Removal Of Hydrophobic Organic Contaminants Research Articles

Removal of Hydrophobic Contaminants from the Soil by Adsorption onto Carbon Materials and Microbial Degradation

The pollution of soil is a worldwide concern as it has harmful consequences on the environment and human health. With the continuous expansion of industry and agriculture, the content of hydrophobic organic pollutants in the soil has been increasing, which has caused serious pollution to the soil. The removal of hydrophobic organic contaminants from soil, aiming to recover environmental safety, is an urgent matter to guarantee sufficient food and water for populations. Adsorption has proven to be an effective and economically practicable method for removing organic contaminants. This paper summarizes the use of low-cost adsorbents, such as biochar and activated carbon, for removing hydrophobic organic contaminants from soil. Biochar is usually appropriate for the adsorption of organic contaminants via the adsorption mechanisms of electrostatic interaction, precipitation, and ion exchange. Biochar also has numerous benefits, such as being obtained from several kinds of raw materials, having low costs, recyclability, and potential for environmental treatment. This paper illustrates biochar’s adsorption mechanism for organic contaminants and discusses the microbial degradation of hydrophobic organic contaminants.

Development of novel multifunctional adsorbent by effectively hosting both zwitterionic surfactant and hydrated ferric oxides in montmorillonite

Intercalating various functional species into the interlayer space is an effective strategy to multi-functionalize 2D materials (e.g., montmorillonite, Mnt), but general limitations have emerged therefrom: (1) various intercalated species compete for the limited interlayer space, and (2) the neighboring intercalated species probably inhibit each other's reactivity. Herein, we have synthesized a novel Mnt-based multifunctional adsorbent (HFO-AZ16Mnt) via intercalation of zwitterionic surfactant (Z16), acid activation by chloric acid, and introduction of hydrated ferric oxides (HFOs). The acid activation can lead to formation of porous nanosilica, which serves as the new active sites for supporting HFO nanoparticles. Employing tetrachloroferrate (FeCl4−) as an anionic precursor of HFOs can help preserve the sulfonyl group (SO3−) of Z16 from being electrostatically occupied during the HFO introduction. As a result, HFO-AZ16Mnt can separately and effectively host Z16 and HFOs. The unique structure endows HFO-AZ16Mnt with the efficiency on simultaneous removal of hydrophobic organic contaminants, oxyanions, and heavy metal cations (nitrobenzene, phosphate, and Cd(II), respectively in this study) from water. Particularly, HFO-AZ16Mnt exhibits impressive capacity towards Cd(II) in both the single- (26.1 mg/g) and the multi-contaminant system (30.6 mg/g). This work has demonstrated a new strategy to multi-functionalize Mnt, and provided a promising novel Mnt-based multifunctional adsorbent for simultaneous and effective removal of organic and inorganic contaminants from water.

Importance of Sporopollenin Structure and Accessibility in the Sorption of Phenanthrene by Biota Spores and Pollens.

Although spores/pollens are so abundant and ubiquitous in the environment, the role of these natural organic matter concerning fate and transport of organic pollutants in the environment is neglected. Lipid-free fractions and sporopollenins were isolated from seven spores/pollens collected from lower and higher biota species and were characterized by elemental analysis, CO2 adsorption techniques, and advanced solid-state 13C nuclear magnetic resonance spectroscopy. Then, the sorption isotherms of phenanthrene (Phen) on all the samples were investigated by a batch technique. The sporopollenins were a highly cross-linked polymer including alkyl carbon, poly(methylene) carbon, and aromatic carbon as well as oxygen functionalities; additionally, their sorption capacities (Koc) for Phen reached up to 1 170 000 mL/g, suggesting that some of the sporopollenins were good biopolymeric sorbents for the removal of hydrophobic organic contaminants in aquatic media. A highly significant and positive correlation between the sorption capacity of Phen and the aliphaticity of the sporopollenins suggested that their structure was critical to Phen sorption. Meanwhile, the (O + N)/C atomic ratios and polar groups were significantly and negatively correlated with the sorption capacity of Phen, indicating that accessibility also played a significant role in the sorption process. Moreover, variable correlations between the sorption capacities (Koc) and the micropore volumes of the spore/pollen fractions were observed. This study sheds light on the importance of the polarity, microporosity, and structure of sporopollenins in the sorption process of Phen.

Ozone-encapsulated colloidal gas aphrons for in situ and targeting remediation of phenanthrene-contaminated sediment-aquifer

The hydrophobic polycyclic aromatic hydrocarbons (PAHs) are apt to adhere tightly to the sediments in aquifer and thus pose great threats to the aquatic environment of groundwater and surface water as well as human health. The present study constructed functionalized microbubbles, named colloidal ozone aphrons (COAs), by dissolving ozone-contained air into the nonionic surfactant (Tween-20) solution at the pressure of 300 kPa for the in situ remediation of phenanthrene (PHE)-contaminated sediments. The COA system aimed at improving the PHE elimination in terms of (i) enhancing the migration and transportation ability of the bubble system in the contaminated aquifer matrix, (ii) accurately desorbing the target hydrophobic contaminants from sediments, and (iii) reinforcing the in situ oxidation degradation immediately after or simultaneously when the PAHs are desorbed into the aqueous phase. Experimental results demonstrated that the COAs exhibited similar characteristics as the classical colloidal gas aphrons (CGAs), including the high stability (half-life time > 200 s), typical morphology and average bubble size (114–162 μm); higher air hold-up of COAs was achieved (i. e. > 20%) compared with the air-microbubbles (1–2%) obtained under the same generation conditions. Although the encapsulated ozone could oxidize the surfactant-layers, the properties and behaviors of COAs were not greatly affected. The surfactant multi-layers endowed the COAs with strong hydrophobic attraction with PHE, great migration capacity and enlarged oxidation area in the sediment matrix. Approximately 96.9% of PHE was removed from the sediments and 84.9% of the overall PHE was oxidized at the high ozone concentration of 0.6 mg/L when the initial PHE concentration was 240.0 μg/kg. The COA-involved remediation technology provided the insight of combining the processes of washing and oxidizing through adopting the particularly conceived microbubbles. The in situ and selective removal of hydrophobic organic contaminants from sediments in aquifer was well achieved in this study.

Effects of Tween 80 on Degradation of Pyrene in Soils Growing <em>Sorghum sudanese</em>

Phytoremediation is becoming a cost-effective technology for the in-situ clean up of sites polluted with Hydrophobic Organic Contaminants (HOCs). The major factors limiting phytoremediation are the mass transfer, rate of plant uptake and microbial biodegradation of HOCs. To evaluate the potential of surfactants to enhance phytoremediation for HOC-contaminated sites, the efficacy of Sudan grass ( Sorghum sudanense ), at the absence or presence of polyoxyethylene sorbitan monooleate (Tween 80), on the degradation of pyrene in soils were investigated and mechanisms of Surfactant-Enhanced Phytoremediation (SEPR) were discussed. Results showed that the presence of Tween 80 enhanced dissipation of pyrene at initial contents ranging from 20.24 to 321.42 mg/kg. During the 70-d SEPR-experiments, about 801.84~539.99‰ of pyrene was removed from planted soils, only 242.28~122.79‰ degradation of pyrene occurred in unplanted ones. With the presence of Tween 80, the dissipation ratios of pyrene in planted ones were increased up to 863.94~609.63‰, which was 77.27~129.14‰ higher than those in corresponding soils without surfactant. Among all possible pathways, contribution of plant-microbial interactions on dissipation of pyrene was the most significant, either at the presence (456.73‰) or absence (515.58‰) of Tween 80, were the primary means of contaminant degradation. Results suggested SEPR may be a feasible way for reinforcing removal of HOCs in contaminated sites.

Effects of Polyoxyethylene Sorbitan Monooleate on Degradation of Pyrene in Soils Growing Sorghum Sudanese

Phytoremediation is becoming a cost-effective technology for the in-situ clean up of sites polluted with Hydrophobic Organic Contaminants (HOCs). The major factors limiting phytoremediation are the mass transfer, rate of plant uptake and microbial biodegradation of HOCs. To evaluate the potential of surfactants to enhance phytoremediation for HOC-contaminated sites, the efficacy of Sudan grass, at the absence or presence of polyoxyethylene sorbitan monooleate (Tween 80), on the degradation of pyrene in soils were investigated and mechanisms of Surfactant-Enhanced Phytoremediation (SEPR) were discussed. Results showed that the presence of Tween 80 enhanced dissipation of pyrene at initial contents ranging from 20.24 to 321.42 mg/kg. During the 70-d SEPR-experiments, about 801.84~539.99‰ of pyrene was removed from planted soils, only 242.28~122.79‰ degradation of pyrene occurred in unplanted ones. With the presence of Tween 80, the dissipation ratios of pyrene in planted ones were increased up to 863.94~609.63‰, which was 77.27~129.14‰ higher than those in corresponding soils without surfactant. Among all possible pathways, contribution of plant-microbial interactions on dissipation of pyrene was the most significant, either at the presence (456.73‰) or absence (515.58‰) of Tween 80, were the primary means of contaminant degradation. Results suggested SEPR may be a feasible way for reinforcing removal of HOCs in contaminated sites.

Preparation and Characterization of Green Porous Palm Shell Based Activated Carbon by Two Step Chemical Activation Using KOH

The large quantity of agricultural waste materials that poses disposal challenge to our environment could be converted into useful products such as activated carbon (AC). Palm oil shell based porous AC was prepared by two step process using KOH as the chemical activant. Palm oil shell was carbonized at 800°C for 2 hours and activated using CO2 at same temperature for 1 hour which yield 23.27% fixed carbon. The AC was characterized by Langmuir surface area, BET surface area and pore volume of 410.7 m2/g, 350 m2/g and 0.2 cm3/g respectively, the FTIR analysis identified the presence of alkanes, carbonyls and hydroxyls as the main functional groups in the AC. Scanning electron microscopy images illustrates the gradual formation of pores from the precursor to the produced AC due to elimination of volatiles and contaminants in the material. However, the AC produced showed basic properties suitable for the removal of hydrophobic organic contaminants in water and wastewater.

Cysteine-β-cyclodextrin enhanced phytoremediation of soil co-contaminated with phenanthrene and lead.

It is necessary to find an effective soil remediation technology for the simultaneous removal of hydrophobic organic contaminants and heavy metals from contaminated soils. In this work, a novel cysteine-β-cyclodextrin (CCD) was synthesized by the reaction of β-cyclodextrin with cysteine, and the structure of CCD was confirmed by (1)H-NMR, (13)C-NMR, FT-IR spectroscopy and elemental analysis. Pot-culture experiments were conducted to investigate the effects of CCD on the phytoremediation of soil co-contaminated with phenanthrene and lead. The results showed that CCD can enhance the phytoremediation of soil co-contaminated with phenanthrene and lead. When CCD was added to the co-contaminated soil, the concentrations of phenanthrene and Pb in roots and shoots of ryegrass (Lolium perenne L.) significantly increased, the presence of CCD is beneficial to the accumulation of phenanthrene and Pb in ryegrass, and the residual concentrations of phenanthrene and Pb in soils significantly decreased. Under the co-contamination of 500 mg Pb kg(-1) and 50 mg PHE kg(-1), the bioconcentration factor of phenanthrene and Pb in the presence of CCD was increased by 1.43-fold and 4.47-fold, respectively. After CCD was added to the contaminated soils, the residual concentration of phenanthrene and Pb in unplanted soil was decreased by 18 and 25%, respectively. However, for the planted soil, the residual concentration of phenanthrene and Pb was decreased by 48 and 56%, respectively. CCD may improve the bioavailability of phenanthrene and Pb in co-contaminated soil; CCD enhanced phytoremediation technology may be a good alternative for the removal of hydrophobic organic contaminants and heavy metals from contaminated soils.

Removal of Hydrophobic Organic Contaminants (HOCs) from Aqueous Solution by Biomimetic Fat Cell (BFC) - The Behavior of Lindane

Based on the bioaccumulation characteristics of fat cell, an innovative agent, biomimetic fat cell (BFC) has been prepared by interfacial polymerization to remove residual hydrophobic organic contaminants (HOCs) from aqueous solution. BFC exhibited efficient lindane removal from aqueous solution, and 95 % lindane was removed by 20 mg/L BFC at 4.6, 9.3, 19.2, 27.6 and 38.2 μg/L initial concentrations. Removal rate experiments indicated that external film diffusion and intra-particle diffusion accounted for removal rate controlling together. Removal equilibrium fit Freudlich model well with high correlation coefficients. The thermodynamic parameters demonstrated that the removal was favored at low temperature and exothermic in nature.

Cosolvent flushing for the remediation of PAHs from former manufactured gas plants

Cosolvent flushing is a technique that has been proposed for the removal of hydrophobic organic contaminants in the subsurface. Cosolvents have been shown to dramatically increase the solubility of such compounds compared to the aqueous solubility; however, limited data are available on the effectiveness of cosolvents for field-contaminated media. In this work, we examine cosolvent flushing for the removal of polycyclic aromatic hydrocarbons (PAHs) in soil from a former manufactured gas plant (FMGP). Batch studies confirmed that the relationship between the soil–cosolvent partitioning coefficient ( K i ) and the volume fraction of cosolvent ( f c ) followed a standard log-linear equation. Using methanol at an fc of 0.95, column studies were conducted at varying length scales, ranging from 11.9 to 110 cm. Removal of PAH compounds was determined as a function of pore volumes (PVs) of cosolvent flushed. Despite using a high f c , rate and chromatographic effects were observed in all the columns. PAH effluent concentrations were modeled using a common two-site sorption model. Model fits were improved by using MeOH breakthrough curves to determine fitted dispersion coefficients. Fitted mass-transfer rates were two to three orders of magnitude lower than predicted values based on published data using artificially contaminated sands.

Removal of Hydrophobic Organic Contaminants from Aqueous Solutions by Sorption onto Biodegradable Polyesters

Sorption by biodegradable polyesters of several aromatic chemicals as model compounds for hydrophobic organic contaminants (HOCs) was studied. The biodegradable polyesters used were poly(butylene succinate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(ε-caprolactone), poly(butylene succinate/ terephthalate), and poly(L-lactic acid). Petrochemical plastics, low-density polyethylene and polyethylene terephtalate, were used for comparison. The target HOCs were biphenyl, bisphenol-A, dibenzofuran, diethylstilbestrol, nonyl-phenol, and chlorophenols. The treatment of the HOC solutions with each of the biodegradable polyesters resulted in the nearly complete removal of the chemicals by sorption from the aqueous phase, except for the case of poly(L-lactic acid). Low-density polyethylene adsorbed biphenyl and dibenzofuran selectively, and polyethylene terephtalate did not adsorb any of the HOCs. The adsorptive interaction between the plastics and the HOCs might be related to both the glass transition temperature of the former and the nature of the latter as defined by the Fujita's inorganicity/organicity ratio. The toxic effect of 3,5-dichlorophenol on bacte-rial growth in liquid culture was removed by the addition of a biodegradable polyester. These results provide a basis for the applicability of the biodegradable plastics as the adsorbents for the removal of HOCs from aquatic environments.

Zeolite-Templated Microporous Carbon As a Superior Adsorbent for Removal of Monoaromatic Compounds from Aqueous Solution

A microporous carbon with very high specific surface area and narrow pore size distribution was synthesized using Y zeolite as a template. The structural, porosity, and surface characteristics of the material were investigated by elemental analysis, N2 adsorption, powder X-ray diffraction, and Raman spectroscopy. The batch adsorption technique was performed to assess adsorption of three monoaromatic compounds, phenol, 1,3-dichlorobenzene, and 1,3-dinitrobenzene, on the synthesized carbon. Nonporous graphite, single-walled carbon nanotubes, and two commercial microporous activated carbons were also included as comparative adsorbents. The synthesized microporous carbon showed extraordinarily high adsorption affinity (comparable or higher than activated carbons and carbon nanotubes) for the three adsorbates, and very fast adsorption/ desorption kinetics (equilibrium reached less than 3 h) and complete adsorption reversibility for phenol. These adsorption properties were attributed to the large hydrophobic surface area and the regular-shaped, open and interconnected three-dimensional pore structure of the synthesized microporous carbon. Additionally, with normalization of adsorbent surface area adsorption of a bulky solute, 1,2,4,5-tetrachlorobenzene, was prominently higher on the synthesized carbon than on the activated carbons, due to alleviated size exclusion effect. Findings of the present work highlight the potential of using zeolite-templated carbons as effective adsorbents for removal of hydrophobic organic contaminants in water treatment.

Surfactant enhanced electrokinetic remediation of DDT from soils

Electrokinetic remediation has been investigated extensively as one of the noble technologies in remediation of metal contaminated soils. However, its applications in remediation of organic contaminants have been limited due to low solubilities of organics in water. In addition, most organic contaminants are non-ionic and therefore, they are not mobile under electrical field. The use of surfactants may increase the remediation efficiency by increasing the solubility of organics. Significant fraction of organics associated with soil, can be transferred to micellar phase, which then can be transported toward either cathode or anode, depending on the ionic group of surfactants. In this study, the removal of hydrophobic organic contaminants from a soil using electrokinetic method was investigated in the presence of surfactants. A nonionic surfactant, Tween 80, and an anionic surfactant, SDBS, were used in the experiments. DDT was chosen as the model organic contaminant. Phase distribution studies and column experiments were conducted. It was found that both Tween 80 and SDBS had similar solubilization potentials for DDT. It was also shown that the aqueous DDT mass could reach from 0.01 to 13% of the total mass in the presence of 7500 mg/L of SDBS. No significant movement of DDT was observed when Tween 80 was used in the column experiments. This was attributed to low rates of electroosmotic flows and strong interaction of Tween 80 with the soil. The amount of surfactant was not enough to mobilize DDT significantly in the column studies. On the other hand, electrokinetic transport with SDBS yielded much better results. DDT transport toward the anode within the negatively charged micelles overcame the opposite electrosmotic flow. This was attributed to the lower degree of interaction between the soil and SDBS, and the electrokinetic transport of negatively charged micelles.

Surfactant-enhanced electrokinetic removal of phenanthrene from kaolinite

Removal of hydrophobic organic contaminants (HOCs) using surfactant-enhanced electrokinetic (EK) method was studied in a model system. Kaolinite and phenanthrene were selected as a model clay soil and a representative HOC, respectively. Three different types of surfactants: APG (alkyl polyglucoside), Brij30 (polyoxyethylene-4-lauryl ether), and SDS (sodium dodecyl sulfate), were used to enhance the solubility of HOC. Characteristics of surfactants, such as surface tension, HOC solubility, and biodegradability were measured. In the case of Brij30 solution, phenanthrene solubility was higher than that of others. After 4 days, APG and Brij30 were degraded by 65% and 26% of the initial amount, respectively. However, degradation of SDS was hardly detected. Electroosmotic flow (EOF) of Brij30 solution was lower than others when the 0.1 M NaCl was used as electrolyte. Addition of the acetate buffer solution increased the EOF of Brij30 solution and enhanced removal of phenanthrene. Among three different surfactants tested, APG showed the highest removal efficiency.

Enhanced Removal of Hydrophobic Organic Contaminants by Settling Sediments in Western Lake Superior

Sediment cores from Lake Superior were collected, dated, and analyzed for a suite of hydrophobic organic contaminants (HOCs) including polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), and n-alkanes. The cores spanned an area from near Duluth/Superior in the western arm to the open waters of western Lake Superior. While accumulation rates for all HOCs were lower than in other Great Lakes, all analytes accumulated at a much higher rate in the western arm of Lake Superior closest to the Duluth/Superior area. The data indicate that HOCs in the western arm are removed from the water column more efficiently by settling particles resulting in higher accumulation rates and inventories. Atmospheric HOC loads focused via a terrestrial pathway by the St. Louis River also contribute to higher HOC loads to the western arm. A terrestrial biomarker, retene, and n-alkanes characteristic of higher terrestrial plant material exhibit a steep gradient decreasing from the western arm into the open waters of the western basin. A simple model was developed based on hydrophobicity and total suspended matter that supports the general observed pattern of PAH surface accumulation among the three coring sites. In particular, the model predicts a greater abundance of lower molecular weight PAHs in near-shore areas with higher total suspended material concentrations than in open waters. This phenomenon could explain the greater abundance of lower molecular weight PAHs observed in near-shore areas in other systems including the Black Sea and Lake Michigan. Differences in model results and measured surface accumulation rates and inventories of PAHs as well as carbon preference indices suggest that sediments from the western arm of Lake Superior are subject to local sources including uncombusted petroleum.

Removal of phenanthrene from soil by additive-enhanced electrokinetics

Removal of hydrophobic organic contaminants (HOCs) using an additive-enhanced electrokinetic method was studied in a model system. Kaolinite and phenanthrene were selected as a model clay soil and a representative HOC, respectively. Three different chemically-synthesized surfactants along with two different biosurfactants were used to remove phenanthrene. Hydrogen peroxide was also used to degrade phenanthrene. Electrokinetic (EK) column experiments were performed using these additives. When no additive was used, a removal efficiency of phenanthrene was 4.23% after 2 weeks. When surfactants were added in the EK system, the removal efficiencies after 2 weeks were as follows: APG 11.1%, Brij 30 6.31%, SDS 9.97%, MEL 16.2% and BS-UC 17.4%. Among surfactants, biosurfactants had higher removal efficiencies than chemically-synthesized surfactants. When hydrogen peroxide was used, 54.7% of initial amount was removed at a current of 5 mA for 2 weeks. Even a higher removal efficiency was achieved (84.2%) at 10 mA within 1 week. These results suggest a detailed future study on the chemical treatment by hydrogen peroxide incorporated with EK method to remove phenanthrene from clay soil.

Cyclodextrin-Enhanced Electrokinetic Removal of Phenanthrene from a Model Clay Soil

Removal of hydrophobic organic contaminants (HOCs) from saturated low-permeability subsurface environments using a solubility-enhanced electrokinetic remediation process is demonstrated for a model...