Hydrochars as Emerging Biofuels: Recent Advances and Application of Artificial Neural Networks for the Prediction of Heating Values

In this study, the growing scientific field of alternative biofuels was examined, with respect to hydrochars produced from renewable biomasses. Hydrochars are the solid products of hydrothermal carbonization (HTC) and their properties depend on the initial biomass and the temperature and duration of treatment. The basic (Scopus) and advanced (Citespace) analysis of literature showed that this is a dynamic research area, with several sub-fields of intense activity. The focus of researchers on sewage sludge and food waste as hydrochar precursors was highlighted and reviewed. It was established that hydrochars have improved behavior as fuels compared to these feedstocks. Food waste can be particularly useful in co-hydrothermal carbonization with ash-rich materials. In the case of sewage sludge, simultaneous P recovery from the HTC wastewater may add more value to the process. For both feedstocks, results from large-scale HTC are practically non-existent. Following the review, related data from the years 2014–2020 were retrieved and fitted into four different artificial neural networks (ANNs). Based on the elemental content, HTC temperature and time (as inputs), the higher heating values (HHVs) and yields (as outputs) could be successfully predicted, regardless of original biomass used for hydrochar production. ANN3 (based on C, O, H content, and HTC temperature) showed the optimum HHV predicting performance (R2 0.917, root mean square error 1.124), however, hydrochars’ HHVs could also be satisfactorily predicted by the C content alone (ANN1, R2 0.897, root mean square error 1.289)

Assessment of Orange Peel Hydrochar as a Soil Amendment: Impact on Clay Soil Physical Properties and Potential Phytotoxicity

Purpose: The main objectives of this work were the following: (1) to investigate the applicability of orange peel hydrochar as a soil amendment for improving the physical properties of a compacted, clay soil and (2) to study the growth of maize on substrates composed of clay soil and hydrochar and determine any potential phytotoxic effects. Methods: The effect on soil’s bulk density (BD), aeration, water holding capacity (WHC), and hydraulic conductivity were examined with hydrochar additions of 5, 10 and 15% (w/w) and determined by conventional laboratory methods. Potential phytotoxic effects were determined through the Zucconi germination index on fresh, diluted and 4-week old undiluted hydrochar extracts. The effect of hydrochar on maize growth was studied in clay soil (as reference), clay soil with 5% (w/w) fresh hydrochar, clay soil with 5% (w/w) of 4-week-old hydrochar and clay soil with 5% (w/w) biochar (for comparison). Results: At an application rate of 5% (w/w) hydrochar, the bulk density was reduced from 1.35 to 1.22 g/cm3, the air-filled porosity was increased from 33 to 37% and the saturated hydraulic conductivity from 0.96 to 1.01 cm/h. The water holding capacity remained practically unchanged, however it was considerably reduced at higher application rates. The seed germination test indicated strong phytotoxicity of the fresh, undiluted hydrochar extract, which was reduced when the extract was diluted or the hydrochar allowed to mature for 4 weeks. The pot tests indicated that hydrochar did not improve the yield of maize, probably due to the presence of phytotoxic substances. Conclusions: This study demonstrated a new valorization pathway for a significant agricultural waste. Additionally, it proved the applicability of orange peel hydrochar for improving the physical properties of clay soil. However, due to phytotoxic effects, further work is required before a field application is considered. © 2018 Springer Nature B.V

Ultrasonic-assisted extraction of 10-deacetylbaccatin III from Taxus baccata L.: optimization using response surface methodology

Kayan, Berkant ( Aksaray, Yazar )The ultrasonic-assisted extraction of 10-deacetylbaccatin III from needles of Taxus baccata L. was evaluated using ethanol and methanol as solvents. The effects of temperature, extraction time and particle size were determined by response surface methodology. In the case of ethanol, the optimum values of temperature, extraction time and needle particle size were determined as 44.8 °C, 40.1 min and 113 μm, whereby 102 mg/kg yield could be obtained. For methanol, the respective values were 43.7 °C, 43 min and 114.6 μm, which yielded 112 mg/kg. The results showed that at the optimum operating conditions, it was possible to obtain a reasonable yield using this extraction process. Liquid chromatography–electrospray ionization tandem mass spectrometry (LC–MS/MS) was employed to investigate the fragments of the taxanes from T. baccata

Degradation, solubility and chromatographic studies of Ibuprofen under high temperature water conditions

*Akay, Sema ( Aksaray, Yazar ) *Öztürk, Serpil ( Aksaray, Yazar )Ibuprofen (IBP) is an emerging environmental contaminant having low aqueous solubility which negatively affects the application of advanced oxidation and adsorption processes. It was determined that as the temperature increased to 473 K, the mole fraction solubility increased considerably from 0.02 × 10−3 to 212.88 × 10−3 (10600-fold). Calculation of the thermodynamic properties indicated an endothermic process, ΔsolH > 0, with relatively high ΔsolS values. Spectroscopic, thermal and chromatographic analyses established the IBP stability at subcritical conditions. In the second part of the study, the degradation of IBP in H2O2-modified subcritical was studied and the effect of each process variable was investigated. The optimum degradation of 88% was reached at an IBP concentration of 15 mg L−1, temperature of 250 °C, 105 min treatment time and 250 mM H2O2. The process was optimized by response surface methodology and a mathematical model was proposed and validated. Temperature was determined as the most influential parameter, followed by H2O2 concentration. At temperatures higher than 230 °C, a small but noticeable reduction in degradation % suggested that the OH· radicals are consumed at a higher rate than they are produced, through side reactions with other radicals and/or IBP by-products. Finally, potential by-products were determined by gas chromatographic-mass spectrometric analysis and potential by-products were proposed

Microplastics as carriers of hydrophilic pollutants in an aqueous environment

Plastic materials such as polyethylene (PE), polyvinyl chloride (PVC), and polyamide nylon 6 (PN6) are extensively used worldwide. Significant quantities end up in the environment as waste, which gradually deteriorate and may travel for long distances. In this study, the capacity of these microplastics to sorb RR 120, an anionic dye commonly found in textile wastewaters, was investigated. PN6 showed the highest sorption capacity of 4.80 mg g−1, at a dose of 0.4 g and pH 2, whereas increasing the dose of the microplastic resulted in a gradual decrease of the sorption capacity for all materials. Increasing the dye concentration, resulted in higher sorption capacities. The FTIR analysis of the microplastics before and after sorption of RR 120, indicated no chemical bonding pointing out the absence of covalent bonds with specific surface groups of the microplastics in the sorption of RR 120. A plausible explanation for the highest sorption capacity of PN6 is the presence of N and O, which can readily form H bonds with the hydroxyl groups of RR 120

Assessment of Biochar Produced by Flame-Curtain Pyrolysis as a Precursor for the Development of an Efficient Electric Double-Layer Capacitor

Pine tree biochar produced by flame-curtain pyrolysis, an inexpensive and simple pyrolysis methodology, was used as the starting material for KOH-activated carbon. Flame-curtain pyrolysis is a simple, low-technology methodology that can be performed by non-specialized personnel. The elemental analysis of the biochars highlighted the high reproducibility of the process. The N2 adsorption isotherms indicated that KOH activation was effective for the preparation of high-surface-area activated carbons from the biochar. The BET specific surface area increased with the quantity of KOH added in the activation process, achieving a maximum value of 3014 m2 g−1 at 85.7 wt.% of KOH addition. The adsorption isotherms of all samples were IUPAC type I, establishing their microporous nature. Results from the Mikhail–Brunauer (MP) method and αs plot indicated that the pore size distribution became wider and the pore volume increased as the KOH content increased. The measured capacitance values followed the same dependence on KOH content. The maximum capacitance value at 1 mV s−1 was determined as 200.6 F g−1 for the sample prepared at 75 wt.% of KOH addition. Therefore, pine tree biochar prepared by simple pyrolysis equipment is a suitable precursor for the development of an electric double-layer capacitor

Adsorption of Malachite Green on Fe-modified biochar: Influencing factors and process optimization

WOS: 000403572000038Paper sludge and wheat husk biochar was converted to a Fe-composite through a simple co-precipitation process and its adsorption behavior was tested against an emerging pollutant, Malachite Green (MG). Response surface methodology was employed to determine the optimum experimental conditions and the interactions between pH, initial MG concentration, temperature and treatment time. The maximum adsorption percentage obtained experimentally was 97.1%, whereas the Box-Behnken design predicted a maximum adsorption of 98%, at pH 6.16, initial MG concentration of 6.56 ppm, temperature of 34.75 degrees C and treatment time of 22 min. Compared with the original biochar, the Fe-modified sample improved the adsorption of MG by similar to 34%. The adsorption mechanism followed the Langmuir model (q(max) = 172.3 mg/g, correlation coefficient 0.960) and the kinetics of the process were best described by the pseudo-second-order model (correlation coefficient 0.9818), although boundary layer effects were also observed

Assessment of a Pd-Fe3O4-biochar nanocomposite as a heterogeneous catalyst for the solvent-free Suzuki-Miyaura reaction

The objective of this study was the development of a novel, biochar-based Pd nanocatalyst and its evaluation for the promotion of the Suzuki-Miyaura coupling reaction. The Fe3O4-Pd-biochar composite was successfully characterized through a range of spectroscopic and elemental analysis techniques. Its catalytic activity was initially assessed using p-NO2C6H4I as a model reactant and later for the production of biaryls from a wide range of aryl halides, under microwave irradiation and solvent-free conditions. The optimum yield of 99% was obtained at a catalyst dosage of 8 mg, microwave irradiation of 400 W, 6 min residence time, using K2CO3 as the base. Furthermore, the catalyst promoted the Suzuki-Miyaura reaction of aryl iodides and bromides (yields in the range of 88-97 and 86-97%, respectively), but was less successful for aryl chlorides (yields 78-83%). The presence of Fe3O4 allowed for the quick recovery of the catalyst, whereas repeated runs established its recyclability

Adsorption of Arsenic on Fe-Modified Biochar and Monitoring Using Spectral Induced Polarization

This work demonstrates the potential of Fe-modified biochar for the treatment of arsenic (As) simulated wastewater and the monitoring of adsorption in real-time. Specifically, we propose the utilization of date-palm leaves for the production of biochar, further modified with Fe in order to improve its adsorption function against inorganic pollutants, such as As. Both the original biochar and the Fe-modified biochar were used for adsorption of As in laboratory batch and column experiments. The monitoring of the biochar(s) performance and As treatment was also enhanced by using the spectral induced polarization (SIP) method, offering real-time monitoring, in addition to standard chemical monitoring. Both the original and the Fe-modified biochar achieved high removal rates with Fe-modified biochar achieving up to 98% removal of As compared to the 17% by sand only (control). In addition, a correlation was found between post-adsorption measurements and SIP measurements