The use of cork waste as a biosorbent for persistent organic pollutants-Study of adsorption/desorption of polycyclic aromatic hydrocarbons

Nanotechnology as an efficient and effective alternative for wastewater treatment: an overview

The increase in the surface and groundwater contamination due to global population growth, industrialization, proliferation of pathogens, emerging pollutants, heavy metals, and scarcity of drinking water represents a critical problem. Because of this problem, particular emphasis will be placed on wastewater recycling. Conventional wastewater treatment methods may be limited due to high investment costs or, in some cases, poor treatment efficiency. To address these issues, it is necessary to continuously evaluate novel technologies that complement and improve these traditional wastewater treatment processes. In this regard, technologies based on nanomaterials are also being studied. These technologies improve wastewater management and constitute one of the main focuses of nanotechnology. The following review describes wastewater's primary biological, organic, and inorganic contaminants. Subsequently, it focuses on the potential of different nanomaterials (metal oxides, carbon-based nanomaterials, cellulose-based nanomaterials), membrane, and nanobioremediation processes for wastewater treatment. The above is evident from the review of various publications. However, nanomaterials' cost, toxicity, and biodegradability need to be addressed before their commercial distribution and scale-up. The development of nanomaterials and nanoproducts must be sustainable and safe throughout the nanoproduct life cycle to meet the requirements of the circular economy.

Exploring the use of cork pellets in bar adsorptive microextraction for the determination of organochloride pesticides in water samples with gas chromatography/electron capture detection quantification

In this study, a biosorbent material with characteristics for the adsorption of organic compounds was used for a cork pellet-based bar adsorptive microextraction technique, as a new greener alternative for the determination of organochlorine compounds. Aldrin, chlordane, dieldrin, endrin, lindane, 4,4-DDD, 4,4-DDE, 4,4-DDT, α-endosulfan and β-endosulfan were analyzed in water samples (drinking water, stream water and river water) with separation/detection by gas chromatography and electron capture detection (GC/ECD). The parameters that can affect the sample preparation efficiency such as desorption solvent and time as well as extraction time and ionic strength were evaluated by multivariate and univariate designs. Cork pellets (10  ×  Ø 3 mm) were used for the extraction of 15 mL of sample in the optimal conditions: 60 min of agitation with no salt added to the sample, followed by desorption of the cork pellet with 120 µL of ethyl acetate for 30 min. The bar-to-bar RSD out with five different bars showed good results with RSD ≤ 15.6%, allowing the use of simultaneous extractions. LOD and LOQ values ranged from 3 to 15 ng L^-1 and 10 to 50 ng L^-1 respectively, and the determination coefficients were greater than 0.9869. The target analytes were not detected in the three analyzed samples. Therefore, the recovery study was performed fortifying the water samples. Analyte recovery ranged from 48.7 - 138.2% for drinking water, 40.2 - 128.2% for stream water and 67.5 - 128.7% for river water.

Advances in water treatment technologies for removal of polycyclic aromatic hydrocarbons: Existing concepts, emerging trends, and future prospects

In the last two decades, environmental experts have focused on the development of several biological, chemical, physical, and thermal methods/technologies for remediation of PAH-polluted water. Some of the findings have been applied to field-scale treatment, while others have remained as prototypes and semi-pilot studies. Existing treatment options include extraction, chemical oxidation, bioremediation, photocatalytic degradation, and adsorption (employing adsorbents such as biomass derivatives, geosorbents, zeolites, mesoporous silica, polymers, nanocomposites, and graphene-based materials). Electrokinetic remediation, advanced phytoremediation, green nanoremediation, enhanced remediation using biocatalysts, and integrated approaches are still at the developmental stage and hold great potential. Water is an essential component of the ecosystem and highly susceptible to PAH contamination due to crude oil exploration and spillage, and improper municipal and industrial waste management, yet comprehensive reviews on PAH remediation are only available for contaminated soils, despite the several treatment methods developed for the remediation of PAH-polluted water. This review seeks to provide a comprehensive overview of existing and emerging methods/technologies, in order to bridge information gaps toward ensuring a green and sustainable remedial approach for PAH-contaminated aqueous systems. PRACTITIONER POINTS: Comprehensive review of existing and emerging technologies for remediation of PAH-polluted water. Factors influencing efficiency of various methods, challenges and merits were discussed. Green nano-adsorbents, nano-oxidants and bio/phytoremediation are desirous for ecofriendly and economical PAH remediation. Adoption of an integrated approach for the efficient and sustainable remediation of PAH-contaminated water is recommended.

The High-Velocity Impact Behaviour of Kevlar Composite Laminates Filled with Cork Powder

The literature reports benefits when the cork powder obtained from industrial by-products is used as the filler of composite laminates. For example, while the fatigue life is insensitive to the presence of cork in the resin, significant improvements are achieved in terms of to low-velocity impact strength. However, in terms of ballistic domain, the literature does not yet report any study about the effect of incorporating powdered cork into resins. Therefore, this study intended to analyse the ballistic behaviour and damage tolerance of Kevlar/epoxy reinforced composites with matrix filled by cork powder. For this purpose, high-velocity impacts were studied on plates of Kevlar bi-directional woven laminates with surfaces of 100 × 100 mm2. It was possible to conclude that the minimum velocity of perforation is 1.6% higher when the cork powder is added to the resin, but considering the dispersion, this small difference can be neglected. In terms of damage areas, they are slightly lower when cork dust is added, especially for velocities below the minimum perforation velocity. Finally, the residual bending strength shows that these composites are less sensitive to impact velocity than the samples with neat resin. In addition to these benefits, cork powder reduces the amount of resin in the composite, making it more environmentally friendly.

Aromatic Potential and Bioactivity of Cork Stoppers and Cork By-Products

The characterization of natural waste sources is the first step on the reutilization process, circular economy, and global sustainability. In this work, the aromatic composition and bioactive compounds related to beneficial health effects from cork stoppers and cork by-products were assessed in order to add value to these wastes. Twenty-three aromatic compounds with industrial interest were quantified by gas chromatography coupled mass spectrometry GC–MS in both samples. Vanillins and volatile phenols were the most abundant aromatic families. Other aromatic compounds, such as aldehydes, lactones, terpenols, and alcohols, were also determined. Furthermore, the phenolic composition and the antioxidant activity were also evaluated. Overall, extracts showed high aromatic and antioxidant potential to be further used in different industrial fields. The recovery of these valuable compounds from cork stoppers and cork by-products helps to reuse them in agricultural, cosmetic, pharmaceutical, or food industries.

Returning to Nature for the Design of Sorptive Phases in Solid-Phase Microextraction

Green analytical chemistry principles aim to minimize the negative impact of analytical procedures in the environment, which can be considered both at close (to ensure the safety of the analysts) and global (to conserve our natural resources) levels. These principles suggest, among other guidelines, the reduction/minimization of the sample treatment and the use of renewable sources when possible. The first aspect is largely fulfilled by microextraction, which is considered to be among the greenest sample treatment techniques. The second consideration is attainable if natural products are used as raw materials for the preparation of new extraction phases. This strategy is in line with the change in our production system, which is being gradually moved from a linear model (take–make–dispose) to a circular one (including reusing and recycling as key terms). This article reviews the potential of natural products as sorbents in extraction and microextraction techniques from the synergic perspectives of two research groups working on the topic. The article covers the use of unmodified natural materials and the modified ones (although the latter has a less green character) to draw a general picture of the usefulness of the materials.

A comparison study of cleanup techniques for oil spill treatment using magnetic nanomaterials

Magnetic nanoparticles have been successfully used to recovery oil from oil spilled on water. Two different methods, floating and vortex, were employed to promote the interaction of four oil samples with different API (e.g., 10, 20, 28 and 45) spilled on seawater and deionized water with three magnetic materials, namely: magnetite nanoparticles (N); magnetic nanocomposites of yeast biomass provided by ethanol industry (Y); and magnetic nanocomposites of cork powder (C). The magnetic nanomaterials exposed to oil on water were taking out by a neodymium magnet, and the oil recoveries were determined by gravimetric analysis before and after lyophilization. The lyophilization was determinant to guarantee the accuracy of the experiments, and without this step, the masses of oil recovered would be overestimated due to the drag of water during the oil and magnetic material removal process. Three main factors, API, contact method and magnetic material, and two interactions (i.e., API × contact method, and contact method × magnetic material) presented a statistically significant effect on oil recovery. It was observed that oil recovery increases as API decreases, and it was possible to establish a model to predict the amount of recovered oil according to this effect. Higher oil recoveries were also obtained by magnetic nanocomposites of yeast biomass (Y), regardless of the contact method and type of water, recoveries of 23% and 100% for 45 and 10 API, respectively, employing around 20 mg of Y on 300 mg of spilled oil. These percentages correspond to 0.29 ± 0.01 kg/kg and 15.98 kg/kg of recovering oil by the magnetic procedure. The increase of mass of magnetic material improved the recovery of oils with higher APIs. The reusability of the spent materials presents potential for its application in oil spill cleaning technologies.

Preparation and characterization of magnetic nanomaterial and its application for removal of polycyclic aromatic hydrocarbons

Fe₃O₄@polyaniline, a Fe₃O₄-based magnetic core-shell material, was synthesized and its morphology and microstructure were characterized with transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and vibrating sample magnetometry. Polyaniline was modified onto the surface of Fe₃O₄ nanoparticles by a self-assembly method based on a two-step oxidative polymerization method. The new materials exhibited good adsorption to polycyclic aromatic hydrocarbons such as fluoranthene, pyrene and benzo[a]pyrene from environmental water samples due to the high affinities of polyaromatic hydrocarbons to polyaniline via π-π and van der Waals interactions. The experimental results indicate that the adsorption of polyaromatic hydrocarbons follows pseudo-second order kinetics and the adsorption isotherms conform to a Langmuir isotherm model. The thermodynamic parameters for polyaromatic hydrocarbons indicate that the adsorption process is spontaneous and endothermic in nature, but adsorption occurs via non-covalent interactions. This study indicated that the Fe₃O₄@polyaniline hybrid core-shell structure was proved to be a good adsorbent for polyaromatic hydrocarbons while exhibiting simple preparation, easy separation, low cost, high reusability and great potential applicability for removal of polyaromatic hydrocarbons from water.

Cork as a sustainable carbon source for nature-based solutions treating hydroponic wastewaters - Preliminary batch studies

Reusing by-products is an important strategy to ensure the preservation of natural capital and climate change mitigation. This study aimed at evaluating the potential of cork granulates, a by-product of winery industry, as an organic carbon (OC) source for the treatment of hydroponic wastewaters. First, chemical characterization was performed and discussed. Secondly, batch studies were performed using synthetic hydroponic wastewater to understand the role of particle size (PS), pH and contact time (CT) on the release of OC. The suberin is the major compound, representing >50%. It was noticed that a variance on the content of suberin across species, within the same species and depending on the extraction part (belly, cork and back) could be expected. >60% of the sample is composed by carbon while <1% was nitrogen (high C:N ratio), indicating a low risk of releasing organic nitrogen. The statistical results suggested that the main effect of PS on the release of OC is greater than both, CT and pH. The chemical release of OC gets slower with time, being this effect greater as the PS increase. Moreover, estimations showed that using the 4 mm PS, the amount of water treated would be twice the amount if the 8 mm PS had been used. The PS seems to play an important role at design nature-based solutions (NBS) focused on denitrification. The surface response methodology indicates a significant negative interaction between CT and PS suggesting that the mathematical model could be used for further optimization studies. The reuse of organic by-products as filter media seems to be an economic and environmentally friendly alternative to enhance denitrification in NBS, while preserving natural capital. However, further real scale and long-term experiments are needed to validate cork's potential as an "internal" OC source for NBS.

Treatment of a textile effluent by adsorption with cork granules and titanium dioxide nanomaterial

This study aimed to explore the efficiency of two adsorbents, cork granules with different granulometry and titanium dioxide nanomaterial, in the removal of chemical oxygen demand (COD), colour and toxicity from a textile effluent. The adsorption assays with cork were unsatisfactory in the removal of chemical parameters however they eliminated the acute toxicity of the raw effluent to Daphnia magna. The assay with TiO₂ NM did not prove to be efficient in the removal of colour and COD even after 240 min of contact; nevertheless it also reduced the raw effluent toxicity. The best approach for complete remediation of the textile effluent has not yet been found however promising findings were achieved, which may be an asset in future adsorption assays.

Effect of solid state fermentation of peanut shell on its dye adsorption performance

The effect of solid state fermentation of peanut shell to produce beneficial laccase and on its dye adsorption performance was evaluated. The resulting residues from solid fermentation were tested as sorbents (designated as SFs) in comparison to the raw peanut shell (RPS) for their ability to remove crystal violet from water. The fermentation process reduced the adsorption capacity (q_m) of SF by about 50%, and changed the sorptive behavior when compared to the RPS. The Langmuir model was more suitable for fitting adsorption by SFs. q_m was positively correlated with the surface area of peanut shell, but negatively correlated with acid detergent lignin content. For all the sorbents tested, the process was spontaneous and endothermic, and the adsorption followed both the pseudo 1st and 2nd order kinetic model and the film diffusion model. Dye adsorption efficiency was greater when SFs dispersed solution than when placed in filter packets.

Study of processes influencing bioavailability of pesticides in wood-soil systems: Effect of different factors

Lignocellulosic wastes and by-products containing lignin are now available in large amounts from forestry and industrial activities, and could be promising organic materials for the biosorption of pesticides by soils in order to reduce point-source pollution. Adding these materials to soil requires understanding the process of pesticide sorption-desorption by wood-soils, as sorption capacity could increase, with changes in pesticide bioavailability and final fate. The objective of this work was to study the effect that pine and oak wood added to soils had on the sorption/desorption of the pesticides linuron, alachlor, and metalaxyl. Experiments were conducted with two sandy loam and sandy clay soils each amended with two wood doses (5% and 50%) after different incubation times (0, 5 and 12 months). A low wood dose (5%) had no significant impact on the sorption (K_f) of alachlor, but K_f increased for linuron (up to 5.4-1.7 times) and metalaxyl (up to 4.4 and 8.6 times) in all wood-soil systems. The results were not significantly different after different incubation times. The desorption results indicated that wood decreases the sorption irreversibility of alachlor, and increases that of linuron and metalaxyl, with a varying effect of the wood-soil incubation time. The addition of a high wood dose to soil (50%) was more significant for increasing the sorption of all the pesticides, and the sorbed amounts remaining after desorption (>49% for linuron, >33% for alachlor and >6% for metalaxyl), although there was no apparent discrimination between the two types of woods. The role of the nature of the organic carbón (K_oc values) for sorption was evidenced for alachlor and metalaxyl, but not for linuron. These outcomes are of interest for extending wood application to soil as a barrier for avoiding environmental risk by point-source pollution due to the use and management of pesticides in farming systems.

Adsorption of methylene blue on an agro-waste oiltea shell with and without fungal treatment

A lignocellulosic waste oiltea shell (OTS) was evaluated as an inexpensive sorbent to remove methylene blue (MB) from aqueous solution. Fungal treatment of OTS increased the MB adsorption by modifying the physicochemical properties of OTS and simultaneously produced laccase as a beneficial co-product. Without fungal treatment, the maximum amount of adsorption (q_m) of MB by OTS was 64.4 mg/g, whereas the treatment with fungus Pycnoporus sp. and Trametes versicolor increased q_m up to 72.5 mg/g and 85.7 mg/g, respectively. This is because of the improved surface area and pore sizes as well as altered chemical compositions. The equilibrium sorption data for OTS both with and without treatment fitted to the Langmuir model, and the sorption rate data well fitted to the pseudo second-order kinetic model. The changes in free energy (ΔG°) and separation factor (R_L) indicated that the sorption was spontaneous and favorable. Scanning electron microscopy and Fourier transform infrared spectroscopy showed the changes in the surface morphology and functional groups of OTS after fungal treatment. The agro-waste OTS could be utilized as a low-cost adsorbent for efficient dye removal, and fungal treatment can serve as a mild and clean technique to increase the adsorptive capacity of OTS.

Fungal biodegradation of anthracene-polluted cork: A comparative study

The efficiency of cork waste in adsorbing aqueous polycyclic aromatic hydrocarbons (PAHs) has been previously reported. Biodegradation of contaminated cork using filamentous fungi could be a good alternative for detoxifying cork to facilitate its final processing. For this purpose, the degradation efficiency of anthracene by three ligninolytic white-rot fungi (Phanerochaete chrysosporium, Irpex lacteus and Pleurotus ostreatus) and three non-ligninolytic fungi which are found in the cork itself (Aspergillus niger, Penicillium simplicissimum and Mucor racemosus) are compared. Anthracene degradation by all fungi was examined in solid-phase cultures after 0, 16, 30 and 61 days. The degradation products of anthracene by P. simplicissimum and I. lacteus were also identified by GC-MS and a metabolic pathway was proposed for P. simplicissimum. Results show that all the fungi tested degraded anthracene. After 61 days of incubation, approximately 86%, 40%, and 38% of the initial concentration of anthracene (i.e., 100 µM) was degraded by P. simplicissimum, P. chrysosporium and I. lacteus, respectively. The rest of the fungi degraded anthracene to a lesser extent (<30%). As a final remark, the results obtained in this study indicate that P. simplicissimum, a non-ligninolytic fungi characteristic of cork itself, could be used as an efficient degrader of PAH-contaminated cork.

Binding interactions between suberin monomer components and pesticides

Understanding the role of biomacromolecules and their interactions with pollutants is a key for elucidating the sorption mechanisms and making an accurate assessment of the environmental fate of pollutants. The knowledge of the sorption properties of the different constituents of these biomacromolecules may furnish a significant contribution to this purpose. Suberin is a very abundant biopolymer in higher plants. In this study, suberin monomers isolated from cork were analyzed by thermally-assisted methylation with tetramethylammonium hydroxide (TMAH) in a pyrolysis unit coupled to gas chromatography-mass spectrometry (GC/MS). The isolated monomer mixture was used to study the sorption of three pesticides (isoproturon, methomyl and oxamyl). The modes of pesticide-sorbent interactions were analyzed by means of two modeling calculations, the first one representing only the mixture of suberin monomers used in the sorption study, and the second one including glycerol to the mixture of suberin monomers, as a building block of the suberin molecule. The results indicated that the highest sorption capacity exhibited by the sorbent was for isoproturon (33%) being methomyl and oxamyl sorbed by the main suberin components to a lesser extent (3% and<1%, respectively). In addition to van der Waals interactions with the apolar region of sorbent and isoproturon, modeling calculations evidenced the formation of a hydrogen bond between the isoproturon NH group and a carboxylic oxygen atom of a suberin monomer. In the case of methomyl and oxamyl only weak van der Waals interactions stabilize the pesticide-sorbent adducts. The presence of glycerol in the model provoked significant changes in the interactions with isoproturon and methomyl.

Typical low cost biosorbents for adsorptive removal of specific organic pollutants from water

Specific organic pollutants (SOPs) such as phenolic compounds, PAHs, organic pesticides, and organic herbicides cause health and environmental problems due to their excessive toxic properties and poor biodegradability. Low-cost biosorbents are considered as a promising alternative for conventional adsorbents to remove SOPs from water. These materials have several advantages such as high sorption capacities, good modifiability and recoverability, insensitivity to toxic substances, simple operation in the treatment processes. However, previous reports on various types of biosorbents for removing SOPs are still moderately fragmented. Hence, this paper provides a comprehensive review on using typical low-cost biosorbents obtained from lignocellulose and chitin/chitosan for SOPs adsorption. Especially, their characteristics, biosorption mechanism together with utilization for eliminating SOPs are presented and discussed. The paper also gives a critical view regarding future applications of low-cost biosorbents in SOPs-contaminated water treatment.

New insights into the interactions between cork chemical components and pesticides. The contribution of π-π interactions, hydrogen bonding and hydrophobic effect

The role of chemical components of cork in the sorption of several pesticides has been investigated. For this purpose raw cork and three cork extracted fractions (i.e. cork free of aliphatic extractives, cork free of all extractives and cork free of all extractives and suberin) were used as sorbent of three ionic pesticides (propazine, 2,4-dichlorophenoxy acetic acid (2,4-D) and alachlor) and five non-ionic pesticides (chlorpyrifos, isoproturon, metamitron, methomyl and oxamyl) with a logKow within the range -0.47 to 4.92. The effect of cations on the ionic pesticides, propazine and 2,4-D sorption was also analyzed. Results indicated that the highest yields were obtained for chlorpyrifos and alachlor sorption onto raw cork (>55%). After removal of aliphatic extractives sorption of all pesticides increased that ranged from 3% for propazine to 31% for alachlor. In contrast, removal of phenolic extractives caused a sorption decrease. Low sorption yields were obtained for hydrophobic pesticides such as metamitron, oxamyl and methomyl (<11%) by using all cork fractions and extremely low when using raw cork (<1%). FTIR analysis was useful to indicate that lignin moieties were the main components involved on the sorption process. Modelling calculations evidenced that π-stacking interactions with the aromatic groups of lignin play a major role in determining the adsorption properties of cork toward aromatic pesticides. Results presented in this paper gain insights into the cork affinities for pesticides and the interactions involved in the sorption process and also enables to envisage sorption affinity of cork for other organic pollutants.

The effect of structural compositions on the biosorption of phenanthrene and pyrene by tea leaf residue fractions as model biosorbents

To enhance the removal efficiency of polycyclic aromatic hydrocarbons (PAHs) by natural biosorbent, sorption of phenanthrene and pyrene onto raw and modified tea leaves as a model biomass were investigated. Tea leaves were treated using Soxhlet extraction, saponification, and acid hydrolysis to yield six fractions. The structures of tea leaf fractions were characterized by elemental analysis, Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM). The amorphous cellulose components regulated the sorption kinetics, capacity, and mechanism of biomass fractions. The adsorption kinetics fit well to pseudo-second-order model and isotherms followed the Freundlich equation. By the consumption of the amorphous cellulose under acid hydrolysis, both the aliphatic moieties and aromatic domains contributed to total sorption, thus sorption capacities of the de-sugared fractions were dramatically increased (5–20-fold for phenanthrene and 8–36-fold for pyrene). All de-sugared fractions exhibited non-linear sorption due to strong specific interaction between PAHs and exposed aromatic domains of biosorbent, while presenting a relative slow rate because of the condensed domain in de-sugared samples. The availability of strong sorption phases (aromatic domains) in the biomass fractions were controlled by polar polysaccharide components, which were supported by the FTIR, CHN, and SEM data.

Organic xenobiotics removal in constructed wetlands, with emphasis on the importance of the support matrix

Constructed wetlands (CWs) are increasingly popular as an efficient and economical alternative to conventional wastewater treatment processes for removal, among other pollutants, of organic xenobiotics. In CWs, pollutants are removed through the concerted action of their components, whose contribution can be maximized by careful selection of those components. Specifically for non-biodegradable organic pollutants, the materials used as support matrix of CWs can play a major role through sorption phenomena. In this review the role played by such materials in CWs is examined with special focus on the amount of research that has been conducted to date on their sorption properties relatively to organic compounds. Where available, the reports on the utilization of some of those materials on pilot or full-scale CWs are also recognized. Greatest interest has been directed to cheaper and widely available materials. Among these, clays are generally regarded as efficient sorbents, but materials originated from agricultural wastes have also gained recent popularity. Most available studies are lab-scale batch sorption experiments, whereas assays performed in full-scale CWs are still scarce. However, the available lab-scale data points to an interesting potential of many of these materials for experimentation as support matrix of CWs targeted for organic xenobiotics removal.

An integrated approach to understanding the sorption mechanism of phenanthrene by cork

Previous studies have shown the high sorption affinity of polycyclic aromatic hydrocarbons by cork. The aim of the present work is to go further by investigating the sorption mechanism of polycyclic aromatic hydrocarbons (exemplified by phenanthrene) on cork and the availability of the chemical components (i.e. lignin, suberin, holocellulose and extractives) to retain phenanthrene. Two approaches were integrated to reach this objective: (1) statistical multivariate analysis to obtain correlations between the sorption capacity, measured as K(oc), and the sorbent properties (i.e. polarity, acidic functional groups, %dichloromethane extractives, %ethanol and water extractives, %suberin, %lignin and %holocellulose) and (2) modeling calculations to obtain information on interaction at the molecular level. The statistical multivariate analysis demonstrated a strong and positive correlation between K(oc) and the lignin content as well as negative correlations between K(oc) and the phenolic groups and %dichloromethane extractives contents. The modeling study showed that the lignin-phenanthrene interaction is mostly hydrophobic in nature being largely determined by the π-stacking interaction between the aromatic groups of the interacting partners. This result justifies the observed correlations as dichloromethane extractives, being hydrophobic, compete with phenanthrene adsorption, whereas phenolic groups, as well as negatively charged groups, enhance the hydrophilic character of the sorbent surface, thus hindering the adsorption of phenanthrene.

Use of cork powder and granules for the adsorption of pollutants: a review

Cork powder and granules are the major subproducts of the cork industry, one of the leading economic activities in Portugal and other Mediterranean countries. Many applications have been envisaged for this product, from cork stoppers passing through the incorporation in agglomerates and briquettes to the use as an adsorbent in the treatment of gaseous emissions, waters and wastewaters. This paper aims at reviewing the state of the art on the properties of cork and cork powder and their application in adsorption technologies. Cork biomass has been used on its original form as biosorbent for heavy metals and oils, and is also a precursor of activated carbons for the removal of emerging organic pollutants in water and VOCs in the gas phase. Through this literature review, different potential lines of research not yet explored can be more easily identified.

The use of lightweight expanded clay aggregate (LECA) as sorbent for PAHs removal from water

Lightweight expanded clay aggregate (LECA) has been explored as a sorbent for the removal of PAHs (phenanthrene, fluoranthene and pyrene) from water. The efficacy of LECA as a sorbent for PAHs was assessed using contact time, mass of sorbent and sorption isotherms in a series of batch experiments. Maximum (optimum) sorption was reached at 21 h after which the amount of PAHs sorbed remained almost constant. Batch experiments were conducted by shaking a 100ml solution mixture of individual PAHs (containing 0.02 mg/L) with LECA. The maximum sorption was 70.70, 70.82 and 72.12%, respectively for phenanthrene, fluoranthene and pyrene when a mass of 0.2 g of sorbent was used. There was an increase in sorption as a result of an increase in mass of sorbent until a maximum was reached at a mass of 4.0 g LECA with 92.61, 93.91 and 94.15% sorption of phenanthrene, fluoranthene and pyrene respectively. Sorption data were fitted to the linearised forms of the Freundlich and Langmuir isotherm models to determine the water-LECA partitioning coefficient. Physical sorption caused by the aromatic nature of the compounds was the main mechanism that governed the removal process while the hydrophobicity of the PAHs also influenced the sorption capacity. LECA can be used as an alternative method for aqueous PAHs removal.

Analysis and comparison of inertinite-derived adsorbent with conventional adsorbents

To increase U.S. petroleum energy-independence, the University of Texas at Arlington (UT Arlington) has developed a coal liquefaction process that uses a hydrogenated solvent and a proprietary catalyst to convert lignite coal to crude oil. This paper reports on part of the environmental evaluation of the liquefaction process: the evaluation of the solid residual from liquefying the coal, called inertinite, as a potential adsorbent for air and water purification. Inertinite samples derived from Arkansas and Texas lignite coals were used as test samples. In the activated carbon creation process, inertinite samples were heated in a tube furnace (Lindberg, Type 55035, Arlington, UT) at temperatures ranging between 300 and 850 degrees C for time spans of 60, 90, and 120 min, using steam and carbon dioxide as oxidizing gases. Activated inertinite samples were then characterized by ultra-high-purity nitrogen adsorption isotherms at 77 K using a high-speed surface area and pore size analyzer (Quantachrome, Nova 2200e, Kingsville, TX). Surface area and total pore volume were determined using the Brunauer Emmet, and Teller method, for the inertinite samples, as well as for four commercially available activated carbons (gas-phase adsorbents Calgon Fluepac-B and BPL 4 x 6; liquid-phase adsorbents Filtrasorb 200 and Carbsorb 30). In addition, adsorption isotherms were developed for inertinite and the two commercially available gas-phase carbons, using methyl ethyl ketone (MEK) as an example compound. Adsorption capacity was measured gravimetrically with a symmetric vapor sorption analyzer (VTI, Inc., Model SGA-100, Kingsville, TX). Also, liquid-phase adsorption experiments were conducted using methyl orange as an example organic compound. The study showed that using inertinite from coal can be beneficially reused as an adsorbent for air or water pollution control, although its surface area and adsorption capacity are not as high as those for commercially available activated carbons.

IMPLICATIONS

The United States currently imports two-thirds of its crude oil, leaving its transportation system especially vulnerable to disruptions in international crude supplies. UT Arlington has developed a liquefaction process that converts coal, abundant in the United States, to crude oil. This work demonstrated that the undissolvable solid coal residual from the liquefaction process, called inertinite, can be converted to an activated carbon adsorbent. Although its surface area and adsorption capacity are not as high as those for commercially available carbons, the inertinite source material would be available at no cost, and its beneficial reuse would avoid the need for disposal.