Agri-food waste biosorbents for volatile organic compounds removal from air and industrial gases - A review

Approximately 1.3 billion metric tons of agricultural and food waste is produced annually, highlighting the need for appropriate processing and management strategies. This paper provides an exhaustive overview of the utilization of agri-food waste as a biosorbents for the elimination of volatile organic compounds (VOCs) from gaseous streams. The review paper underscores the critical role of waste management in the context of a circular economy, wherein waste is not viewed as a final product, but rather as a valuable resource for innovative processes. This perspective is consistent with the principles of resource efficiency and sustainability. Various types of waste have been described as effective biosorbents, and methods for biosorbents preparation have been discussed, including thermal treatment, surface activation, and doping with nitrogen, phosphorus, and sulfur atoms. This review further investigates the applications of these biosorbents in adsorbing VOCs from gaseous streams and elucidates the primary mechanisms governing the adsorption process. Additionally, this study sheds light on methods of biosorbents regeneration, which is a key aspect of practical applications. The paper concludes with a critical commentary and discussion of future perspectives in this field, emphasizing the need for more research and innovation in waste management to fully realize the potential of a circular economy. This review serves as a valuable resource for researchers and practitioners interested in the potential use of agri-food waste biosorbents for VOCs removal, marking a significant first step toward considering these aspects together.

High-performance activation of ozone by sonocavitation for BTEX degradation in water

This work presents a novel advanced oxidation process (AOP) for degradation of emerging organic pollutants - benzene, toluene, ethylbenzene and xylenes (BTEXs) in water. A comparative study was performed for sonocavitation assisted ozonation under 40-120 kHz and 80-200 kHz dual frequency ultrasounds (DFUS). Based on the obtained results, the combination of 40-120 kHz i.e., low-frequency US (LFDUS) with O3 exhibited excellent oxidation capacity degrading 99.37-99.69% of BTEXs in 40 min, while 86.09-91.76% of BTEX degradation was achieved after 60 min in 80-200 kHz i.e., high-frequency US (HFDUS) combined with O3. The synergistic indexes determined using degradation rate constants were found as 7.86 and 2.9 for LFDUS/O3 and HFDUS/O3 processes, respectively. The higher extend of BTEX degradation in both processes was observed at pH 6.5 and 10. Among the reactive oxygen species (ROSs), hydroxyl radicals (HO•) were found predominant according to scavenging tests, singlet oxygen also importantly contributed in degradation, while O2•- radicals had a minor contribution. Sulfate (SO42-) ions demonstrated higher inhibitory effect compared to chloride (Cl-) and carbonate (CO32-) ions in both processes. Degradation pathways of BTEX was proposed based on the intermediates identified using GC-MS technique.

VOCs absorption from gas streams using deep eutectic solvents - A review

Volatile organic compounds (VOCs) are one of the most severe atmospheric pollutants. They are mainly emitted into the atmosphere from anthropogenic sources such as automobile exhaust, incomplete fuel combustion, and various industrial processes. VOCs not only cause hazards to human health or the environment but also adversely affect industrial installation components due to their specific properties, i.e., corrosive and reactivity. Therefore, much attention is being paid to developing new methods for capturing VOCs from gaseous streams, i.e., air, process streams, waste streams, or gaseous fuels. Among the available technologies, absorption based on deep eutectic solvents (DES) is widely studied as a green alternative to other commercial processes. This literature review presents a critical summary of the achievements in capturing individual VOCs using DES. The types of used DES and their physicochemical properties affecting absorption efficiency, available methods for evaluating the effectiveness of new technologies, and the possibility of regeneration of DES are described. In addition, critical comments on the new gas purification methods and future perspectives are included.

Rapid and Direct Assessment of Asphalt Volatile Organic Compound Emission Based on Carbon Fiber Ionization Mass Spectrometry

Due to the complicacy of asphalt fumes, the analytical methods for investigating volatile organic compounds (VOCs) are very limited. In this study, a direct and real-time analysis method based on carbon fiber ionization mass spectrometry (CFI-MS), an ambient mass spectrometric technique, was established and successfully applied in the analysis of asphalt VOCs. The asphalt VOCs can be directly detected in the open atmosphere without the collection step of asphalt fumes, and the mass spectra of one asphalt sample can be obtained in a few seconds in both positive and negative ion modes. By investigating the mass spectral changes of asphalt fumes at different heating temperatures ranging from 50 to 200 °C, the temperature factor of asphalt fume emission was demonstrated in this work. The research results demonstrate that the complexity of asphalt fumes is positively related to the applied temperature. Moreover, the VOCs of saturates, aromatics, resins, and asphaltenes fractions were also analyzed by the direct analysis method. The result shows that aromatics contribute most to the emission of VOCs. In addition, the obtained mass spectra combined with the principal component analysis method show the great potential to quickly screen VOC inhibitors of asphalt materials.

Assessment of the Potential of Using Nanofiltration Polymeric and Ceramic Membranes to Treat Refinery Spent Caustic Effluents

Spent caustic effluents are very challenging due to their very hazardous nature in terms of toxicity as well as their extreme pH (approximately 12–14). Spent caustic has presented a challenge for wastewater treatment in refineries, due to its composition rich in mercaptans, sulfides and other aromatic compounds. To address such problems, membrane filtration was studied using real effluents from Sines Refinery, in Portugal. The present study attempts to assess the potential for spent caustic treatment with nanofiltration (NF) polymeric and ceramic membranes, assessing membrane life expectancy. For that, membrane aging studies in static mode were performed with the polymeric membrane before attempting NF treatment (dynamic studies). A ceramic membrane was also tested for the first time with this type of effluents, though only in dynamic mode. Although the polymeric membrane performance was very good and in accordance with previous studies, its lifespan was very reduced after 6 weeks of contact with spent caustic, compromising its use in an industrial unit. Contrarily to expectations, the ceramic membrane tested was not chemically more resistant than the polymeric one upon direct contact with spent caustic (loss of retention capacity in less than 1 h in contact with the spent caustic). The results obtained suggest that a pH of 13.9 is very aggressive, even for ceramic membranes.

Collection of polycyclic aromatic sulfur heterocycles from asphalt fumes and quantification by an HPLC-DAD method

A chromatographic method is described for the separation and quantification of polycyclic aromatic sulfur heterocycles (PASHs) using liquid chromatography coupled with diode array detection (DAD). The PASHs that were investigated in this study were chosen based on their similarity in molecular weight, volatility and polarity of their PAH analogues. The chromatographic separation of the compounds was optimized, and their analytical characteristics were evaluated. The limits of detection and quantification ranged from 0.05 for 2,3,4,7-tetramethylbenzothiophene to 2.16 μg L-1 for thieno[2,3-b]thiophene and from 0.16 for 2,3,4,7-tetramethylbenzothiophene to 6.53 μg L-1 for thieno[2,3-b]thiophene, respectively. Recoveries ranged from 84.9 for benzo[b]benzo[4,5]thieno[2,3-d]thiophene to 110% for dinaphtho[2,1-b:1',2'-d]thiophene. Intermediate precisions and repeatabilities lie between 1.4 and 3.0%, and 0.3 and 1.7%, respectively. The chromatographic method was applied for determination of PASHs directly in asphalt fumes, which were obtained by heating asphalt samples in a homemade closed system. The mutual interference of PAH analogues was also discussed. The method was successfully used for PASH determination in asphalt samples obtained from three different oil refineries in Brazil.

Evaluation of Reductions in Fume Emissions (VOCs and SVOCs) from Warm Mix Asphalt Incorporating Natural Zeolite and Reclaimed Asphalt Pavement for Sustainable Pavements

Conventional asphalt mixtures used for road paving require high manufacturing temperatures and therefore high energy expenditure, which has a negative environmental impact and creates risk in the workplace owing to high emissions of pollutants, greenhouse gases, and toxic fumes. Reducing energy consumption and emissions is a continuous challenge for the asphalt industry. Previous studies have focused on the reduction of emissions without characterizing their composition, and detailed characterization of volatile organic compounds (VOCs) and semi-volatile organic compounds (SVOCs) in asphalt fumes is scarce. This communication describes the characterization and evaluation of VOCs and SVOCs from asphalt mixtures prepared at lower production temperatures using natural zeolite; in some cases, reclaimed asphalt pavement (RAP) was used. Fumes were extracted from different asphalt mix preparations using a gas syringe and then injected into hermetic gas sample bags. The compounds present in the fumes were sampled with a fiber and analyzed by gas-liquid chromatography coupled to mass spectrometry (GC/MS). In general, the preparation of warm mix asphalts (WMA) using RAP and natural zeolite as aggregates showed beneficial effects, reducing VOCs and SVOCs compared to hot mix asphalts (HMA). The fumes captured presented a similar composition to those from HMA, consisting principally of saturated and unsaturated aliphatic hydrocarbons and aromatic compounds but with few halogenated compounds and no polycyclic aromatic hydrocarbons. Thus, the paving mixtures described here are a friendlier alternative for the environment and for the health of road workers, in addition to permitting the re-use of RAP.

Trapping and preconcentration of volatile organic sulfur compounds in water samples by portable and battery-powered trapping device prior to gas chromatography-sulfur chemiluminescence determination

A simple, portable and battery-powered trapping device (iTrap) consisting of a purification tube, a trapping unit and a miniature air pump was developed for the pre-concentration of volatile organic sulfur compounds (VOSCs). The tested VOSCs, including methanthiol (MT), ethanethiol (ET), dimethyl sulfide (DMS), diethyl sulfide (DES) and dimethyl disulfide (DMDS), were firstly purged from water samples and then in situ pre-concentrated with the iTrap prior to their analysis by thermal desorption gas chromatography coupling with a sulfur chemiluminescence detector (TD-GC-SCD). Twenty-six adsorbents were studied to find the most suitable adsorbent for the efficient pre-concentration of VOSCs. Under optimal conditions, limits of detection of 6, 8, 6, 2 and 3 ng L^-1 were obtained for MT, ET, DMS, DES and DMDS, respectively. The precisions were better than 5.3% (relative standard deviations, RSDs). The iTrap was successfully applied for the analysis of VOSCs in Certified Reference Materials, several surface water, underground water and wastewater samples collected from Pengzhou city, Sichuan, China. Moreover, the VOSCs trapped in the iTrap were much more stable than those directly stored in water samples and the recoveries for all samples could be maintained at acceptable levels (>73%), even their preservation time as long as 8 h.

Absorptive Desulfurization of Model Biogas Stream Using Choline Chloride-Based Deep Eutectic Solvents

The paper presents a synthesis of deep eutectic solvents (DESs) based on choline chloride (ChCl) as hydrogen bond acceptor and phenol (Ph), glycol ethylene (EG), and levulinic acid (Lev) as hydrogen bond donors in 1:2 molar ratio. DESs were successfully used as absorption solvents for removal of dimethyl disulfide (DMDS) from model biogas steam. Several parameters affecting the absorption capacity and absorption rate have been optimized including kinds of DES, temperature, the volume of absorbent, model biogas flow rate, and initial concentration of DMDS. Furthermore, reusability and regeneration of DESs by means of adsorption and nitrogen barbotage followed by the mechanism of absorptive desulfurization by means of density functional theory (DFT) as well as FT-IR analysis were investigated. Experimental results indicate that the most promising DES for biogas purification is ChCl:Ph, due to high absorption capacity, relatively long absorption rate, and easy regeneration. The research on the absorption mechanism revealed that van der Waal interaction is the main driving force for DMDS removal from model biogas.

Effective degradation of sulfide ions and organic sulfides in cavitation-based advanced oxidation processes (AOPs)

The paper presents the results of investigations on the effectiveness and reaction rate constants of the oxidation of sulfide ions and organic sulfides in real industrial effluents from the production of bitumens (2000 mg S^2- L^-1) using hydrodynamic and acoustic cavitation. The content of the effluents was analysed in terms carbon disulfide, dimethyl sulfide, and di-tert-butyl disulfide concentration. A possibility of complete oxidation of sulfides by cavitation alone as well as by its combination with external oxidants such as hydrogen peroxide, ozone or peroxone was demonstrated. The oxidation time for the most effective processes is as little as 15 min. Due to the presence of sulfide ions, the effluents from the production of bitumens were oxidized at a strongly alkaline pH. The results of this study reveal the advantage of performing advanced oxidation processes (AOPs) at a basic pH. The effective degradation of sulfide ions enables performance of further degradation of organic contaminants at an acidic pH, ensuring high efficiency of treatment based, for example, on the Fenton reaction without the risk of release of hydrogen sulfide to the atmosphere. The results of this research are applicable to all kinds of caustic effluents for which the lack of possibility of pH adjustment limits their efficient treatment.

Application of cyanated asphaltenes in gas-phase adsorption processes for removal of volatile organic compounds

The paper presents an innovative, chemically modified (methylcyanated) asphaltene-based adsorbent that can be an interesting low-cost alternative for traditional adsorbents. Adsorption properties of adsorbents were examined by inverse gas chromatography technique, adsorption isotherms, and breakthrough curves. A significant increase in retention volume for pyridine, 2-pentanone, nitropropane, toluene, and 1-butanol was observed. Rohrschneider–McReynolds constants revealed an increase in strength of interactions as a result of the modification, especially in strong proton–acceptor interaction (by a factor of 4.6). The surface-free energy of asphaltene adsorbents increased from 136.71 to 169.95 mJ m−2 after modification. It is similar to the surface-free energy of silica or alumina. Moreover, modified adsorbent shows very high adsorption potential for pyridine. Adsorption isotherms revealed that monolayer adsorption capacity for pyridine increased 1.5 times after modification. Breakthrough curves of pyridine indicate that chemical modification increased the adsorption capacity, removal efficiency, and throughput. Scale-up calculations revealed that adsorption column packed with modified asphaltene adsorbent would be almost two times smaller compared to a column packed with unmodified one.

Graphic abstract

Highly effective degradation of selected groups of organic compounds by cavitation based AOPs under basic pH conditions

Cavitation has become on the most often applied methods in a number of industrial technologies. In the case of oxidation of organic pollutants occurring in the aqueous medium, cavitation forms the basis of numerous advanced oxidation processes (AOPs). This paper presents the results of investigations on the efficiency of oxidation of the following groups of organic compounds: organosulfur, nitro derivatives of benzene, BTEX, and phenol and its derivatives in a basic model effluent using hydrodynamic and acoustic cavitation combined with external oxidants, i.e., hydrogen peroxide, ozone and peroxone. The studies revealed that the combination of cavitation with additional oxidants allows 100% oxidation of the investigated model compounds. However, individual treatments differed with respect to the rate of degradation. Hydrodynamic cavitation aided by peroxone was found to be the most effective treatment (100% oxidation of all the investigated compounds in 60 min). When using hydrodynamic and acoustic cavitation alone, the effectiveness of oxidation was diversified. Under these conditions, nitro derivatives of benzene and phenol and its derivatives were found to be resistant to oxidation. In addition, hydrodynamic cavitation was found to be more effective in degradation of model compounds than acoustic cavitation. The results of investigations presented in this paper compare favorably with the investigations on degradation of organic contaminants using AOPs under conditions of basic pH published thus far.

Effective method of treatment of effluents from production of bitumens under basic pH conditions using hydrodynamic cavitation aided by external oxidants

Utilization of cavitation in advanced oxidation processes (AOPs) is a promising trend in research on treatment of industrial effluents. The paper presents the results of investigations on the use of hydrodynamic cavitation aided by additional oxidation processes (O₃/H₂O₂/Peroxone) to reduce the total pollution load in the effluent from the production of bitumens. A detailed analysis of changes in content of volatile organic compounds (VOCs) for all processes studied was also performed. The studies revealed that the most effective treatment process involves hydrodynamic cavitation aided by ozonation (40% COD reduction and 50% BOD reduction). The other processes investigated (hydrodynamic cavitation+H₂O₂, hydrodynamic cavitation+Peroxone and hydrodynamic cavitation alone) ensure reduction of COD by 20, 25 and 13% and reduction of BOD by 49, 32 and 18%, respectively. The results of this research revealed that most of the VOCs studied are effectively degraded. The formation of byproducts is one of the aspects that must be considered in evaluation of the AOPs studied. This work confirmed that furfural is one of the byproducts whose concentration increased during treatment by hydrodynamic cavitation alone as well as hydrodynamic cavitation aided by H₂O₂ as an external oxidant and it should be controlled during treatment processes.

Temperature-programmed multicapillary gas chromatograph microcolumn for the analysis of odorous sulfur pollutants

We report the fabrication and performance of a silicon-on-glass micro gas chromatography eight-capillary column based on microelectromechanical systems technology that is 50 cm long, 30 μm wide, and 300 μm deep. According to the theory of a gas chromatography column, an even gas flow among different capillaries play a vital role in the peak broadening. Thus, a flow splitter structure is designed by the finite element method through the comparison of the velocity distributions of the eight-capillary columns with and without splitter as well as an open tubular column. The simulation results reveal that eight-capillary column with flow splitters can receive more uniform flow velocity in different capillaries, hence decreases the peak broadening and in turn increases the separation efficiency. The separation experiment results show that the separation efficiency of about 22 000 plates/m is achieved with the chip column temperature programmed for analysis of odorous sulfur pollutants. This figure is nearly two times higher than that of the commercial capillary column coated the similar stationary phase. And the separation time of all the components in the microcolumn is less than 3.8 min, which is faster than the commercial capillary column.

Method for the determination of carboxylic acids in industrial effluents using dispersive liquid-liquid microextraction with injection port derivatization gas chromatography-mass spectrometry

The paper presents a new method for the determination of 15 carboxylic acids in samples of postoxidative effluents from the production of petroleum bitumens using ion-pair dispersive liquid-liquid microextraction and gas chromatography coupled to mass spectrometry with injection port derivatization. Several parameters related to the extraction and derivatization efficiency were optimized. Under optimized experimental conditions, the obtained limit of detection and quantification ranged from 0.0069 to 1.12μg/mL and 0.014 to 2.24μg/mL, respectively. The precision (RSD ranged 1.29-6.42%) and recovery (69.43-125.79%) were satisfactory. Nine carboxylic acids at concentrations ranging from 0.10μg/mL to 15.06μg/mL were determined in the raw wastewater and in samples of effluents treated by various oxidation methods. The studies revealed a substantial increase of concentration of benzoic acids, in samples of wastewater after treatment, which confirms the need of carboxylic acids monitoring during industrial effluent treatment processes.