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A simple electrochemical approach has been strategically developed for in situ generations of ZnO nanoparticles using Zn rods as electrodes and hydrogen peroxide as the oxidant without the formation of any by-product. These ZnO nanoparticles were extended for remediation of pollutants present in paper mill effluents, and separation efficiency was found to be above 90% for hydrocarbons, 92% for lignin, 99% for phenol, and 93% of chemical oxygen demand (COD), as confirmed by gas chromatography-mass spectrometry and COD analysis. It was also observed that the experimental setup could successfully remove 99% of the color from the sample. These ZnO nanoparticles have been proven in the past to be antibacterial and were explored for its ability to inhibit the growth of both Gram-positive and Gram-negative bacteria in the effluent samples after the removal of toxic pollutants. Therefore, we proposed an electrochemical reaction for the in situ synthesis of ZnO nanoparticles for remediation of paper mill effluent as well as inhibit the bacterial growth in the treated effluent sample.

In this research, simultaneous quantification of cysteine (Cys) and histidine (His) using a paper-based sensor was investigated for the first time. A microfluidic paper-based sensor is a promising amino acid determination tool due to its low cost, low sample consumption, and fast analysis and is easy to make. We used SBA-15 as porous materials that are crystalline compounds formed with surfactants and TEOS as a silica source. The SBA-15 sample was characterized by X-ray diffraction, Fourier transform infrared, and scanning electron microscope techniques. The microfluidic paper-based sensors were fabricated using a wax pen, and the mesoporous SBA-15 modified filter paper. The fabricated sensors for Cys and His determination are operated based on an indicator-displacement assay. A comparative determination study of Cys and His on the sensors was carried out. The results illustrated that the addition of silica nanoporous material led to an immediate and uniform color change. The sensors were successfully exploited in the simultaneous determination of urinary Cys and His levels, thus providing the potential opportunity for clinical diagnosis. The linear range of 1.0 to 90.0 μM and 1.0 to 100 μM for His and Cys was obtained from the calibration data. The detection limits were also calculated (S/N = 3) for His and Cys of 0.5 μM and 1.5 μM, respectively. The proposed method showed a good agreement with the results achieved by a standard method.

Given the effects of metal ions on environment and human’s health, it is very important to identify them in aqueous solutions. Core–shell structures can be used to identify metal ions through preparation of paper sensors. In the present research, ZnO@ZnS nanoparticles with core–shell structure were prepared through two-step low temperature green synthesis process using aloe vera and lettuce extracts. The synthesized nanoparticles were characterized by Fourier transform infrared, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy analyses. The results of FTIR and XRD analyses confirmed successful formation of ZnO@ZnS core–shell structures. Micrographs of the synthesized particles also showed flaky shapes with sharp edges and random orientations. Size range of core–shell nanoparticles varied between 20 and 70 nm. Then, the solution containing green synthesized ZnO@ZnS nanoparticles was distributed onto the papers and after drying at room temperature was used as paper sensors to identify Pb2+ and Fe2+ ions. The color intensity of the sensors changed due to contact with solutions containing different concentrations of Pb2+ and Fe2+ ions (75–1500 μM). In addition, increasing concentration of ions increased color intensity of sensors and the relationship between color intensity and ion concentration was expressed by related equations. Therefore, it was possible to determine the concentration of lead and iron ions according to the color intensity. Comparison between the performance of the sensors exposed to the solutions prepared from deionized water and ZayandehRud River water showed an acceptable error of up to 5%. The results of XRD analysis on paper sensors after contacting with Pb2+ and Fe2+ ions confirmed the formation of PbS and FeS.

Glucose is a typical diagnostic marker of diabetes mellitus but it may be also helpful during diagnosis of some types of poisoning, immunological disorder or long-term stress at hospitalized patients. Diagnosis of diabetes mellitus in time is indispensable for prevention of life-threatening complication and so, accurate and easy device for non-invasive and accurate self-diagnosis is necessary. Simple assay based on filter paper with chitosan layer and with immobilized enzymes glucose oxidase and peroxidase and phone camera detection has been proposed for home-care glucose detection in urine. Data were processed in RGB (red–green–blue) color model when blue color channel showed the best sensitivity to changing glucose concentrations. Assay exerted linear regression from 0 to 4 mmol/l and limit of detection was set to be 166 µmol/l. Assay was not influenced by any interfering substances including maltose, sucrose, sorbitol or fructose or by urine matrix substance such as bovine serum albumin, ascorbic acid, uric acid or urea. Measurement of glucose from spiked urine samples reveals also no influence of the matrix on the assay. Long-term stability was measured and filter papers coated by enzymes showed excellent stability for at least 9 weeks without any special treatment or package. In comparison with differently modified filter paper, filter paper with both chitosan and enzymes showed the best sensitivity to changing glucose concentration. In a conclusion, simple (phone camera detection) and fast (3-min reaction) assay for quantitative detection of glucose from urine was optimized.

The X-ray diffraction internal standard method can quantitatively determine the ash content of paper, but the requirements for the experimental environment are high, the determination is not convenient and the cost is high, and it is difficult to be widely used in the papermaking enterprises. In order to determine the total ash and its components of the single filler paper samples, and meet the ash determination requirements of papermaking enterprises, the continuous X-ray method is proposed. In this paper, an X-ray tube is used as the radiation source and an ionization chamber is used as the detector. Through polynomial fitting of the total ash and voltage logarithm ratio of the single filler paper samples, the mathematical model of total ash is established; the total ash and its components content of paper are calculated according to the mathematical model of total ash and the Beer–Lambert law deformation formula; the total ash and its components content of paper are verified by the burning method. The research results show that the total ash error of the single filler paper samples is less than 4%, and the ash component error is less than 5%.

The properties of crystal violet lactone (CVL), currently the most commonly used color developer in carbonless papers, were studied. The hypothesis that CVL exhibits different properties in the carbonless and in the office papers was verified, as well as the CVL´s ability to luminesce in the IR region. Furthermore, the impact of thermal and light aging on some physical and chemical properties of the copies was observed. The changes were monitored by observing the IR luminescence at several wavelength ranges. Visual, colorimetric and structure differences between the copies made on the carbonless and the office paper were analyzed. The surface structure of the carbonless paper was analyzed using SEM–EDS.

This article exhibits an innovative, low-cost, and environmentally friendly sensor for identifying aqueous chemicals. The sensor is able to distinguish between different varieties of chemicals including acids, bases, deionized water, and solvents. The sensing device can be used in a wide range of industrial applications that require low-cost, accurate methods of chemical detection. The device can identify different chemicals based on changes in the electrical resistance of graphite which is used as a sensing element. A graphite line was drawn on a sheet of paper using a pencil that was used as the test strip and placed in a custom-made test fixture, providing a controlled environment once the graphite test strip was in contact with electrical contacts mounted in the fixture. The electrical contacts of the fixture were connected to a data acquisition device which measured and recorded voltage outputs using LabVIEW software. The data collected were then used to compute the electrical resistance. The solvent analysed in this research was isopropyl alcohol. The acids analysed were nitric acid, sulphuric acid, hydrochloric acid, and hydrogen peroxide. The base analysed was ammonium hydroxide. Tests were performed by placing two droplets of each chemical onto the paper through an inlet hole located at the top of the test fixture. All tests were performed at a constant temperature. The electrical voltage was recorded every millisecond once the chemical was dropped onto the test strip through the hole in the test fixture. Electrical resistance versus time plots displayed a unique curve for each chemical analysed which may be used for chemical identification.

In this study, two important biomarkers, namely glucose and uric acid, were detected in different biological fluids using a highly sensitive and selective chitosan-/nano-based electrochemical microfluidic paper-based analytical device (µPAD). A graphite/chitosan/polyethylene glycol (PEG) mixture was used as bare working electrode and counter electrode with silver ink being used as quasi-reference electrode. Graphene, multiwall carbon nanotubes, and Fe3O4 nanoparticles were used to improve sensitivity as well as selectivity of the working electrodes. The developed chitosan-/nano-based microfluidic analytical system showed apparent redox peaks, and all the three types of nanomaterials improved the performance of the bare graphite/chitosan/PEG electrode with the Fe3O4-modified electrode exhibiting the sharpest signals with the highest selectivity. The linear ranges of glucose and uric acid were 0.01–30 mM and 0.05–15 mM, respectively, where the limits of detection (LOD) were 5 µM and 20 µM for glucose and uric acid, respectively. In comparison with most of previous data reported on μPADs and due to high surface area/volume ratio of NPs and faster electron transfer promoted by chitosan and NPs, the better LODs were found in the current study. The fast, efficient, and low-cost µPADs were successfully applied to highly sensitive and selective detection of glucose and uric acid in serum and urine samples and noninvasive glucose detection in tear samples.

Studying of paper carriers of information has become increasingly important in forensic practice. This is caused by growing number of bogus or in other manner fraudulently alternated documents. An identification of individual paper sheets and studying their differences are the parts of forensic analysis of multiple sheets documents. This paper focuses on the possibilities of processing of mathematical and statistical data obtained by measurements of FT-IR spectral characteristics of individual paper sheets in a studied document. The spectral data were used to create data matrix which contains values of absorbance and interval of wavenumber. The method of differentiation is based on the comparison of maximum absorbance values within the range of wavenumbers from 1562 to 1215 cm−1. This spectrum range is specific in occurrence of absorption bands that belong to calcium carbonate CaCO3—an element of paper added into it in relatively high amounts in the form of filler which content or percentage occurrence may be different considering to the paper producer or production technology. Based on the above-said, the paper sheets originating from different producers or from various production technology units can be differentiated one from another using a robust statistical analysis.

Acid dissociation constant is an important chemical characteristic of organic and inorganic compounds and it affects both chemical properties and biological activities of the molecules. Herein, a very simple, fast and cost-effective method based on microfluidic technology has been reported for colorimetric determination of acidity constants. The designed device works based on pH-metric titration of colorful indicators followed by colorimetric measurements by a smart phone mobile device or a flatbed scanner. So, it does not need sophisticated instrumentation and is accomplished in a very short time (about 1 min). All titration steps are transferred on a star-like designed µPAD device: (1) spotting 0.3 µL buffers of different pHs at the end of the channels (reaction zones), (2) spotting a 30 µL portion of the indicator on the center of µPAD followed by movement of indicator solution toward the reaction zone by capillary action of the paper. The measured color change of the indicators at the reaction zone is fitted to the Henderson–Hasselbalch equation, through which acidity constants are calculated. The performance of the device was evaluated by measuring acidity constant of 4 indicators including bromothymol blue, bromocresol green, bromocresol purple and phenolphthalein. A very close agreement was achieved between those measured by the suggested device here and the previously reported values. The reproducibility of this method was lower than 5% for relative standard deviation of three replicate measurements.

This work is aimed at a selection of yeast strains suitable for simultaneous saccharification and fermentation of waste paper. The waste paper, as a lignocellulosic material, represents an unconventional source for the production of ethanol which is a promising alternative fuel. The yeast strains Saccharomyces cerevisiae and Pichia kudriavzevii produced the highest amounts of ethanol at 30 °C and were also resistant at 40 °C during the first 92 h of fermentation. These two strains were immobilized by entrapment into poly(vinyl alcohol) hydrogel lens-shaped particles LentiKats®. The immobilized S. cerevisiae was a better ethanol producer and retained higher metabolic activity in repeated batch fermentations than P. kudriavzevii. The immobilized S. cerevisiae was also suitable for a long-term storage, with 23% decrease in the ethanol production ability after 1-year storage of yeast cells.

A method was developed for the fabrication of microfluidic paper-based analytical devices (μPAD). This method was based on the silanisation of cellulose in filter paper using alkyltrimethoxysilane coupled with UV radiation. The filter paper sheet was hydrophobised by immersion in an octadecyltrimethoxysilane/heptane (OTMS/heptane) solution (0.25 vol. %) containing 5 vol. % of ethyl acetate (EtOAc). The hydrophobic-hydrophilic contrast was generated on the filter paper after the hydrophobised paper sheet was exposed to UV light with a metal mask creating the desired pattern on the sheet. The exposed area was oxidised to create a hydrophilic area, while the hydrophobic area was protected by the metal mask. The optimal conditions for the fabrication of μPAD were studied; these included ethyl acetate concentration (CEtOAc), immersion time, octadecyltrimethoxysilane concentration (COTMS) and exposure time. This method is cost-effective and simple. In addition, different functional groups could be further grafted for various assay purposes. To demonstrate the feasibility of the μPAD in analytical applications, a flower-shaped μPAD with eight channels and eight detection units was fabricated and used to determine the nitrite content in pickled vegetables. The nitrite content (124 µg g−1) in the sample determined by this method compared favourably with that measured using a standard method (137 µg g−1).

The development of a sensor based on the functionalization of common filter paper with deferoxamine (DFO) is proposed with the prospect to produce a solid phase for iron(III) and vanadium(V) sensing. The main features of this sensor are the simplicity of operation, good sensitivity and feasible applicability to real samples without the need of pre-treatment procedures. DFO was selected not only for it is easily anchored to the solid support, but also because it forms colored complexes with iron(III) and vanadium(V); hence, the developing of a simple colorimetric sensor can be considered. In particular, an innovative and economic way to perform colorimetric measurements using a desktop scanner is described. A complete characterization of the functionalized material is also reported.

Hornification is the loss of fiber wall swelling which is detrimental to subsequent recycling resulting from drying. It is known that dried fibers lose their conformability and swelling capacity. The effect of recycling treatment on the swelling ability of hardwood bleached kraft pulp fibers was determined. Modelling paper recycling, sheets were recycled using heat treatment (23°C, 60°C, 100°C). The results were compared with those for natural fibers from bleached kraft pulp. Swelling kinetics of sheets was measured by a modified method monitoring interactions of pulp with water. Swelling ability decreased during the recycling in comparison with never-recycled pulp at all temperatures. Recycling of sheets caused only small changes in the cupri-ethylene-diamine viscosity, however, the water retention value decreased considerably.

There are large numbers of paper cultural relics in China, the country where paper making was invented. However, the paper relics have not been adequately protected so they are at risk of ageing, damage and disappearance. In order to better protect the paper relics, modified carboxymethyl cellulose/Si/polyacrylate protective materials were prepared with acrylicresin and modified carboxymethyl cellulose which has a good affinity with the paper and modified silica, improving the mechanical strength and ability to withstand weathering. The modified CMC/Si/polyacrylate protective material was analysed using infrared spectroscopy, transmission electron microscopy, differential scanning calorimetry and other performance-testing devices. The surface morphology of the paper samples was analysed using scanning electron microscopy. The protective material so prepared was evaluated by subjection to accelerated ageing (dry heat treatment). The results showed the protective material films to have good hydrophobicity, acid/alkali resistance and mechanical strength. When the content of SiO2 is 6 mass %, the protective material has an excellent comprehensive performance. The results of the ageing test reveal that the prepared material can effectively slow down the ageing rate. The prepared material is suited to the protection of paper cultural relics.

A method for the determination of the moisture content in cigarette papers using solvent extraction followed by gas chromatographic analysis was developed. Optimal extraction conditions, including the agitation method, solvent and extraction time, as well as optimal gas chromatographic parameters, such as the internal standard, were investigated. The maximum degree of moisture extraction was achieved when samples were soaked in 20 mL of ethanol containing 0.5 mL L−1 of isopropanol as an internal standard for 50 min under ultrasonic agitation. The method showed good linearity over the concentration range from 0.26 mass % to 10 mass % of the moisture content with a correlation coefficient of 0.99998. The recovery (102.1–109.3 %) and precision (relative standard deviation: 1.64 %) of the method were examined by analyzing various cigarette paper samples. The method was successfully applied to different types of paper and it exhibits superior accuracy and high efficiency compared with the existing methods of moisture determination.

The aim of this study was to assess the role and proportional representation of depolymerisation and thermoxidation reaction paths in the systems paper/gum arabic (GA)/historical ink during various accelerated ageing methods. The historical inks under study are iron-gall, bistre, and sepia. The results indicate that thermoxidation represents only a minor reaction path in the ageing of paper/GA/ink systems except for the iron-gall ink and the light-thermal method of accelerated ageing. The iron-gall ink accelerates both reaction paths of ageing, i.e. thermoxidation and depolymerisation; in this case, thermoxidation might become the prevailing degradation reaction path. For the sepia ink, an anti-depolymerisation stabilising effect in thermal methods of ageing has been detected. Considering the thermoxidation reaction path, the results even suggest that a compound preventing thermoxidation is formed during the thermally accelerated ageing in air and in 100 mg L−1 of NO2. In the light-thermal ageing, the most stable sample is the Whatman paper (W)/GA/bistre ink.

Raman spectroscopy and surface enhanced Raman spectroscopy were used to examine 14 blue inks obtained from commercially available stationery. Standard colouring agents in the inks: β-phase of phtalocyanine blue PB15 and some homologues of the methyl violet class, were identified. Surface enhanced Raman spectra were recorded on a firm heterostructure of silver/nanocrystalline diamond/silicon constituting an active substrate providing the possibility to write directly on the surface. Based on the differences in traditional and surface enhanced Raman spectra, two inks were identified unambiguously, the remaining inks were categorised into three groups exhibiting common spectral features. Despite their similarity, surface enhanced Raman spectra exhibited soft variations enabling discrimination of the inks, thus proving the usefulness of the method.

During natural ageing, paper undergoes colour changes and becomes brittle. It is mainly due to the degradation of cellulose, the main component of paper fibres. From the viewpoint of conservation/protection of paper-based information carriers, as well as of the utilisation of secondary fibres, knowledge of the impact of a decrease of the degree of polymerisation (DP) of cellulose on mechanical properties of paper becomes of key importance. In this paper, correlations between the decrease of DP of cellulose and the loss of paper folding endurance (FE) using three model samples (pure cellulose, groundwood pulp paper, and degraded groundwood pulp paper) at accelerated ageing were investigated. The existence of such correlations between DP and FE is supported by experimental results; the correlations are linear for pure cellulose and groundwood pulp paper ageing, while exponential correlation was observed in case of degraded groundwood pulp paper. The results indicate that the rate of paper degradation can be evaluated by means of the rate of glycosidic bonds breaking in cellulosic polymer chains both for cellulose and groundwood pulp paper.

We propose a simple and low-cost flow-through electrode for electrochemical cells used for instance in capacitive desalination. We have coated macro-porous carbon fiber papers with various loads of carbon microporous particles to combine both a high surface area and an open structure for good fluid dynamics. In this first study, we restrict our investigation to the charging/discharging behavior, the identification of side reactions, and the effect of geometry on the diffusion of ions. The electrochemical performance was first investigated by cyclic voltammetry and galvanic charge–discharge techniques. The specific capacitance increases by three orders of magnitude upon adding the carbon particles. Then, electrochemical impedance spectroscopy revealed the presence of charge transfer phenomena and modification in the mass transport by the diffusion process for the coated electrode. Graphical abstract SEM image of the surface morphology of the cross section of CP/CFP/CP structure of the flow-through electrode.

The influence of surface-applied original and enzymatically-modified sugar beet pectin on strength properties of fluting, coating base paper, and core board was investigated. The effect was compared with the application of commercial strength-increasing agents. With increasing the polymer uptake, measured strength of paper increased. Original sugar beet pectin increased the strength properties of papers, at the same uptake of polymer, to a higher extent than oxidised potato starch or modified grain flour, while the effect of enzymatically-modified sugar beet pectin was the lowest. For the same increase of paper strength, a several times higher uptake of enzymatically-modified sugar beet pectin was required when compared with the original pectin, oxidised potato starch, or modified grain flour.

The interest in using magnetic nanoparticle (MNPs) as a carrier for immobilization is overwhelming due to high surface area and lightweight properties. However, the conventional synthesis of MNPs required use of high amount of chemicals and is a time-consuming process. Thus, in the present research, magnetized multiwall carbon nanotubes (m-MWCNTs) were successfully synthesized via water-based system using simple steps. The synthesized m-MWCNTs was used as carrier for the immobilization of cellulase. Cellulase was proven to be successfully bounded on m-MWCNTs using Fourier transform infrared spectroscopy that revealed a peak at 580.33 cm−1 indicating Fe–O stretching in parallel with observation of rougher and coarser surface of m-MWCNTs through scanning electron microscope. The total binding efficiency of cellulase to the m-MWCNTs was determined to be 95% at 5 mg/mL of the enzyme concentration. The activity of the immobilized cellulase was evaluated using carboxymethyl cellulose (CMC) as a substrate. Both of free and immobilized cellulase showed optimum working condition at 50 °C and pH 5. Furthermore, the immobilized cellulase was found to be able to retain more than 50% of its initial activity at the fifth cycle of the hydrolysis of CMC and filter paper. A similar activity was recorded with paddy straw at the third cycle of hydrolysis.

Organic acids, e.g, citric acid, fumaric acid, lactic acid, malic acid, pyruvic acid and succinic acid, have important role in the food industry and are potential raw materials for the sustainable chemical industry. Their fermentative production based on renewable raw materials requires innovatively designed downstream processing to maintain low environmental impact and resource efficiency throughout the production process. The application of bipolar membranes offers clean and effective way to generate hydrogen ions required for free acid production from its salt. The water dissociation reaction inside the bipolar membrane triggered by electric field plays key role in providing hydrogen ion for the replacement of the cations in organic acid salts. Combined with monopolar ion-exchange membranes in a bipolar membrane electrodialysis process, material flow can be separated beside the product stream into additional reusable streams, thus minimizing the waste generation. This paper focuses on bipolar membrane electrodialysis applied for organic acid recovery from fermentation broth.

Graphical abstract Hydroxychloroquine (HCQ) and favipiravir (FPV) are known to be effective antivirals, and there are reports about their use to fight the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) despite that these are not conclusive. The use of combined drugs is common in drug discovery, and thus, we investigated HCQ and FPV as a combined drug. The density functional theory method was used for the optimization of geometries, spectroscopic analysis and calculation of reactivity parameters. The quantum theory of atoms in molecules was applied to explain the nature of the hydrogen bonds and confirm the higher stability of the combined drug. We also evaluated the absorption, distribution, metabolism and excretion (ADME) parameters to assess their drug actions jointly using SwissADME. The preliminary findings of our theoretical study are promising for further investigations of more potent and selective antiviral drugs. Supplementary Information The online version contains supplementary material available at 10.1007/s11696-021-01946-8.

The present paper concerns the partial updraft gasification of wheat–rye straw pellets, using air as a gasification agent. The aim of this paper is to examine the impact of biochar and ash outflow during the updraft gasification process on the parameters of the latter. For this purpose, a series of five experiments with different parameters of biochar and ash outflow and a reference experiment were carried out with a constant amount of supplied air. The results of the research show that higher volumetric outflows of biochar and ash increase the calorific value (from 6.7 to 7.4 MJ/Nm3) and production (from 34.8 to 40.3 Nm3/h) of the producer gas, as well as the rate of fuel feed rate (from 30 to 43 kg/h). Reductions in the yield of gas (from 1.16 to 0.94 Nm3/kgfuel), equivalence ratio (from 0.125 to 0.087), and cold gas efficiency (from 44.7 to 40.2%) were observed. The content of gravimetric tar in producer gas was typical of updraft gasification and fluctuated within a range of 65‒125 g/Nm3.

Pine needles are the by-product from the pine forest and cause of wild forest fire. A batch type portable charring drum was evaluated for converting pine needles to char and product gas with an aim to produce good quality char on-site. Char and product gas were characterized for their suitability as biochar and compared with chars derived from electrically heated batch type tubular reactor. The maximum conversion efficiency was found to be 29.3% at 80% loading, 50 m3 h−1 air flow rate and 90-min gasification time. Elemental analysis showed the maximum carbon content of 76.5% in the derived char which was comparable to the char derived at 400 °C. Other chemical properties also resembled the char produced at 400 °C. For good quality char which can qualify as biochar as per the guideline of European Biochar Certificate, gasification time is needed to continue up to 120 min at 60% loading.

There is an urgent need for reliable cure and preventive measures in this hour of the outbreak of SARS-CoV-2. Siddha- and Ayurvedic-based classical formulations have antiviral properties and great potential therapeutic choice in this pandemic situation. In the current study, in silico-based analysis for the binding potential of phytoconstituents from the classical formulations suggested by the Ministry of Ayush (Kabasura Kudineer, Shwas Kuthar Rasa with Kantakari and pippali churna, Talisadi churna) to the interface domain of the SARS-CoV-2 receptor-binding domain and angiotensin-converting enzyme 2 was performed. Maestro software from Schrodinger and tools like Glide Docking, induced fit docking, MM-GBSA, molecular dynamics (MD) simulation, and thermal MM-GBSA was used to analyze the binding of protein PDB ID:6VW1 and the selected 133 ligands in comparison with drug molecules like favipiravir and ribavirin. QikProp-based ADMET evaluation of all the phytoconstituents found them nontoxic and with drug-like properties. Selection of top ten ligands was made based on docking score for further MM-GBSA analysis. After performing IFD of top five molecules iso-chlorogenic acid, taxiphyllin, vasicine, catechin and caffeic acid, MD simulation and thermal MM-GBSA were done. Iso-chlorogenic acid had formed more stable interaction with key residue among all phytoconstituents. Computational-based study has highlighted the potential of the many constituents of traditional medicine to interact with the SARS-CoV-2 RBD and ACE2, which might stop the viral entry into the cell. However, in vivo experiments and clinical trials are necessary for supporting this claim. Supplementary Information The online version contains supplementary material available at 10.1007/s11696-021-01917-z.

The ongoing pandemic caused by the severe acute respiratory syndrome 2 (SARS-CoV 2) has led to more than 168 million confirmed cases with 3.5 million deaths as at 28th May, 2021 across 218 countries. The virus has a cysteine protease called main protease (Mpro) which is significant to it life cycle, tagged as a suitable target for novel antivirals. In this computer-assisted study, we designed 100 novel molecules through an artificial neural network-driven platform called LigDream (https://playmolecule.org/LigDream/) using 3-O-(6-galloylglucoside) as parent molecule for design. Druglikeness screening of the molecules through five (5) different rules was carried out, followed by a virtual screening of those molecules without a single violation of the druglike rules using AutoDock Vina against Mpro. The in silico pharmacokinetic features were predicted and finally, quantum mechanics/molecular mechanics (QM/MM) study was carried out using Molecular Orbital Package 2016 (MOPAC2016) on the overall hit compound with controls to determine the stability and reactivity of the lead molecule. The findings showed that eight (8) novel molecules violated none of the druglikeness rules of which three (3) novel molecules (C33, C35 and C54) showed the utmost binding affinity of −8.3 kcal/mol against Mpro; C33 showed a good in silico pharmacokinetic features with acceptable level of stability and reactively better than our controls based on the quantum chemical descriptors analysis. However, there is an urgent need to carry out more research on these novel molecules for the fight against the disease. Supplementary Information The online version contains supplementary material available at 10.1007/s11696-021-01899-y.

The present study introduces an active macroscopic mixing device for aqueous sanitizer preparation. It operates on a piezoelectrically actuated oscillating cantilever beam appropriate for disparate feature liquid–liquid mixing. A piezoelectric actuated cantilever beam at the third bending mode vibration frequency produces extreme vibrations when excited by a suitable voltage. Potent mixing occurs as the robust vibration energy is sent from the beam to the container’s test liquid. In this work, different glycerol concentrations were mixed with deionized (DI) water and ethanol at 25 ℃. The mixer’s performance to mix DI water–glycerol, ethanol–glycerol, and DI water–ethanol–glycerol considered a sanitizer was tested. The sanitizer mixture’s measured density, viscosity, and surface tension values were 0.7502 g cm−3, 1.8906 cp, 34.7893 dyne cm−1, respectively. The measured aqueous-based glycerol mixture’s density and viscosity values were validated with the computed values by previous researcher’s models and formulas. The observed density reading of the aqueous-based 25% glycerol concentration mixture agreed with the estimated value of a density model having ± 1.1290% deviation. Supplementary Information The online version contains supplementary material available at 10.1007/s11696-021-01886-3.

Given the characteristics of the high content of phenols and poor biodegradability in lignite upgrading wastewater, the Fenton oxidation process was used as a pretreatment technology of the biochemical treatment process. Therefore, the best reaction conditions within the range of test conditions were investigated. The results show that the best reaction conditions of the Fenton oxidation system within the range tested are as follows: The ratio of H2O2/chemical oxygen demand (COD) was 1.25, the pH value was 3.5, the H2O2/Fe2 + molar ratio was 1:1, and the reaction time was 60 min. Under these conditions, the highest biochemical oxygen demand (BOD5)/COD value obtained was 0.74; the COD removal efficiency increased by 63.55%. And the output of iron sludge characterized by 30-min static sedimentation ratio was about 45.1%.

The removal of nitrogen and phosphorus from wastewater developed with established struvite (magnesium ammonium phosphate; MAP) production technology is the best alternative to newly produced or freshly degraded phosphate fertilizers. However, the production of struvite from domestic wastewater is not used extensively as initially expected in India because of the poor quality of production technology, competitive prices, and consumer acceptance as a fertilizer. Against this background, the present study aims to expand struvite production from phosphorus-rich wastewater, and bittern waste materials as a secondary source of magnesium in an inverse fluidized bed reactor by investigating their hydrodynamics characteristics. The study examined the influence of hydrodynamic parameters such as minimum fluidization velocity, bed expansion and pressure drop with polypropylene beads of different density under an optimized Mg/P ratio of 1.0. The O-phosphate recovery efficiency of over 95% was achieved by reaching the minimum fluidization velocity at a bed height of 45 cm, with a polypropylene bead with a diameter of 5 mm and a density of 836 kg/m3. The yield of struvite in a day for ten cycles for 30 days was estimated to be about 30–35 kg with 92% phase purity (XRD pattern of crystal). The cost economics suggested that the full-scale IFBR operation for struvite crystallization would be helpful for the community wastewater treatment plant.

Graphic abstract Detailed concentration-dependent measurements of sound absorption and velocity have been performed in dexamethasone sodium phosphate (DSP) aqueous solutions in the MHz frequency range. A single well-resolved relaxation process dominates the experimental acoustic spectra following a Debye-type distribution function. The analysis of the temperature-dependent ultrasonic relaxation data also revealed analogous effect with concentration on the relaxation spectra. All acoustic parameters were estimated by means of a fitting procedure. The behavior of the relaxation frequency and amplitude with concentration allowed us to assign the observed process to self-association mechanism. Combining the ultrasonic and electric conductivity data, the self-association scheme has been established. The thermodynamic constants and the rate of the aggregation due to hydrophobic interactions have been estimated in view of the Eyring’s theory. The concentration dependence of relaxation amplitude and characteristic frequency revealed that the presence of additional relaxation processes in the spectra related to additional mechanisms, such as conformational changes and proton-transfer reaction is excluded and the self-association process considered here was found to dominate in this frequency range. The results have been discussed in view of the fair ability of DSP for hydrophobic interactions and aggregate formation in aqueous environment.

This study aimed to examine the differences between the antioxidant capacity, and the total polyphenol content of the seed of eight different grape varieties. We also attempt to create a functional loaf enriched with grape seed meal. To achieve this goal, 3, 6, and 9% of the grape seed meal were added to the loaves made of bread flour and gluten-free flour mixture, and then the changes in their antioxidant and polyphenol content were examined. Based on the results, there were significant differences between the polyphenol and antioxidant content of grape seed varieties. The antioxidant content of the grape seeds varied between 228.50 mg AAE/g (94.80 mg TE/g) and 438.33 mg AAE/g (181.86 mg TE/g) in case of fatty samples, and between 176.29 mg AAE/g (41.24 mg TE/g) and 424.91 mg AAE/g (99.40 mg TE/g) in case of defatted samples. The total polyphenol content of the fatty samples changed between 91.16 and 221.81 mg GAE/g; in case of defatted samples, it ranged from 46.01 to 207.68 mg GAE/g. Rhine Riesling contained the greatest amount of these compounds. The functionality of loafs was confirmed by spectrophotometric analysis. Total polyphenol content ranged from 0.91 to 3.16 mg GAE/g in case of wheat loafs, and from 1.39 to 5.92 mg GAE/g in case of gluten-free loafs, while the total antioxidant content changed between 0.70 and 6.44 mg AAE/g in case of wheat loafs, and ranged from 2.55 to 9.75 in case of gluten-free loafs. Graphic abstract

The sugarcane bagasse (SCB) can be utilized to obtain various value-added products like levulinic acid, glucose, xylose, ethanol, etc. with suitable pretreatment and subsequent extraction and isolation processes. There are several ways to pretreat SCB and one among them is by using ionic liquids (ILs). The ILs are non-volatile and versatile solvents used mainly due to their efficiency in promoting cell disruption and by altering cellulose crystallinity, thereby making the SCB more accessible to the enzymes. The pretreatment is followed by enzymatic hydrolysis and fermentation to obtain a variety of products. The first objective of this minireview is to put forward an up-to-date survey of pretreating renewable SCB using non-volatile ILs to form value-added products, thus helping in selection of the best IL for this purpose. The second objective is to understand various ways to open doors for use of ILs in biorefineries by reducing cost of IL, by recycling and reusing the ILs or by reducing loading amounts of ILs. A link between ILs and solid wastes recovery as well as their reuse is presented in a circular bioeconomy aspect. In future, biorefineries may use ILs in the processing of lignocellulose.

The quantitative analysis of andrographolides in Andrographis paniculata plant materials is essential for pharmaceutical factories. This analysis cannot be done for all samples due to the conventional process using the extraction and HPLC methods requires a long analysis time and sample destruction. Therefore, near-infrared spectroscopy (NIRS) was employed to classify the class of A. paniculata and to determine the content of two active ingredients, andrographolide (AP1) and dehydroandrographolide (AP3) in A. paniculata, rapidly and non-destructively. One hundred twenty dried powder samples were obtained from aerial parts, branches, leaves, and branches mixed with leaves. The NIR absorption scans were collected from a broad spectral region (1000–2500 nm). Then, the scanned samples were extracted and analyzed for their AP1 and AP3 contents using an HPLC reference method. The success classification model based on AP1 level was developed using the second derivative pretreated NIR spectra of the entire wavelength region using the Partial Least Squares-Discriminant Analysis (PLS-DA) method. The NIR calibration models were developed and tested for quantitative analysis with 50 independent samples. The models were identified for the analysis of the AP1 content with excellent performance (correlation coefficient (R) = 0.98; standard error of validation (SEV) = 0.24%) and for the analysis of the AP3 content at a good level of efficiency (R = 0.93; SEV = 0.15%). This study showed that NIR spectroscopic method offers rapid analysis for the selection of A. paniculata that meets the requirement in bioactive amount. Graphic Abstract Supplementary Information The online version contains supplementary material available at 10.1007/s11696-021-01746-0.

In the present investigation, dye, chemical oxygen demand (COD), turbidity removal, and dissolved oxygen (DO) increment were carried out using raw wheat bran as an adsorbent which was coated on the low-density polypropylene (PP) in the inverse fluidization. The obtained coated raw wheat bran on PP was tested as an adsorbent in this research work. Prepared raw wheat bran was characterized by FTIR, SEM, and EDS. The obtained raw wheat bran has 58.53% carbon content. The prepared adsorbent was used to remove different pollutants from the prepared synthetic textile azo dye. Experiments have been conducted in batch adsorption processes with different parameters such as initial dye concentration, pH, airflow timing, and the adsorbent dose on removal effectiveness of dye, COD, turbidity removal, and DO enhancement. The central composite design (CCD) technique of response surface methodology (RSM) and different known isotherms models were applied to the batch experimental data for removal of an azo dye, COD, turbidity, and DO enhancement.

Due to the low efficiency of physical–chemical treatments, advanced oxidative processes (AOP) appear as an efficient treatment alternative for removing organic compounds. To replace some of the reagents used in the photo-Fenton AOP with low-cost materials, the present study evaluated the degradation of direct black dye 22 (DB22) under LED radiation in a homogeneous and heterogeneous medium (iron residue). The best treatments operational conditions were determined and kinetic study was carried out. Then, artificial neural networks (ANN) were used to predict the processes' degradation behavior. In addition, toxicity tests were performed with seeds and bacteria. The homogeneous treatment reached DB22 total degradation after 120 min (2 mg L−1 of Fe, pH between 3–4 and 80 mg L−1 of H2O2) and the same result was obtained for the heterogeneous process after 480 min (0.5 g L−1 of RFe, granulometric range of 0.97). Furthermore, the toxicity tests indicated that the homogeneous process was the least aggressive to the species of seeds and the bacterial strains. The obtained results also allowed an efficient prediction of degradation through ANN application for both processes. Finally, the study showed that the application of heterogeneous photo-Fenton AOP using LED radiation and iron residue as the catalyst proved to be a cheap and effective alternative in the degradation of the dye, which indicates the possibility of its application on a large scale, improving the quality of the effluents released by the textile industry, without excessively increasing the cost of the process.

Processing of lignocellulosic biomass includes four major unit operations: pre-treatment, hydrolysis, fermentation and product purification prior to biofuel generation via anaerobic digestion. The microorganisms involved in the fermentation metabolize only simple molecules, i.e., monosugars which can be obtained by carrying out the degradation of complex polymers, the main component of lignocellulosic biomass. The object of this paper was to evaluate the saccharification conditions and identify the process parameters that should be applied to improve the saccharification efficiency of lignocellulosic biomass, defined as the simple sugars concentration, which was considered as a crucial parameter for hydrogen generation via dark fermentation. Drawing global conclusions about the occurring changes in the biomass requires learning about the nature of the biomass structure and composition at different stages of the process. Therefore, techniques for analysis, as FTIR, HPLC and SEM were applied. The experiment was planned employing Box–Behnken design. The advantageous operating conditions and the composition of saccharification enzymatic cocktail were identified and their values occurred similar in the applied border conditions for all tested biomass types. Analysis of the intermediate solid and liquid streams generated during the pre-treatment procedure revealed several structural and compositional changes in the biomass.

Elevated iron content in low-grade kaolin is one of the chemical factors detrimental for its industrial applications. Therefore, various physical and chemical methods have been applied to decrease iron concentration in kaolin. One of the more feasible and environmentally friendly method is biobenefication via microbially-induced bioextraction. Therefore, this paper provides data on fungal bioextraction of iron from kaolin sample when incubated with fungal Aspergillus niger strain. After 19-day cultivation, approximately 45% of iron impurities have been bioextracted by fungus and distributed into fungal biomass or culture medium. The bioextraction was triggered by both acidification of culture medium by fungus (below pH of 1.5) and organic acids production, which are biologically conversed from glucose. However, bioextraction of silicon and aluminium, which form building blocks of clay minerals in kaolin, was reasonably low and did not overcome 0.15%. Thus, our data indicate that the bioextraction of iron using A. niger strain for kaolin processing is a viable alternative method for increasing quality of the low-grade kaolin.

This paper reports the use of design of experiments (DOE) with the objective of finding optimal industrial conditions for fat bleaching in soaps production. Laboratory experiments were performed evaluating the effects of residence time, temperature and pressure on the resulting fat color by two different colors scales: red (R) and yellow (Y), through light emitted or reflected by the mixture. Statistical analysis as well as a visual analysis of response surfaces indicated that only factors “Time”, “Temperature”, “Pressure” and “Time × Temperature” presented considerable effects on the total color, and an operation with long residence time, low pressures and low temperatures would be ideal for removal of the R and Y colors in an easy and effective manner. The responses found in these experiments were reproduced in industrial equipment, and the fat color results obtained were within the indicated experimental value. This approach is of simple laboratory execution, good reproducibility at the industrial level and also with good fat bleaching efficiency. Our finds indicated that 50 min of residence time, 70 °C and 6.7 kPa would be ideal operation conditions in industrial scale.

The increase in glycerol in the global market (from increased biodiesel production) has led to a glut. Of the different methods of utilising crude glycerol, steam reforming has been explored as a viable energy generation technique. Over the years, research has explored process optimisation, process catalysis, thermodynamics analysis, kinetic modelling, exergy and energy analyses, techno-economic analyses, environmental performance, and computational fluid dynamics (CFD) simulations in this regard. This paper reviewed and catalogued the current state of knowledge on the production of bio-hydrogen by the steam reforming of glycerol obtained from transesterification while revealing key knowledge gaps. It was observed that impurities in crude glycerol have much more negative effect on the overall yield than on the product selectivity. Impurities such as water and methanol favour the production hydrogen. The catalysts for steam reforming are usually noble and transition metals co-precipitated together or impregnated on metal oxides and ores. Nickel is considered as the best catalyst for the process with temperature and pressure optimal pegged around 650–900 °C and 1 atm. Gaping gaps in knowledge abound in the research area and these are in the domain of crude glycerol use, fluidised bed use, artificial sorbent use, pilot scale studies, cost and profitability analysis, and investigations on carbon deposition behaviour.

The contamination of water resources due to the presence of persistent organic pollutants, such as dyes, is a cause for concern, since these substances are resistant to conventional treatments adopted in wastewater treatment plants. In this context, the present work evaluated the degradation of the dye AV17, used in sanitizing industries, through different advanced oxidation processes (AOP). AOP of photoperoxidation, Fenton and photo-Fenton were employed. It was found that the photoperoxidation/UV-C system was more efficient in the treatment of the dye, reaching degradations of 68.27%, 88.16% and 99.35% for the characteristic wavelengths of 254, 307, 548 nm, respectively. The Fenton process and the photo-Fenton/solar system, especially with natural solar irradiation, only managed to promote the discoloration of the solution by degrading the chromophore group. The kinetic study indicated a better adjustment of the experimental data to the pseudo-first order model, with R2 > 0.94 for the mentioned AOP. The modeling by ANN allowed to predict the degradation of AV17 through an MLP 5-6-3 BFGS 297 type network, with R2 values higher than 0.9864 for training, testing and validation. Toxicity tests with Lactuca sativa seeds showed that the treatment via photoperoxidation/UV-C and photo-Fenton/solar led to a reduction in the toxicity of the solution contaminated by the dye. However, for the solution treated by Fenton process, toxicity was observed.

A number of treatments to municipal wastewater include advanced oxidation processes such as solar photo Fenton and solar photo-catalytic, biological treatment and the use of specific technologies when wastewater is polluted with heavy metals. Therein, the use of membranes, sorption processes with natural adsorbents and/or composites, and biosorption have proved to remove heavy metals efficiently. This investigation aimed to describe the behavior of the thiourea-modified natural clinoptilolite to remove cadmium from wastewater only filtered and wastewater with biological oxidation, in a column system, considering the properties of ion exchange and adsorption of the modified zeolitic material involving the novelty of this work. The importance of counting on feasible technologies to dispose of water is, without a doubt, a priority, particularly in areas, where average rainfall barely reaches 45 mm. Wastewater was treated in a continuous system with a thiourea-modified clinoptilolite-rich tuff. The initial concentration of cadmium in the wastewater was 2.4 mg/L, and an additional amount was added to reach a level of 31 mg/L. The breakthrough curves were obtained, and a mass balance was applied to the results, which accounted for the constant of adsorption 0.345 m3/kg, with a determination coefficient of 0.754. Finally, the capacity of the column system was evaluated for wastewater with biological oxidation. The results showed a cadmium uptake of 34.17%, which led to suggest a treatment in a two-column series.

We developed an environmental recycling process for textile dyeing sludge that involved a magnetizing roasting–magnetic separation process followed by the preparation of a ceramic filter. The optimal parameters for the magnetizing roasting process included blending the textile dyeing sludge with 5.0% content of coal and roasting at 800 °C for 45 min. The main iron-bearing mineral (Fe2O3) was converted to Fe3O4. The roasted ore was beneficiated by low-intensity magnetic separation (0.15 T strength of the magnetic field). A concentrate with 57.85% iron grade and 68.11% iron recovery was obtained. A ceramic filter material produced from the tailings of the magnetic separation process met the national standard requirements for water treatment applications. These results offered an effective approach to solve an environmental problem associated with textile dyeing sludge waste products.

Bitter melon is a source of bioactive compounds, such as phenolic compounds and is widely used as medicinal and food plant. This study aimed at evaluating the distribution of phenolic compounds in the different parts (pulp, peel and seeds) of ripe bitter melon fruit (Momordica charantia) and in the whole unripe fruit through its quantification by UPLC–MS/MS using a proposed ultrasonic-assisted extraction method. Altogether, 18 phenolic compounds were determined in samples from bitter melon. The pulp of the ripe fruit and the whole unripe fruit showed the highest amounts of total phenolic compounds, 964.00 ± 15.64 and 918.63 ± 18.22 mg g−1, respectively. It was possible to identify naringenin, chrysin, luteolin and apigenin in unripe fruit, and chrysin and apigenin in all parts of the ripe fruit. These phenolic compounds had not been previously reported in other studies for bitter melon. Thus, the pulp can be considered as a promising source of phenolic compounds, deserving attention in future studies.

Prevention of struvite formation at wastewater treatment plants (WWTPs) is currently possible using several approaches. However, failure of these measures and subsequent spontaneous struvite formation may lead to serious operational problems. A similar problem occurred at a municipal WWTP with enhanced phosphorus removal and anaerobic sludge digestion, where spontaneous struvite precipitation caused clogging of the pipes with digested sludge. For direct struvite dissolution in the sludge pipes, organic and inorganic acidic solutions were investigated. It was shown that using solutions of pH