Optimization of ultrasonic-assisted extraction for determination of polycyclic aromatic hydrocarbons in biochar-based fertilizer by gas chromatography-mass spectrometry

Optimization of a simple, effective, and greener methodology for polycyclic aromatic hydrocarbon extraction from human adipose tissue

Polycyclic aromatic hydrocarbons (PAHs) are environmentally persistent organic pollutants formed during incomplete combustion and pyrolysis processes. Humans are continuously exposed to PAHs which are linked to severe health effects such as diabetes, cancer, infertility, and poor foetal development, amongst others. PAHs are lipophilic compounds prone to accumulating in adipose tissue. Even though adipose tissue is the ideal matrix to assess over time accumulation of lipophilic pollutants, only a few analytical methods have been developed for this matrix. Aiming to reduce the existent gap, a method for the extraction of PAHs from adipose tissue samples using ultrasound-assisted extraction (UAE) was developed. The behaviour of PAHs (retention, adsorption, and volatilization) over several steps of the analytical procedure was studied. Validation tests were performed on the optimized method. PAHs were quantified using a high performance liquid chromatography (HPLC) system equipped with a photodiode array (PDA) and fluorescence (FLD) detector inline. The method achieved a low matrix effect and presents low method detection (MDL) and quantification (MQL) limits, showing suitability for a selective and sensitive determination of PAHs in adipose tissue. The extraction is performed with 0.4 g of adipose tissue and 6 mL of n-hexane and it does not require clean-up afterwards. Additionally, an Eco-Scale score of 74 and an Analytical GREEnness score of 0.66 were obtained. The method achieved is effective, simpler, greener, and easy to perform, being an alternative to conventional extraction methods. Furthermore, this method can be used as a multi-analyte methodology since it has been previously validated by the authors for the analysis of other lipophilic compounds. Naphthalene (Naph), acenaphthene (Ace), fluorene (Flu), phenanthrene (Phe), anthracene (Ant), fluoranthene (Fln), pyrene (Pyr) and benzo[k]fluoranthene (B[k]Ft) were found in all the tested adipose tissue samples.

Tracking 14C-Labeled Organic Micropollutants to Differentiate between Adsorption and Degradation in GAC and Biofilm Processes

Granular activated carbon (GAC) filters can be used to reduce emissions of organic micropollutants via municipal wastewater, but it is still uncertain to which extent biological degradation contributes to their removal in GAC filters. 14C-labeled organic micropollutants were therefore used to distinguish degradation from adsorption in a GAC-filter media with associated biofilm. The rates and extents of biological degradation and adsorption were investigated and compared with other biofilm systems, including a moving bed biofilm reactor (MBBR) and a sand filter, by monitoring 14C activities in the liquid and gas phases. The microbial cleavage of ibuprofen, naproxen, diclofenac, and mecoprop was confirmed for all biofilms, based on the formation of 14CO2, whereas the degradation of 14C-labeled moieties of sulfamethoxazole and carbamazepine was undetected. Higher degradation rates for diclofenac were observed for the GAC-filter media than for the other biofilms. Degradation of previously adsorbed diclofenac onto GAC could be confirmed by the anaerobic adsorption and subsequent aerobic degradation by the GAC-bound biofilm. This study demonstrates the potential use of 14C-labeled micropollutants to study interactions and determine the relative contributions of adsorption and degradation in GAC-based treatment systems.

Extraction of active pharmaceutical ingredients from simulated spent activated carbonaceous adsorbents

Activated carbon (AC) and activated biochar (ABC) are widely used as sorbents for micropollutant removal during water and wastewater treatment. Spent adsorbents can be treated in several ways, e.g., by incineration, disposal in landfills, or reactivation. Regeneration is an attractive and potentially more economically viable alternative to modern post-treatment practices. Current strategies for assessing the performance of regeneration techniques often involve only repeated adsorption and regeneration cycles, and rarely involve direct measurements of micropollutants remaining on the adsorbent after regeneration. However, the use of regenerated adsorbents containing such residual micropollutants could present an environmental risk. In this study, the extraction of eight active pharmaceutical ingredients (APIs) commonly found in treated effluents was evaluated using 10 solvents and sorption onto three different carbon materials. An optimized extraction method was developed involving ultrasonication in 1:1 methanol:dichloromethane with 5% formic acid. This method achieved recoveries of 60 to 99% per API for an API concentration of 2 μg/g char and 27 to 129% per API for an API concentration of 1 mg/g char. Experiments using a mixture of 82 common APIs revealed that the optimized protocol achieved extraction recoveries above 70% for 29 of these APIs. These results show that the new extraction method could be a useful tool for assessing the regenerative properties of different carbon sorbents.

Effects of surfactants on the fractionation, vermiaccumulation, and removal of fluoranthene by earthworms in soil

Vermiremediation, which uses earthworms to remediate polluted soils, is an expanding technology in recently years. Surfactants have been widely used in bioremediation and other remediation technologies. However, the roles of surfactants in vermiremediation have been rarely studied. In this paper, an investigation of the effects of Tween-80 and rhamnolipid surfactant on the fluoranthene fraction distribution, vermiaccumulation, and removal during vermiremediation was conducted. Both Tween-80 and rhamnolipid improved the proportion of the desorbed fraction, bound residual fluoranthene, and correspondingly, proportions of the non-desorbed fraction were reduced. The vermiaccumulation of fluoranthene was significantly elevated by 35-64.1% and 34.5-44.2% by the Tween-80 and rhamnolipid, respectively. The vermiaccumulation of fluoranthene is positively correlated with the proportion of desorbed fraction of fluoranthene. Moreover, Tween-80 and rhamnolipid enhanced the removal of fluoranthene from contaminated soil during vermiremediation by 43.6-189.2% and 14.7-45.6%, respectively. The enhanced removal of fluoranthene was attributed to stimulated microbial degradation and increased vermiaccumulation resulting from the desorption ability of surfactants and earthworm activity. However, the total amount of fluoranthene that accumulated in earthworms was approximately 4-10% of the initial amount in the treatments, which suggested that microbial degradation rather than direct uptake contributed to the fluoranthene removal. The study suggests that the use of surfactants to enhance the efficiency of vermiremediation of polycyclic aromatic hydrocarbons (PAHs) contaminated soils might be feasible, and that surfactants-enhanced vermiremediation is an alternative strategies for treat PAHs contaminated soils.

Efficient simultaneous removal of cadmium and arsenic in aqueous solution by titanium-modified ultrasonic biochar

Simultaneous removal of cations and anions in wastewater has always been a great concerned environmental problem. In this study, a friendly and inexpensive biosorbent to simultaneously remove Cd(II) and As(V) from aqueous solution was synthesized by ultrasonic biochar and nanoscale TiO₂ (TD), and the obtained sorbent was named as BCTD. The maximum sorption capacities of Cd (72.62 mg/g) and As (118.06 mg/g) were much higher than that of other carbon-materials. Both experiments showed that the Cd(II) and As(V) adsorption capacity was above 70% at pH = 5. The Cd(II) and As(V) adsorption on BCTD had a competitive effect in binary metal solutions at above 100 mg/L. The BET, SEM-EDS, FTIR and XPS analyses proved that ultrasonically reacting enhanced the surface area and pore volume of biochar and TD was supported on the biochar surface and inner pores successfully, and the dominant sorption mechanism by BCTD was the ion exchange and complexation.

Use of spent coffee ground biochar as ambient PAHs sorbent and novel extraction method for GC-MS analysis

In recent years, biochar has received a significant amount of attention for its potential beneficial applications in various fields due to its bio-physico-chemical properties. The spent coffee ground biochar was prepared by slow pyrolysis for adsorption of 16-polycyclic aromatic hydrocarbons (PAHs) in ambient air. New materials and extraction methods were developed for PAHs analysis, particularly for low molecular weight (2-4 rings) PAHs, which are likely to evaporate at room temperature. Production and characterization of biochar and its extraction parameters after PAHs adsorption were investigated and optimized. The biochar production at 500 °C provided adequate quality for PAHs adsorption with a 35% yield. An effective clean-up method for biochar was proposed. A new method of PAHs extraction from biochar was developed using 25 mL of a mixture of dichloromethane and 2-propanol (4:1) for 30 min at low temperatures (5-10 °C). A test on the efficiency of the extraction method was carried out and recoveries of 85-104% of PAHs were obtained. The lab-made biochar was also tested for its potential in ambient PAHs sampling and compared with a commercial sorbent (XAD-2). The results revealed that almost the same concentrations of ambient PAHs (ng/m³) were absorbed by both sorbent types, particularly with regard to the 4 ring-PAHs.

Effect of phenanthrene on the physicochemical properties of earthworm casts in soil

Earthworms have been widely studied as bioindicators of soil health for their important role in sustaining soil structure and functions. Many soil contaminants such as phenanthrene have been confirmed to exert adverse effects on earthworms' growth, reproduction, behaviors and biochemical conditions. However, their effects on the properties of earthworm casts have been little studied. In the present study, the effect of different doses of phenanthrene (PHE) (0, 2, 5, 10, 20 mg/kg) on the six physicochemical properties and Fourier transform infrared spectroscopy (FTIR) spectra characteristics of earthworm casts was assessed in artificial soil in a laboratory. 1) Residual concentration of PHE in soils and casts increased with the increasing exposure concentrations and followed the order of casts > soil, concluding that K_ow values are the important factor affecting the distribution of hydrophobic organic contaminants (HOCs) in soil and casts; 2) Earthworms produced casts with improved total organic carbon (TOC) (15-19%), NH₄⁺-N (550-800^%), total available phosphorus (TAP) (300-450%), cation exchange capacity (CEC) (about 15%) and available potassium (AK) (7-12.6%) compared to that in unpolluted soil, indicating that earthworms still have the ability to play the role of ecological engineers even in polluted soil; 3) The sensitivity of different properties of casts to phenanthrene varies, the order of sensitivity being (most sensitive first) NH₄⁺-N ( triggered as 2 mg/kg of exposure concentrations) > AK (5 mg/kg) > Olsen-P (10 mg/kg) > TOC = pH= CEC (no response within the range of exposure concentrations). NH₄⁺-N content in casts shows a clear dose-response relationship when the exposure exceeds 2 mg/kg, indicating that the index might be a potential sensitive biomarker to provide early warning for soil pollution. 4) FTIR spectra showed that the constitution of casts from earthworms in PHE-spiked soil was not significantly alternated. However, FTIR spectra revealed that the concentrations of C-O of polysaccharide in casts increased with the elevated exposure concentrations, indicating that intensities of C-O of polysaccharide at 1032 cm^-1 of casts might be also a potential biomarker for the early-warning of soil pollution. This study advances the knowledge of earthworm ecology in polluted soil, and further extends the scope of earthworm casts as a potential biomarker in soil pollution assessment.

Formulating and Optimizing a Novel Biochar-Based Fertilizer for Simultaneous Slow-Release of Nitrogen and Immobilization of Cadmium

This study aimed to develop and optimize a novel biochar-based fertilizer composed of rice husk biochar and urea–hydrogen peroxide (UHP), which can simultaneously slowly release nitrogen and immobilize cadmium (Cd). Response surface methodology (RSM) was adopted to optimize the fertilizer formulation with the lowest nitrogen release rate. Under the optimized conditions, the cumulative nitrogen release rate of the biochar-based fertilizer was 17.63%, which was significantly lower than that of ordinary fertilizer. Elementary analysis, scanning electron microscopy (SEM) images, and Fourier transform infrared (FTIR) spectroscopy proved that UHP attached to the porous structures of the biochar. The adsorption test showed that the adsorption of Cd onto biochar-based fertilizer quickly reached equilibrium with an equilibrium adsorbing quantity (Qe) of 6.3279 mg·g−1 with an initial concentration of 10 mg·L−1. Compared to original biochar, the Cd immobilization ability of biochar-based fertilizer was significantly better. The adsorption of Cd on biochar-based fertilizer is mainly based on a monolayer adsorption behavior. Finally, improved crop growth was demonstrated by pot experiments, which showed a significant increase in the biomass of cabbage. The concept and findings presented in this study may be used as references in developing a novel biochar-based fertilizer for simultaneously enhancing crop yield and reducing environmental risk.