Sustain. Chem., Volume 4, Issue 1 (March 2023) – 9 articles

The current study examines the feasibility of recycling artificially polluted wastewater that contains crystal violet (CV) organic dye by using Azadirachta indica sawdust (AISD) waste as a highly cost-effective adsorbent. Different analytical techniques, viz., SEM/EDX, TEM/SAED, BET, XRD, TGA-DTG, point of zero charge (pH_pzc), and FTIR, were used to characterize the adsorbent. Studies of batch adsorption were performed with varying contact times, starting concentrations of CV, pH levels, doses and particle sizes of AISD, and temperatures. After assessing the results using the Langmuir, Freundlich, and Temkin isotherm models, it was observed that the Langmuir model best fits the data. Various models were employed to analyze the kinetic findings, and it was confirmed that the pseudo-second-order model appears to be the most accurate. The values of ΔH° (50.01 kJ mol⁻¹), ΔG° (−10.254 to −5.043 kJ mol⁻¹), and ΔS° (182.47 J K⁻¹mol⁻¹), obtained in a temperature range of 303–333 K, revealed that the process was spontaneous, endothermic, and accompanied by an increase in entropy. Based on experimental findings and their analyses, it was concluded that the adsorbent made from AISD is one of the most effective among those obtained from domestic, agricultural, and industrial wastes. Thus, the present adsorbent can be effectively exploited to make dye-contaminated water reusable. Full article

This work deals with the development of non-isocyanate polyurethane (NIPU) composites with an aniline oligomer, viz., tetraniline (TANI) for corrosion-resistant coatings. Firstly, epoxidizedsoyabean oil was converted to carbonated oil by inserting CO₂ under high temperature and pressure into the epoxy ring. Then, varying weights of oligoaniline—0.5, 1, 2 and 4 wt % (based on the weight of CSBO)—were added to CSBO and cured with tetraethylenepentamine (TEPA, 25 wt % based on CSBO) at 80 °C for 12–15 h. The effects of oligomer loading on the thermal, mechanical and surface wetting properties of the free standing films were studied. The ATR-FTIR spectra of the films exhibited peaks corresponding to the bis-carbamate linkages, confirming the formation of urethane linkages. TGA analysis showed that the addition of oligoaniline did not alter the initial degradation temperature much; however, the residue increased with increasing loading of tetraniline. Both tensile strength and elongation (at break) increased with increasing oligoaniline content. While the glass transition temperature of the films was observed at approximately room temperature, i.e., 20–30 °C, for all the compositions, the contact angles of the composites were found to be less than that of the bare NIPU films. However, all the compositions were hydrophobic, exhibiting contact angles in the 98–110° range. SEM analysis of the cross-sections of the films confirmed the uniform distribution of tetraniline particles and surface morphology showed that the roughness increased with the loading of tetraniline from 0.5 to 4%. MS panels coated with NIPU exhibited good barrier properties and as loading of TANI increased, the rate of corrosion decreased. Salt spray tests indicated that oligoaniline improved the adhesion of the coating to MS and corrosion resistance compared to the neat NIPU coating. Full article

Owing to the unique property of large surface area/volume of nanoparticles, scientific developments have revolutionized the fields of nanotechnology. Nanoparticles can be synthesized through physical, chemical, and biological routes, where biologically synthesized nanoparticles are also referred to as biogenic-synthesized nanoparticles or bionanoparticles. Bionanoparticles exploit the inherent reducing property of biological entities to develop cost-effective, non-toxic, time-efficient, sustainable, and stable nanosized particles. There is a wide array of biomedical focus on metallic nanoparticles, especially silver nanoparticles, due to their distinctive physiochemical properties making them a suitable therapeutic molecule carrier. This article aims to provide a broad insight into the various classes of living organisms that can be exploited for the development of silver nanoparticles, and elaboratively review the interdisciplinary biomedical applications of biogenically synthesized silver nanoparticles in health and life sciences domains. Full article

Solvent-free mechanochemical reactions represent an important path towards sustainable chemistry. The preparation of Prussian blue from solid iron and hexacyanoferrate compounds by the simple use of a mortar and pestle is an easy, inexpensive, and fast method to teach mechanochemical reactions. The course of the reaction can be followed very well visually via the color change of the solid mixture towards blue. With this communication, earlier publications on Prussian blue and mechanochemistry in the field of chemical education are updated and extended. Full article

Bioactive compounds like piperine (alkaloids) offer a variety of health benefits due to their biological and pharmacological potential. Piperine has been revealed to have anti-inflammatory, anti-aging, anti-diabetes, anti-bacterial, anti-ulcer, and anti-carcinogenic characteristics. Recent research has been conducted to extract piperine using effective and environmentally friendly techniques. In this study, we sought to assess the potential and efficacy of natural deep eutectic solvents to extract piperine from black pepper seeds using an ultrasound-assisted extraction technique. A Box–Behnken design combined with response surface methodology was used to evaluate the optimum extraction conditions of piperine. Extraction efficiency was evaluated based on the extraction yields of piperine, antioxidant activity, total polyphenols, and total flavonoids. The results showed that the choline chloride-citric acid-1,2-propylene glycol combination (1:2:2 molar ratio) with 25% (v/v) of water was the most effective at extracting piperine from black pepper. It was found that the extraction yield of piperine was significantly influenced by the liquid–solid ratio and extraction time. The optimal extraction conditions were determined and it was found that antioxidant activities and total polyphenol content in the piperine-rich extracts were remarkably related to the piperine content. The piperine extract purity was found to be 90%. Our results indicate that black pepper could be used as a functional food application. Full article

The fabrication of metal oxide nanofibers using (titanium (IV) isopropoxide) and (tin (IV) tert-butoxide) of weight ratio 1:1 precursor in presence of poly (vinyl pyrrolidone) as a binder using a well-known electrospinning technique is reported. The average diameter of TiO₂, SnO₂, and composite TiO₂-SnO₂ nanofibers were found to be in the range 75–110 nm. The nanofibers were characterized using thermogravimetric analysis (TGA) to understand the polymer evaporation temperature and further analyzed using scanning electron microscopy (SEM) to study the morphology of the nanofibers. The oxidation states of titanium (Ti) and tin (Sn) ions were analyzed using X-ray photoelectron spectroscopy (XPS), indicating that the TiO₂ undergoes a change even after loading SnO₂. The photocatalytic efficiency of the composite TiO₂-SnO₂ fibers was investigated to study the degradation capabilities under ultraviolet (UV) light towards industrial polluting dyes such as Alcian Blue, Alizarin Red S, Bilirubin, Brilliant Blue, Bromophenol Blue, and Rhodamine B ITC. Rhodamine B showed a significant degradation rate of about 0.0064 min⁻¹ in comparison to the other dyes. Full article

In this work, a greener approach for the extraction of Greek propolis using ultrasound-assisted extraction method in combination with Natural Deep Eutectic Solvents (NADES) is presented. Propolis is a natural material of outmost interest as it possesses various biological and pharmacological activities and is therefore used for the manufacturing of extracts useful to various fields, such as pharmaceutics, cosmetics etc. Herein, five NADES were task-specifically selected as appropriate extraction solvents since they provide important assets to the final NADES-extracts, comparing to the conventionally used organic solvents. The screening study of the prepared solvents indicated the NADES L-proline/D,L-Lactic acid as the most effective medium for the raw propolis extraction due to the extract’s high total phenolic content as well as its’ significantly higher antioxidant activity. Then, the extraction using the selected NADES, was optimized by performing Experimental Design to study the effect of extraction time, propolis-to-solvent ratio and the %NADES content in the NADES-water system. All the extracts were characterized regarding their antioxidant activity and total phenolic content. The optimum NADES-extract as well as an extract derived by extraction using a conventional hydroethanolic solution were further characterized by performing LC/MS/MS analysis. The results showed that the NADES-extracts composition was similar or superior to the hydroethanolic extracts regarding the presence of valuable phytochemicals such as apigenin, naringenin etc. A disadvantage that is usually mentioned in the literature regarding the extractions using NADES is that the extracted bioactive compounds cannot be easily separated from the NADES in order to obtain dry extracts. However, this drawback can be converted to an asset as the task-specifically designed NADES that are used in this study add value to the end product and the optimum as-obtained NADES-extract has been successfully incorporated in a cosmetic cream formulation. In this work, The antioxidant activity and organoleptic characteristics of the cream formulation were also determined. Full article

Shellac and aleuritic acid manufacturing industries generate a lot of alkaline aqueous effluent during the process of manufacture of shellac and aleuritic acid from the seedlac/sticklac. The generated effluent contains lac resin, lac wax, lac dye and other water-soluble organic acids. Shellac industries in India face problems with the disposal of aqueous effluent due to the presence of considerable amounts of natural organic molecules and the dark colour solution. To address these problems, we have developed a novel method for the selective recovery of the lac resin from the alkaline aqueous effluent of shellac manufacturing industry. The recovered lac resin has been characterized by ¹³C-NMR, FT-IR and melting point and the data were compared with standard industrial-grade resin. The recovered lac resin was evaluated by the lac manufacturing industry for commercial applications. Full article