ، به دلیل اینکه آن به راحتی می تواند از گاز با یک فرایند سایش خارج شود. با این حال، کلر به عنوان یک منبع برای چند ماده شناخته شده است همچنین تشکیل دیوکسین / فوران از طریق مکانیسم هایی که ممکن است واکنش های فاز گاز با درجه حرارت بالا داشته باشد و همچنین واکنش در دمای پایین کاتالیست خاکستر [2-4].

مقاله سال 2016

هدف از این مطالعه، توصیف تلفیق ازونی فوتوکاتالیستی به عنوان ترکیبی از دو تکنیک مختلف برای تولید رادیکال هیدروکسیل است. فتوکاتالیز و تلفیق ازونی، برای برجسته کردن مزایای آن برای تصفیه آب و فاضلاب، برای مقایسه با این دو تکنولوژی استفاده می شود. بررسی گسترده ای در مورد مکانیسم ها، جنبش شناسی ها و جنبه های اقتصادی تلفیق ازونی فتوکاتالیستی برای بررسی اثرات هم افزایی تولید شده با استفاده از این روش اکسیداسیون برای تخریب، کانی سازی و سم زدایی از آلودگی های مختلف آلی در محیط های آبی انجام شده است. تأثیر پارامترهای آزمایشی مانند غلظت آلاینده، دوز ازون، بار فتوکاتالیستی و خواص آن، pH و دمای محلول، طول موج و شدت تابش و تأثیر حضور برخی از مواد در کارایی تلفیق ازونی فتوکاتالیستی مورد بحث قرار گرفته است. در نهایت، سیستم های فوتوکاتالیستی ناشی از پلاسما به عنوان یک رویکرد جدید برای رسیدگی به روش های تصفیه ی تلفیق ازونی فتوکاتالیستی معرفی می شود.

مقاله سال 2017

هدف مقاله حاضر تشخیص اثرات موقعیتهای نمونه گیری و بارگذاری موجی شکل بر روی خستگی کم چرخه درجه بالا (HTLCF) و عمر خستگی-خزشی یک سوپر آلیاژ GH4169 پایه نیکل سختکاری رسوبی شده، است. هر دو مکانیسم شکست و تغییر شکل در اینجا در نظر گرفته است. مشخص شد که HTLCF و عمر خزشی-خستگی نمونه ها بوسیله زیرساختارهای ناهمگن در موقیتهای مختلف تحت تاثیر قرار گرفته است. در مقایسه با آزمایشهای HTLCF، حضور زمانهای ساکن در آزمایشهای خزشی-خستگی، تمایل به کاهش تعداد چرخه های شکست را دارد. آسیب بین دانه ای در هر دو مرحله شروع و انتشار ترک خوردگی مشاهده شد. برای بارهای ساکن تحت تنش، آسیب بین دانه ای بطور عمده با حفره های دستیار-رسوب همراه است. با این حال اکسیداسیون برای حضور آسیب بین دانه ای برای بارهای ساکن تحت فشار، در نظر گرفته میشود.