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Sampling and Analysis of Biological Volatile Organic Compounds
Published in Harriet A. Burge, Bioaerosols, 2020
Either chemical or thermal techniques can be used to desorb the VOCs from the sorbent and introduce them to the GC. In chemical desorption, a small quantity of high purity methanol, carbon disulfide, diethyl ether, or other compound is injected directly into the sorbent. In thermal desorption, the sorbent is heated to release the VOCs. Both techniques have been used for polymer sorbents (e.g., Tenax®), but chemical desorption is typically used with charcoal and silica gel media. Most fungal VOC studies have employed Tenax® with thermal desorption, which is faster than chemical desorption and avoids many interferences. Further, it generally offers better sensitivity since the sample is not diluted (Westendorf, 1985). On the other hand, thermal desorption requires more expensive equipment to control temperatures and gas flows.
Field-Scale Remediation of Crude Oil–Contaminated Desert Soil Using Various Treatment Technologies
Published in Ram Chandra, R.C. Sobti, Microbes for Sustainable Development and Bioremediation, 2019
Subhasis Das, Veeranna A. Channashettar, Nanthakumar Kuppanan, Banwari Lal
Based on the success achieved in the trial experiment, TERI was awarded a contract for a large-scale bioremediation project where the total volume that need to be treated was more than 2,00,000 m3 of crude oil–contaminated soil. Mostly, the contaminated soil came from sludge pit, effluent pits, and contaminated soil piles from oil production. The baseline concentration of total PHC of the crude oil–contaminated soil ranges between 3% and 5% (30,000 and 50,000 mg/kg). TERI treated these entire contaminated soils through thermal desorption and bioremediation in 48 months. Out of 2,17,000 m3 of crude oil–contaminated soil, approximately 1,60,000 m3 of contaminated soil was treated by landfarming using KT-Oilzapper microbes. The end products of degradation are CO2 and H2O, which are not harmful to the environment. On the other hand, approximately 57,000 m3 of contaminated soil was treated by thermal desorption, which is not at all environmentally friendly approach for the treatment of contaminated soil. Basically, thermal desorption is a widely accepted technology that provides a permanent solution at an economically competitive cost within a very short period; however, this technology is an energy-intensive process and damaging the soil properties in some extent. Moreover, thermal-based technology increases the carbon footprint in the atmosphere drastically, which causes global warming.
Engineering and ecological survey of oil-contaminated soils in industrial areas and efficient way to reduce the negative impact
Published in Vladimir Litvinenko, Scientific and Practical Studies of Raw Material Issues, 2019
Thermal desorption cleaning applied to a wide range of volatile and semi-volatile hydrocarbons, including refined fuels, tars, creosote, rubber wastes, and TPH (Yeung 2010). Thermal desorption in situ can take weeks or years, while thermal desorption ex situ can take several minutes to complete treatment. Known research reports that 45% of benzo(a)pyrene was removed in two years in situ, and it has been suggested that high molecular weight PAHs cannot significantly desorb in less than one year of in situ treatment. Light hydrocarbons can be desorbed much faster. It is known that thermal desorption in situ was shown to remove >99% of coal tar in several days (Hansen et al. 1998). The results of laboratory studies on the cleaning of oil contamination soils using thermal desorption processes are known. Studies have been conducted on model soil of the following composition: sand-oil; loam (5% humus) - oil; soil (20% humus) - oil with different oil content. As a result of research, it was established that the degree of extraction of petroleum products from soils is 80-98%, and the residual content of petroleum products does not exceed 0.5-1% of the mass of soil at any initial content of petroleum products (Trushlyakov 1999).
Petroleum hydrocarbons reduction by selected tropical grass species in oil-based drill cuttings contaminated soil
Published in International Journal of Phytoremediation, 2023
Charles Godspower Ologidi, Franklin B. G. Tanee, Ikechukwu O. Agbagwa
Drill cuttings are broken bits of formation rock materials brought to the earth surface during oil and gas drilling operations. They are classified as oil-based and water-based drill cuttings based on the drilling fluid (mud)—water-based (WBM) and oil-based drilling fluids (OBM)—used for drilling. The use of OBMs provide enhanced rate of penetration, reduced nonproductive time, and lowered overall operational costs (Mkpaoro et al. 2015). However, adverse environmental consequences from toxic levels of petroleum hydrocarbons, heavy metals, and salts have been recorded from using OBMs. Thus, the use of OBMs is strictly regulated in oil producing countries. For example, the Nigerian oil and gas regulator, Department of Petroleum Resources (DPR), stipulates treatment before disposal away from onshore and swamp. The implication is that oil-based drill cuttings (OBDCs) should be treated before disposal (EGASPIN 2018). Petroleum hydrocarbons are the most environment problematic constituents of OBDCs given that they are often above permissible limits (Kogbara et al. 2018; Zhu et al. 2019). Their presence in soil is followed by nutrient, especially nitrogen and phosphorus, depletion. The current practice in handling OBDCs is to reinject cuttings into approved waste disposal wells, volatilize contaminants by thermal desorption, and microbially degrade organic contaminants (Mkpaoro et al. 2015). Cutting’s reinjection and thermal desorption are costly, complex, and environment unfriendly. Hence, the need to adopt an alternative approach such as microbial degradation, which can be increased by augmenting with plants given that the soil region under the influence of plant roots and associated microorganisms (i.e., rhizosphere) is a hotspot for microbial activities (Kogbara et al. 2016). Besides, plants also carry out ecological functions like improving soil condition and reducing carbon in the atmosphere. Therefore, in the event of mishandling of OBDCs that leads to soil contamination, phytoremediation presents a simple, cost effective, and environment friendly soil remediation technology.
Recent advance in enhanced adsorption of ionic dyes from aqueous solution: A review
Published in Critical Reviews in Environmental Science and Technology, 2023
The purpose of desorption is to regenerate the adsorbent, increase the utilization cycles, and finally realize the minimum cost of wastewater treatment. The cost includes both the wastewater treatment and the disposal of saturated adsorbents. Meanwhile, the behavior of desorption and regeneration is conductive to elucidate the adsorption mechanism indirectly. At present, there are two main desorption techniques: thermal desorption and solvent elution. Thermal desorption technology is aimed at those adsorbents with strong thermal stability, such as AC and metal particles. Thermal desorption process relies on heat (or steam) to separate contaminants from the surface of the adsorbent or to crack them (Huang et al., 2022). Solvent elution is one of the most common regeneration methods, including acid, lye and organic solvents, such as HCl, H2SO4, HNO3, NaOH, methanol, ethanol, acetic acid, and acetone (Bushra et al., 2021). The reason why the adsorbent can be regenerated by solvent elution is that the dye adsorption behavior dominated by electrostatic interaction is reversible. The elution process of methanol, ethanol and acetone is similar phase dissolution principle, which uses organic solvent to dissolve organic dyes. Generally, acids have better desorption properties for cationic dyes, and basic solvents have better desorption properties for anionic dyes (Shi et al., 2022). Under acidic conditions, the positive charge of adsorbents is conducive to the adsorption of anionic dyes, and lye can weaken electrostatic interactions, and vice versa. For example, Huang et al. investigated the desorption behavior of adsorbed MB on CD/CA by 0.5 M HCl, ethanol and 0.5 M HCl + ethanol mixture (0.5 HCl in ethanol) respectively. HCl has the best elution performance, and the adsorption capacity of CD/CA has almost no loss after five adsorption–desorption cycles. Whereas, the adsorbent capacity regenerated by ethanol or 0.5 M HCl + ethanol mixture decreased significantly (decreased by 20–30%/5 cycles desorption) (Huang et al., 2018). As solvent elution does not destroy the structure of adsorbent, the adsorption capacity of adsorbent can generally be completely regenerated when it is thoroughly eluted. Therefore, the adsorption capacities of most ionic dye adsorbents are generally above 90% after five or six cycles of “adsorption-desorption” regeneration. For instance, surfactant has amphipathicity (hydrophilia and hydrophobicity), which can be stable and efficient adsorbed on the surface of solid materials. The Ni–Co–S/SDS composite can exist stably even after washing with methanol. The adsorption loss of the composite was less than 5% after five repeated sorption-washing process, which proved the stability of the surfactant grafted by impregnation method (Chowdhury et al., 2019). The similar stability of surfactant impregnated adsorbents has also been observed in many studies (Tang et al., 2017; Wang et al., 2022).