Surfactant Washing Research Articles

Remediation of oil-polluted soil using anionic and non-ionic composite biosurfactants

ABSTRACT Petroleum hydrocarbons as pervasive pollutants pose a significant threat to soil ecology and human health. Surfactant washing as an established technique can effectively remediate soils contaminated by hydrocarbons. Biosurfactants, which combine the properties of surfactants and environmental compatibility, have attracted increasing interest. However, due to the high production cost of biosurfactants, their practical application is restricted. This study addressed these limitations by selecting two biosurfactants, β-cyclodextrin (C1) and sodium carboxymethyl cellulose (C2), and developed a promising cleaning agent formula through compounding and the addition of suitable additives. When the volume ratio of C1 to C2 was 8:2 and an 8 g/L mixture of sodium humate and sodium carbonate electrolyte was added, the surfactant system’s surface tension reached a minimum, yielding optimal oil removal. The formation and synergistic behaviour of mixed micelles of surfactants were explained using ideal solution theory and the Rubingh model. By optimising the oil washing process parameters – normal temperature of 25 °C, pH 11, washing time of 2 h, solid–liquid ratio of 1:5, and oscillation frequency of 200 r/min – the oil removal rate achieved 76%. This cleaning agent, characterised by low production cost, straightforward application, environmental compatibility, and rapid, significant cleaning effect, shows potential for field-scale purification of petroleum-contaminated soil.

Passive swab versus grab sampling for detection of SARS-CoV-2 markers in wastewater

Early detection of the COVID-19 virus, SARS-CoV-2, is key to mitigating the spread of new outbreaks. Data from individual testing is increasingly difficult to obtain as people conduct non-reported home tests, defer tests due to logistics or attitudes, or ignore testing altogether. Wastewater based epidemiology is an alternative method for surveilling a community while maintaining individual anonymity; however, a problem is that SARS-CoV-2 markers in wastewater vary throughout the day. Collecting grab samples at a single time may miss marker presence, while autosampling throughout a day is technically challenging and expensive. This study investigates a passive sampling method that would be expected to accumulate greater amounts of viral material from sewers over a period of time. Tampons were tested as passive swab sampling devices from which viral markers could be eluted with a Tween-20 surfactant wash. Six sewersheds in Detroit were sampled 16–22 times by paired swab (4 h immersion before retrieval) and grab methods over a five-month period and enumerated for N1 and N2 SARS-CoV-2 markers using ddPCR. Swabs detected SARS-CoV-2 markers significantly more frequently (P < 0.001) than grab samples, averaging two to three-fold more copies of SARS-CoV-2 markers than their paired grab samples (p < 0.0001) in the assayed volume (10 mL) of wastewater or swab eluate. No significant difference was observed in the recovery of a spiked-in control (Phi6), indicating that the improved sensitivity is not due to improvements in nucleic acid recovery or reduction of PCR inhibition. The outcomes of swab-based sampling varied significantly between sites, with swab samples providing the greatest improvements in counts for smaller sewersheds that otherwise tend to have greater variation in grab sample counts. Swab-sampling with tampons provides significant advantages in detection of SARS-CoV-2 wastewater markers and are expected to provide earlier detection of new outbreaks than grab samples, with consequent public health benefits.

New perspective on human health risk from polycyclic aromatic hydrocarbons (PAHs) on surfaces of structures and buildings for industrial legacy before and after remediation

Industrial legacies are gradually becoming an important asset for urban regeneration. Coking plants, as one of the important industrial legacies, emit large amounts of polycyclic aromatic hydrocarbons (PAHs) in production, and the health risks of PAHs in the atmosphere and soil around coking plants have been fully recognized, but not much attention has been paid to the health risks of PAHs adsorbed on the surfaces of buildings. Therefore, we evaluated the health risks of PAHs adsorbed on the surfaces of buildings before and after the remediation and relocation of a legacy coking plant in China. Remediation was done in three steps: (1) mechanical grinding, (2) high-pressure blasting, and (3) surfactant washing. The concentration of total PAHs and the distribution of PAHs before remediation were different for each structure. The average total PAHs concentration before remediation was found to be between 0.16 mg m−2 and 329.77 mg m−2. The risk posed by the PAHs concentrations before and after remediation in each structure was quantified. For workers, surrounding residents, and tourists, the calculated carcinogenic risk ranged from 1.08 × 10−6 to 6.84 × 10−4, 9.00 × 10−6 to 4.89 × 10−3, and 7.44 × 10−6 to 3.22 × 10−3, respectively. After remediation, total PAHs concentrations ranged from non-detect to 1.15 g m−2. Our research has shown that PAHs adsorbed on the surface of coking plant buildings can pose serious health risks to human and require remediation before reuse. Mechanical grinding, high-pressure blasting, and surfactant cleaning can effectively remove PAHs adsorbed on the surface of buildings. The above results would provide different perspectives for the site risk assessment and remediation before the industrial legacies were reused.

Screening of bio-derived surfactants for soil washing of PAHs: effects of substrate sources and trace metals distribution

In this study, we screened the performance of aqueous extracts of Talinum triangulare (AET) and soap solution prepared from Hura crepitans seed oil saponified by aqueous solution of ashed plantain peels (HCS) for removal of naphthalene and phenanthrene from soil. The distribution of trace metals in the soil before and after soil washing was also investigated. The results revealed maximum removal efficiencies after 25 min washing time of 96.25, 96.14, and 25.70% naphthalene, for Tween 80, AET and HCS, respectively. While for phenanthrene, the recorded maximum removal efficiencies after 25 min washing time were: 91.80, 26.00, and 94.0 for Tween 80, AET and HCS, respectively. Based on results from other experiments, AET generally showed slightly lower removal efficiencies compared to the commercial Tween 80 surfactant. Also, the results revealed that the three remediants affected the distribution of trace metals (Cd, Pb, and Zn) in the soil after surfactant washing. Based on the amount of trace metals extracted, the performance of the three remediants are as follows: AET &gt; Tween 80 &gt; HCS. The performance of AET has been attributed to the presence of multiple heteroatomic moieties for trace metals adsorption and moderation of the acidic conditions of the soil.

Single hair fiber assessment techniques to discriminate between mineral oil and coconut oil effect on hair physical properties.

To utilize a matrix of single-fiber hair testing methodologies to mechanistically understand the impact of common oiling treatments-coconut oil and mineral oil-on hair strands. Further, the effect of hair twisting-experienced in everyday grooming practices-on hair strength was investigated under different scenarios. Study involved multiple surfactant wash cycles of hair swatches with and without overnight hair oil treatments. Instrumental testing was done on strands from hair swatches-Tensile Extension, Torsional Stretching, and Tensile Extension of twisted hair fibers. Differentiation was observed in tensile and torsional testing parameters with 20 wash cycles, while no statistical significance was observed in single wash. However, when we combine the two stresses together by extending the twisted hair strands, a clear differentiation was seen even in single cycle for coconut oil in comparison with mineral oil and surfactant wash. The differentiation in tensile parameters for twisted fibers becomes much more prominent with multiple cycles. Penetration of coconut oil in hair strands makes the fiber core more flexible and thus helps negotiate the torsional stress at the time of extension. Product benefit discrimination in single-strand testing can be amplified by combining multiple stresses in one testing methodology. Observing the consumer habits and incorporating the torsion component in standard tensile testing of hair helps differentiate the two commonly used hair oiling treatments. Coconut oil was found to significantly increase the tensile strength of twisted fibers owing to its penetration inside hair core.

Impact of non-rubber components on the branching structure and the accelerated storage hardening in Hevea rubber

Natural rubber (NR) contains cis-1,4-polyisoprene as well as a small quantity of non-rubber components, affecting the physical properties of NR, especially the storage hardening via gel formation. The free and/or linked non-rubber components were removed from NR by various treatments. The origin of gel formation in NR mainly resulted from proteins, which could be removed by enzymatic deproteinisation, surfactant washing or saponification treatment, and partly from phospholipids linked to NR molecule via H-bonding, which were decomposed by saponification or polar solvent treatment. The effect of the non-rubber components in NR on storage hardening was investigated by an accelerated storage hardening test (ASHT). The crude NR (CNR) containing proteins and lipids clearly showed the increase of gel content, suggesting the formation of crosslink structure during storage, resulting in the high plasticity number and Mooney viscosity after the ASHT. The gel content in protein-free NR did not change significantly only in washed NR (WSNR), but increased in the enzymatic deproteinised NR (DPNR). This resulted from the presence of residual proteins, such as oligopeptides. Interestingly, the gel content also reduced in the acetone extracted CNR (AE-CNR) and there was no significant effect on the storage hardening after ASHT, like WSNR. These were supposed to be due to the interaction or the participation of proteins and free fatty acids in the branching formation. Although the saponification could be decomposed branching at both terminal ends of the NR molecule, the protein and lipid residues occluded in the saponified NR (SPNR) affected the storage hardening. However, the flocculant remaining in the SPNR coagulated with acid and flocculant (AF-SPNR) would obstruct both gel formation and storage hardening.

Experimental approaches to creating a tissue-specific matrix for a bioartificial liver

Shortage of donor organs for liver transplantation in the treatment of end-stage liver disease dictates the need to develop alternative methods that include technologies on tissue engineering and regenerative medicine. Objective: to study the ability of a tissue-specific matrix from decellularized human liver fragments (DHLF) to maintain adhesion and proliferation of human adipose tissue-derived mesenchymal stem cells (hAT-MSCs) and HepG2 under static conditions and in a flow-through bioreactor. Materials and methods. Treatment with surfactants (SAS) – sodium dodecyl sulfate, Triton X-100 – followed by exposure to DNase was used for decellularization of human liver fragments (no more than 8 mm3). Biochemical screening included the determination of DNA quantity in the test samples. Efficiency of surfactant washing was assessed by the cytotoxicity of the matrix in the NIH 3T3 fibroblast culture. Viability and metabolic activity of cells were assessed via vital staining with a complex of fluorescent dyes LIVE/DEAD ® and PrestoBlue™ (Invitrogen, USA). Morphological examination of the liver cell-engineered constructs was carried out through histological staining and scanning electron microscopy with lanthanide contrast. Results. It was shown that the liver decellularization method used allows to obtain a biocompatible matrix with a residual DNA quantity &lt;1%, which is capable of maintaining adhesion and proliferation of hAT-MSCs and HepG2. On day 7 of cultivation in the bioreactor, there was formation of a single conglomerate of the DHLF matrix with numerous groups of viable cells with a high nuclear-cytoplasmic ratio. The urea content in the culture medium is 1.5 ± 0.1 mmol/L, exceeding that of samples obtained under static conditions. This indicates the metabolic activity of HepG2 in the composition of the obtained culture systems. It was shown that constant flow of the culture medium in the perfusion bioreactor increased the proliferative activity of HepG2 and allowed to provide a more uniform colonization by matrix cells in comparison with static cultivation conditions. Conclusion. The conditions for uniform colonization of DHLFs in a flow-through bioreactor with cell cultures were established. The ability of the matrix to maintain adhesion and proliferation of hADSCs and HepG2 for 11 days indicates that it could be used in liver tissue engineering.

Surfactant Washing to Remove Heavy Metal Pollution in Soil: A Review

Heavy metal pollution has pervaded many parts of the world, especially developing countries such as China. The discharge of wastewater containing heavy metals will cause soil pollution for a long time and harm to human health. Soil washing is an environmentally feasible and cost-effective approach for the clean-up of sites contaminated with heavy metals. As a relatively environmental protection agent, surfactants are widely used in soil washing. This paper generalized the methods of remediation of soil from heavy metals, expounded the mechanisms of soil washing by surfactant and the types of surfactants and summarized the application of different surfactants in washing heavy metals from soil. Finally, the application prospects and development trends of surfactant washing heavy metals from soil have been prospected.

Получение микродисперсного тканеспецифического децеллюляризованного матрикса из суставного хряща свиньи

A method for obtaining a microdispersed tissue-specific matrix from decellularized porcine articular cartilage while maintaining morphological and functional properties of the extracellular matrix with no signs of cytotoxicity was developed. The cartilage particle size distribution in suspension after cryogenic grinding was determined using laser diffraction analysis. The range of sizes of the obtained cartilage microparticles suggests the possibility of their administration by injection (<220 μm). The combination of stages, including three freeze/thaw cycles (–196/37°C) followed by treatment with solutions of surface-active substances (surfactants), sodium dodecyl sulfate and Triton X-100, and DNase resulted in the complete removal of non-decellularized microparticles. The residual DNA content was 9.11 ± 1.13 ng/mg of tissue. The effectiveness of surfactant washing was assessed by the cytotoxicity of the matrix on the culture of human adipose derived mesenchymal stromal cells (hADSCs). To assess the hemocompatibility of the obtained samples, their hemolytic activity was studied in vitro. The adhesion and proliferation of hADSCs on the matrix surface were studied on day 21 of cultivation. The matrix did not exhibit hemolytic activity and cytotoxicity with respect to hADSCs. hADSCs in the samples were actively proliferating on the matrix surface. The biocompatibility and hemocompatibility of the obtained matrix in vitro indicate its potential for application in cartilage regenerative medicine.

Combined Treatment of High Hydrostatic Pressure and Cationic Surfactant Washing to Inactivate Listeria monocytogenes on Fresh-Cut Broccoli.

This study was conducted to examine the inactivation effect of the combined treatment of high hydrostatic pressure (HHP; 400 MPa for 1, 3, and 5 min) and cationic surfactant washing (0.05% benzethonium chloride, BEC) against Listeria monocytogenes inoculated on fresh-cut broccoli (FCB). Washing with BEC at concentrations exceeding 0.05% resulted in 2.3 logreduction of L. monocytogenes counts on FCB, whereas HHP treatment had approximately 5.5- 5.6 log-reductions regardless of the treatment time. Scanning electron microscopy corroborated microbial enumeration, revealing that the combined treatment was more effective in removing L. monocytogenes from FCB than individual treatment with HHP or BEC. Color and total glucosinolate content were maintained after the combined treatment, although the hardness of the FCB slightly decreased. The results clearly suggest that the combined treatment of HHP and BEC washing has potential value as a new sanitization method to improve the microbial safety of FCB.

Comparison of residual NAPL source removal techniques in 3D metric scale experiments

This study compared four treatment techniques for the removal of a toluene/n-decane as NAPL (Non Aqueous Phase Liquid) phase mixture in identical 1 cubic meter tanks filled with different kind of sand. These four treatment techniques were: oxidation with persulfate, surfactant washing with Tween80®, sparging with air followed by ozone, and thermal treatment at 80°C. The sources were made with three lenses of 26×26×6.5cm, one having a hydraulic conductivity similar to the whole tank and the two others a value 10 times smaller. The four techniques were studied after conditioning the tanks with tap water during approximately 80days.The persulfate treatment tests showed average removal of the contaminants but significant flux decrease if density effects are considered. Surfactant flushing did not show a highly significant increase of the flux of toluene but allowed an increased removal rate that could lead to an almost complete removal with longer treatment time. Sparging removed a significant amount but suggests that air was passing through localized gas channels and that the removal was stagnating after removing half of the contamination. Thermal treatment reached 100% removal after the target temperature of 80°C was kept during more than 10d.The experiments emphasized the generation of a high-spatial heterogeneity in NAPL content. For all the treatments the overall removal was similar for both n-decane and toluene, suggesting that toluene was removed rapidly and n-decane more slowly in some zones, while no removal existed in other zones.The oxidation and surfactant results were also analyzed for the relation between contaminant fluxes at the outlet and mass removal. For the first time, this approach clearly allowed the differentiation of the treatments. As a conclusion, experiments showed that the most important differences between the tested treatment techniques were not the global mass removal rates but the time required to reach 99% decrease in the contaminant fluxes, which were different for each technique.

Treatment of Low-level BTEX-contaminated Soils by Anionic Surfactant Washing

Soil contamination generated by petroleum hydrocarbons, including benzene, toluene, ethylbenzene and xylene isomers (BTEX), has raised concern around the world. Soil flushing is the process of treating polluted soils with water, surfactants, or solvents, and it is usually feasible for the remediation of petroleumhydrocarbon contaminated soils. Surfactant-enhanced flushing was developed from the conventional pump-and-treat method. A mixture of water and surfactants is often applied to polluted soils and groundwater to improve the solubility of the pollutants during soil flushing. The objective of this study was to investigate the effects of applying anionic surfactants flushing on the treatment of low and high level BTEXcontaminated soils. A surfactant, sodium dodecylsulfate (SDS, anionic type), was used as a washing agent in the column experiments. Column studies were conducted to evaluate the efficiency of BTEX removal from unsaturated porous media using different concentrations of SDS for soil flushing. The soil column [4.2 cm (ID) × 12 cm (L)] was packed with low-level BTEX-contaminated soils (100 and 1,000 mg/kg) and DI water was pumped into the column with a flow rate of 11±1 mL/min. Results from the column study show that BTEX removal efficiencies varied from 63 to 95% when 0.5-2% (v/v) of SDS was pumped through the system. Higher BTEX removal efficiency was obtained when the higher surfactant concentration was applied. The results from this study provide insights into the surfactant washing technology, and will be useful in designing a scaled-up system for field applications.

Hybrid nanomaterials of WS2 or MoS2 nanosheets with liposomes: biointerfaces and multiplexed drug delivery.

Lipid containing hybrid materials are of significant interest for biointerface research and drug delivery applications, and a large number of previous studies have focused on graphene oxide (GO). In this work, novel hybrid materials made of transition metal dichalcogenides (TMDCs) and phosphocholine (DOPC) liposomes were prepared and compared with GO. All these inorganic materials are 2D nanosheets. DOPC liposomes are adsorbed by tungsten disulfide (WS2) as intact liposomes as indicated by cryo-TEM and liposome leakage assays. WS2 likely uses van der Waals forces for liposome adsorption as determined from urea, salt, and surfactant washing experiments. In addition, WS2 adsorbed doxorubicin (DOX) and DOPC liposomes synergistically. The adsorption capacity of DOPC on bare WS2 was 22.5% of the weight of WS2. After adsorbing DOX on WS2, the liposome adsorption capacity increased to ∼110%. Hydrogen bonding also contributed to liposome adsorption on DOX-loaded WS2. Confocal fluorescence microscopy confirmed the uptake of the DOPC/WS2 hybrid material by HeLa cells, and the co-delivery of DOX and calcein was achieved by loading calcein inside the liposomes. This study provides fundamental insights into the interaction between PC liposomes and WS2. Furthermore, preliminary biomedical applications of this hybrid material were explored.

Cosolubilization synergism occurrence in codesorption of PAH mixtures during surfactant-enhanced remediation of contaminated soil.

Surfactant-enhanced remediation (SER) has been widely applied in decontaminating PAH-polluted soil. Most researches focus on evaluating washing efficiency without considering pollutants' mutual interaction. This study aims to investigate cosolubilization effect between phenanthrene (Phe) and pyrene (Pyr) in nonionic surfactant Triton X-100 (TX100) solution on their codesorption performance from soil. Cosolubilization experiment showed that, when cosolubilized, solubility of Phe and Pyr in TX100 increased by 15.38% and 18.19%, respectively, as quantified by the deviation ratio of molar solubilization ratio in single and binary solute solubilization systems. The synergism may be due to the enlarged micelle volume caused by PAHs solubilized in the shell region of the micelle. The cosolubilization effect was further observed in the soil washing process. The strengthened TX100 solubilization capacity towards Phe and Pyr could increase the two PAHs' codesorption efficiency from soil, accompanied by synergistic extent of 6-15%. However, synergism in codesorption was weaker than that observed in the cosolubilization system, which may be related to surfactant loss to soil and PAH partition into soil organic matter and the sorbed surfactants. The improved remediation performance during codesorption of mixed PAHs implies the significance of combining PAHs' mutual interaction into evaluating SER, which may reduce the surfactant washing concentration and save remediation cost.

유사-펜톤 반응과 계면활성제에 의한 해양퇴적물의 PCBs 정화

Removal efficiency of PCBs in contaminated marine sediments treated by Fenton-like oxidation combined with surfactant was investigated in this research in order to achieve remediation of PCBs. A washing treatment using various concentrations of hydrogen peroxide (1% and 15%) and surfactants (Triton X-100, Tween 60 and Tween 80) was evaluated at various conditions in laboratory scale experiments. The mean removal efficiencies of tPCBs varied from 24.1 to 46.7% in the sediments for 1 hour duration of the treatments. The concentration of tPCBs in contaminated marine sediments after the simultaneous treatment with hydrogen peroxide and surfactant satisfied the domestic environmental standards for the beneficial use of sediments. When suitable surfactant was used for Fenton-like oxidation, the removal efficiency of tPCBs at low concentration of hydrogen peroxide was similar to that at high hydrogen peroxide concentration. Thus the efficient removal of PCBs in contaminated marine sediments could be achieved through treatment with Fenton-like oxidation combined with surfactant washing.

Clay mineral dependent desorption of pyrene from soils by single and mixed anionic–nonionic surfactants

Surfactant enhanced remediation (SER) has emerged as a promising option for the removal of PAHs-contaminated soil. The aim of this study was to enhance desorption of pyrene from soils containing various clay mineral compositions (e.g. montmorillonite and kaolin) by using single and mixed TX-100-SDBS surfactants. Results showed that the removal of pyrene from kaolin and kaolin-rich soil increased with time, while pyrene desorption from montmorillonite and montmorillonite-rich soil almost remained unchanged during the washing time from 5min to 48h, indicating that surfactant washing of pyrene-contaminated soil depended significantly on clay mineral composition of soil. Compared with the different ratios of mixed TX100-SDBS surfactants, single TX-100 had the highest efficiency in desorbing pyrene from kaolin-rich soils, while single SDBS was the most effective in desorbing pyrene from montmorillonite-rich soils. The observed effectiveness of surfactants to desorb was due to the different sorption of the surfactant onto the soils and clays. This study suggested the significance of considering clay mineral composition of soil for better application of SER of PAHs-contaminated environment.

Application of a three-stage remediation process to cleanup petroleum-hydrocarbon contaminated sediments

Sediments are usually the sinks for many waterborne pollutants, and thus, contaminated sediments need to be remediated to prevent the release of pollutants into the water bodies. The objective of this study was to develop a three-stage system to cleanup total petroleum hydrocarbons (TPH)-contaminated sediments. Sediments were collected from the Kaohsiung harbor with a TPH concentration of 8,105 mg/kg. Results from the sediment analyses show that sediments were mainly fine-grained silts, and the sediment organic matter content was about 19%. Thus, the surfactant washing method became an optimal option for the cleanup of TPH-contaminated sediments at this site. The three-stage scheme included the river water (RW) washing stage followed by the surfactant (Triton X-100) washing and Fenton-like oxidation stages. Batch experiments were conducted to evaluate the TPH removal efficiency by RW washing and surfactants washing with initial Triton X-100 concentrations of 0.5, 1, and 5% (w/w). In these oxidation experiments, three different hydrogen peroxide (H2O2) concentrations (0.6, 1.05, and 6 vol.%) were used to evaluate the TPH oxidation efficiency. Based on the results of the batch experiments, the three-stage operational process was performed using the optimal conditions from the batch experiments. The three-stage process was performed using 10 pore volumes (PVs) of RW washing followed by 30 PVs of Triton X-100 (0.5%) washing and 20 PVs of hydrogen peroxide (6%) oxidation. Results show that approximately 6% of TPH was removed after the RW washing stage. Up to 71% of TPH was removed by surfactant washing through mobilization and solubilization mechanisms. Approximately, 8% of TPH was removed through the Fenton-like oxidation, and a total of 86% of TPH was removed after the three-stage processes. This implies that the Fenton-like oxidation could be used as a polishment method for the TPH-contaminated sediment treatment. Results indicate that the proposed sediment treatment scheme could provide an efficient and cost-effective alternative for TPH-contaminated sediment remediation.

Effects of Different Purification Methods on Chicken Feather Keratin

Every year billion kilograms of unused feathers result from the poultry industry worldwide, which in effect impose a difficult disposal process to the environment. Chicken feathers are considered as a valuable and renewable keratin protein source, which could be used advantageously in a number of applications as alternatives to feather meal and feather disposal. Although the potential applications of keratin derived from chicken feathers have been investigated, the initial purification phase has not been fully described in the literature. Original chicken feathers contain many biological organisms along with other contaminants after plucking. Unprocessed chicken feathers are considered as potentially hazardous biological materials due to the presence of blood borne pathogens; therefore, the decontamination process is very important. The purpose of this work is to compare the effects of different purification techniques on chicken feathers prior to keratin isolation. These processes include surfactant washing, soxhlet extraction with ethanol, ozone, and sodium chlorite solutions. Thermogravimetric analysis, vibrational spectroscopy, and wide angle X-ray scattering were used to characterise the purified feathers prior to keratin extraction.

Investigation and Remedial Approach Development for a TCE Spill Site: A Case Study

A trichloroethene (TCE) plume has been discovered inside an industrial park located in Taiwan. The objectives of this study were to characterize the solvent spill site and prepare a corrective action plan (CAP) for site remediation. The following tasks have been performed under Taiwan Soil and Groundwater Remediation Act corrective action: (1) geophysical survey to verify the existence and fate of all potential contaminant sources in the vicinity of the avionics repair shop; (2) soil-gas survey and soil/groundwater analyses to delineate the lateral and vertical extent of contaminants in the subsurface; (3) application of field screening techniques to determine the presence of dense, non-aqueous-phase liquids (DNAPLs); (4) contaminant transport modeling; (5) evaluation of the remedial options, conduction of cost analysis, and selection of the optimal treatment system. Results from the site characterization indicate that an extended TCE plume existed in site groundwater, which needs to be contained and remediated. A two-phase remedial approach has been developed. Phase I was to contain the existing dissolved groundwater plume in the surficial aquifer and initiate mass removal of DNAPLs. Phase II was to conduct feasibility studies and possibly test surfactant washing and biobarrier techniques.

The Effect of Surfactant Extraction Method on Pore Characteristics of Mesoporous Carbonated Hydroxyapatite

Incorporated with pore sizes of 2-50 nm, CHA was found to be a promising drug delivery agent for disease treatment and could be a carrier for different types of proteins. A desired drug delivery system should consist of an ordered pore network, optimum pore size, and volume, as well as a high surface area, to allow a high drug adsorption rate, controllable drug loading, and release. However, until now, most results are still not up to expectation; since the BET surface area and pore volume obtained has been rather low, compared to the existing mesoporous silica. The objective of this work was to investigate the effect of surfactant washing on the pore characteristics and the importance of this step in the synthesis process of mesoporous carbonated hydroxyapatite (CHA). In this study, mesostructured CHA particles were prepared, via a self-assembly mechanism, between CHA and non-ionic surfactant (P123), using the co-precipitation synthesis method. The synthesized mesoporous CHA samples were washed five times using different types of solvents for surfactant removal. A sphere-like particle shape of CHA was observed under SEM for all samples; regardless of the type of solvent used. The formation of CHA was confirmed by FTIR analysis, where the carbonate ion peaks were observed in the spectrums. It was found that the mesoporous CHA with a high surface area was synthesized when high polarity solvents were used during surfactant washing. These results imply that high surface area mesoporous CHA can be obtained through surfactant washing, without applying calcination for surfactant removal, which may change the structure of the CHA during heat treatment.