جستجوی مقالات مرتبط با کلیدواژه « surfactant » در نشریات گروه « عمران »

Using different additives in order to increase the durability and mechanical resistance of concrete is one of the new approaches in concrete technology. In recent years, graphene has attracted attention due to its unique properties. However, the phenomenon of graphene accumulation in cement mixtures and high production costs have challenged its application in the concrete industry. For this purpose, it is necessary to use a graphene dispersing agent in the cement structure. This research used surfactants to spread graphene sheets in cement structures. This method has resulted in producing a cheap solution compared to typical methods, which can be used as an additive. The results of this research showed that the surfactant solution can increase mechanical properties at early ages. Detailed microstructure examination by FESEM analysis showed that the compounds containing 0.56 g/l of surfactant have a denser structure than the control sample, and also the compressive strength of the cement paste increased by 28.66% compared to the control sample at the age of 7 days. TGA and XRD analyses show that graphene played an effective role in nucleation and produced CH and C-S-H products in the cement structure. This solution can be used as a new additive in many construction projects.

In the present era, environmental pollution is a global crisis, increasing population growth and urban development, industrial expansion and unlimited use of natural resources, are among the increasingly important factors of pollutants (Reilley, 1996). Vocciante (2021) found in the study of stability in electrokinetic modification processes that the electrokinetic method is suitable for cleaning inorganic pollutants from clay. Zhou (2021) found that using the electrokinetic method is effective in removing heavy metals zinc, cadmium, and manganese from the soil and leads to the removal of about 72% of the pollutant from the soil sample. Vaishnavi (2021) in the study of bio-electrokinetic modification of diesel-contaminated environment with biosurfactant found that this method is an effective method for cleaning and cleaning soils contaminated with diesel hydrocarbons. Hanaei et al. (2021) found that the direct shear test showed that the adhesion of the soil sample increased and the friction angle decreased after oil contamination, and the permeability test showed that the contamination of the soil sample decreased the permeability of sandy soil and this change It is a function of the amount of oil and the viscosity of oils.

Pollution of soils containing petroleum products is one of the most important environmental challenges. Therefore, it is necessary to take measures for the purification of petroleum products, including diesel, to clean these compounds from the soil, various solutions are used, including the use of electrokinetic process. The result of the electrokinetic process in the soil is the movement of water, ions and charged particles due to the difference in electrical potential. In this study, the purification of diesel-contaminated clay by electrokinetic method in the presence of ABTS and saponin surfactants is investigated and the effect of pH control on catolite and anolite on the electrokinetic modification process of clay is evaluated, The results show that in the absence of the surfactant, the electrokinetic method has a very low removal efficiency of 3% to 7%, but in the presence of the surfactant, the efficiency is significantly increased by 20% to 54%, with pH control in Velit. and anolyte and the amount of active substance increase the level of efficiency of diesel removal from soil. With the use of Saponin, the lowest amount of removal at a concentration of 0.05% equal to 20% has been obtained, while ABTS has been able to remove about 54% of diesel at the highest concentration of surfactant (0.15%), in the continuation of the research A uniaxial test has been conducted to determine the unconfined compressive strength of the soil sample, which shows that the cleaning process increases the compressive strength of the soil by 15%.

In recent years, the use of nanoparticles to improve the properties of concrete has created a new perspective in concrete technology. Carbon nanotube is one of the most promising nanomaterials available to improve the performance of concrete and cement due to their excellent mechanical properties and chemical stability. Due to the tendency of nanotubes to shrink and be hydrophobic, proper distribution and dispersion of carbon nanotubes in concrete will be very effective in achieving the desired mechanical properties of concrete. Therefore, in this study, carbon nanotubes became hydrophilic using surface modification and covalent bonding. For the durability and stability of carbon nanotubes in water, C-type surfactants (CTAB), sodium dodecyl sulfate (SDS), polyethylene glycol (PEG) and polycarboxylate (PCE) were used. The results of visible ultraviolet (UV-vis) spectroscopy and compressive strength tests performed on concrete showed that the combination of PEG and PCE surfactants caused the optimal dispersion of carbon nanotubes so that it is compatible with the cement matrix and leads improve the mechanical properties of concrete. Experimental results show that the compressive strength of concrete samples of 7, 14 and 28 days containing 0.015% (cement weight) of carbon nanotubes with PEG and PCE surfactant increased by 3.1, 7.4 and 14.14%, respectively, compared to the reference sample; While in concrete samples containing carbon nanotubes and CTAB surfactant, due to the incompatibility of CTAB with cement and the low stability of dispersion of carbon nanotubes with CTAB, the concrete compressive strength of 7, 14 and 28 days (compared to the reference sample) decreased by respectively 5.6%, 17% and 9%.

Recently, the excellent performance of graphene-based materials has attracted civil engineering researchers in its application in cementitious mixtures. However, the application of graphene is hindered by its high cost and the agglomeration phenomenon in cementitious mixtures. In this regard, it is necessary to choose a dispersing agent with the ability to effectively separate graphene layers as well as improve mechanical properties and impermeability of cementitious mixtures. In this study, the effect of surfactant as a graphene separating agent from graphite on the mechanical properties and microstructure of cement paste containing water-dispersed graphene was investigated. The microstructure of the produced graphene reveals that the process of manufacturing graphene by peeling the surfactant leads to fragmentation and rupture of graphite. After 7 days of curing, the compressive strength of cement paste containing a mixture of 5 g / l graphite and 0.56 g / l surfactant increased by 28.66% compared to the control mixture. The crystallography and thermogravimetric results showed that graphene accelerates the formation of CH and C-S-H due to its nucleating effect in the cement matrix. Furthermore, the incorporation of graphene and surfactant into cement paste reduced the voids by 18.6%. This study shows that graphene dispersed in water produced by 0.56 g / l surfactant has the potential to be used as a novel additive in cement-based mixtures.

Cementitious composites are mainly used in the construction industry due to their good characteristics such as low cost, acceptable compressive strength, and easy access. However, there are many weaknesses in these materials, including low tensile strength, brittle behavior, and unacceptable durability (service life), which need to be improved to achieve more sustainable constructions. Nowadays, the using of nanotechnology have been growing and nanomaterials have been widely used in compound with a multitude of conventional materials. The outstanding chemical and physical properties of nanomaterials enable them to play a key role in various applications, such as modifying the material structure, ameliorating the properties of the material, and manufacturing modern multifunctional products. Recent advances in nanotechnology have led to produce nano-sized particles that can improve the durability performance of construction materials. Nanoparticles such as nano-silica, nano-Fe2O3, nano-clay, carbon nanotube (CNT), nano-Al2O3, nano-TiO2, and graphene oxide have been used to enhance the properties of cementitious composites. The performance of halloysite nanotube on the characteristics of cementitious composites has been studied less than other nanomaterials. Although the positive effects of nanomaterials such as halloysite nanotube (HNT) on the properties of cementitious composites have been proven, the very important issue of the correct and proper dispersion of nanomaterials in the cementitious environment has not been studied acceptably. The high surface energy and interparticle forces, including van der Waals, hydrogen bonding, and electrostatic interactions, make the nanomaterials highly susceptible to agglomeration. The aggregates of nanomaterials not only decrease their benefit but also act as potential weak spots in cementitious composites that can cause stress concentration, therewith diminishing the mechanical properties of cementitious composites. In this regard, the current paper investigated the effective factors on the agglomeration of halloysite nanotube (HNT) in the cementitious alkaline environment. Finally, this paper presented an approach for solving the problem of HNT agglomeration. Results showed that Ca2+, K+, and Na+ ions as alkaline agents of cement environment are the main factors to provide a state for HNT agglomeration. Among them, Ca2+ has more effect in agglomeration of halloysite nanotube due to the bridging effect between halloysite particles. From the results, the dispersion of HNT made better with increasing the alkalinity of cement environment until pH=11, while after this pH, the agglomeration of HNT started and the intense of agglomeration raised with the increase of pH, where it reached a maximum value at pH=13.5. Common approaches to nanoparticle dispersion are through physical methods (e.g., ultrasonic, high shear mixing, ball milling, etc.) and chemical methods (e.g., chemical modification of nanoparticle surfaces, use of dispersants such as surfactants, etc.). For the cementitious systems, a combination of ultrasonic and surfactant is mostly suggested. In this research, the effect of various surfactants on overcoming the agglomeration of halloysite nanotube in the cementitious environment was studied. The results indicated that the Polycarboxylate-based surfactant has better performance on improving the dispersion of HNT compared to that of other surfactants. Furthermore, incorporation of 3 wt% HNT enhanced the compressive, flexural and sorptivity of plain mortar up to 26, 22, and approximately 28%, respectively. The outcomes of the current paper display the fact that it is necessary to have special attention on the subject of the proper dispersion of nanomaterials in the cementitious environment for achieving the maximum efficiency of nanomaterials.

Understanding the combined effect of soil organic matter (SOM), surfactants and chelatant on the partitioning of polycyclic aromatic compounds and in soil/water systems and on their desorption is important to predict the effectiveness of surfactant-chelatant-enhanced remediation systems. In this paper the effect of soil organic matter’s content and presence of surfactants and a chelatant on desorption of six different polycyclic aromatic hydrocarbons namely acenaphthene , fluorine , phenanthrene , anthracene , fluoranthene , and pyrene was investigated and the results of phenanthrene was reported. It also investigates the effect of coexistence of three differenet heavy metals namely: lead, zinc and nickel on polycyclic aromatic hydrocarbons and their effects on desorption of these compounds. The basic soil was made from a mixture of kaolinite, montmorillonite and sand. Then this basic soil was spiked by two diffrenet level of organic matter through batch experiments to achieve three different soils named S0, S1 and S2 which has 0.33, 1.29 and 2.11 percent organic carbon, respectively. After that, this three different soils was spiked by heavy metals with the same way mentioned before (bathch experiments). As a result, six differenet soils was created under the name of: S0, S0M, S1, S1M, S2, S2M. and finally these six soils were spiked by mentioned polycyclic aromatic hydrocarbons. And finally the whole desorption experiments was done on these mentioned soils. Two surfactants chosen in this paper was triton x 100 and tween 80 and the chelatant was ethylene diamine tetraacitic acid (EDTA). Results showed that, surfactants improved the deorption of both heavy metals and polycyclic aromatic hydrocarbons and it also could be understood that triton x 100 had higher effectiveness than tween 80 in deorption of both heavy metals and polycyclic aromatic hydrocarbons. Furthermore it was found that soil organic matter had preventative effect on desorption of both heavy metals and polycyclic aromatic hydrocarbons. Both soil organic matter and surfactants are amphiphilic substances and because of that it is possible that this result is due to the sorption of surfactants into soil organic matter and consequently caused a reduction in desorption effectiveness of polycyclic aromatic hydrocarbons. and further increase in soil organic matter content caused more reverse effect on surfactants productivity. It was also found that, presence of lead, zinc and nickel could have preventative effect on desorption of polycyclic aromatic hydrocarbons too, and this could be due to some specific interactions like cation л binding between heavy metals and phenanthrene while they coexist in the interface of soil and water. Another reason of heavy metals preventative effect on desorption of polycyclic aromatic hydrocarbons could be due to their indirect effect through which, heavy metals act as an cation bridge between clay particles and organic matter mollecules and by this mean prevent soil organic matter mollecules to be dissolved in water. On the other hand scientists have proved that polycyclic aromatic hydrocarbons have great affinity to partition in to soil organic matter. Therefor by retaining more organic matter in soil through cation bridge mechanism, desorption of phenanthrene was reduced.

This study considers mobilization and desorption effects of biosurfactant produced in biodegradation of hydrocarbon-contaminated soils. 88 erlens with 100cc volume containing slurry contaminated kaolinite soil with 10000ppm and 50000ppm crude oil concentrations used as reactors. Mixed culture microorganisms were isolated from contaminated soils collected from Tehran refinery with total petroleum hydrocarbon then cultured in mineral solution. Results indicated that production of biosurfactant by microorganism cause to desorption and mobilization of hydrophobic hydrocarbon compounds. Further more shaking and aeration have been negligible effect on desorption and mobilization. Results also have shown that 19% of total reduction of TPH (about 40%) in twenty days concerns biosurfactant effects for 50000ppm samples. This effect is about 7% for 10000ppm samples.