Production of magnetic chitinous microcages from ephippia of zooplankton Daphnia longispina and heavy metal removal studies

Solving urban water microplastics with bacterial cellulose hydrogels: Leveraging predictive computational models

The prevalence of microplastics (MPs) in both urban and aquatic ecosystems is concerning, with wastewater treatment plants being considered one of the major sources of the issue. As the focus on developing sustainable solutions increases, unused remnants from bacterial cellulose (BC) membranes were ground to form BC hydrogels as potential bioflocculants of MPs. The influence of operational parameters such as BC:MPs ratio, hydrogel grinding, immersion and mixing time, temperature, pH, ionic strength, and metal cations on MPs flocculation and dispersion were evaluated. A response surface methodology based on experimental data sets was computed to understand how these parameters influence the flocculation process. Further, both the BC hydrogel and the hetero-aggregation of MPs were characterised by UV-Vis, ATR-FTIR, IGC, water uptake assays, fluorescence, and scanning electron microscopy. These highlights that the BC hydrogel would be fully effective at hetero-aggregating MPs in naturally-occurring concentrations, thereby not constituting a limiting performance factor for MPs' optimal flocculation and aggregation. Even considering exceptionally high concentrations of MPs (2 g/L) that far exceed naturally-occurring concentrations, the BC hydrogel was shown to have elevated MPs flocculation activity (reaching 88.6%: 1.77 g/L). The computation of bioflocculation activity showed high reliability in predicting flocculation performance, unveiling that the BC:MPs ratio and grinding times were the most critical variables modulating flocculation rates. Also, short exposure times (5 min) were sufficient to drive robust particle aggregation. The microporous nature of the hydrogel revealed by electron microscopy is the likely driver of strong MPs bioflocculant activity, far outperforming dispersive commercial bioflocculants like xanthan gum and alginate. This pilot study provides convincing evidence that even BC remainings can be used to produce highly potent and circular bioflocculators of MPs, with prospective application in the wastewater treatment industry.

Synthesis of novel adsorbent by incorporation of plant extracts in amino-functionalized silica-coated magnetic nanomaterial for the removal of Zn2+and Cu2+from aqueous solution

Magnetic nanoparticles owing to their superparamagnetic behaviour and specific reactive sites are facilitated to regenerate and reuse. Our present study determines the cointegration of the plant extracts of Cynodon dactylon and Muraya koenigii with the magnetic nanoparticle coated with silica layer and surface engineered with a specific amine group. The cointegrated magnetic nano adsorbent is characterized for its analytical feature and batch studies are performed to remove zinc (Zn²⁺) copper (Cu²⁺) metal ions. Fourier transform infrared spectroscopy reveals the presence of functional entities such as NH₂, Si-O-Si, C=C. The size of the cointegrated nano adsorbent (12-30 nm) was confirmed by field emission scanning electron microscopy whereas, a high-resolution transmission electron microscope affirms the nanosize of the particle constituted around 20 nm. Energy dispersive x-ray analysis confirms the presence of elements like Fe, N, Si and was confirmed by X-ray diffraction analysis and vibrating sample magnetometer affirms the superparamagnetic nature with the high magnetic saturation value (M_s - 30 emug^-1). The cointegrated nano adsorbent reveals the maximum adsorption capacity of Zn²⁺ as 78.24 mg.g^-1 and Cu²⁺ as 81.76 mg.g^-1 of the adsorbent under the optimized conditions of contact time 45 min, pH 6.0 and temperature 35 °C. Kinetics such as pseudo-first-order, pseudo-second-order, Elovich, intraparticle diffusion and isotherm studies like Langmuir, Freundlich, Dubinin-Radushkevich and Temkin were performed to understand the mechanism of interaction between the nanoadsorbent and metal ions. The reaction system follows the pseudo-second-order kinetics and Langmuir isotherm model for both the Cu²⁺ and Zn²⁺ metal ions. To determine the reusing capacity of the cointegrated nanoadsorbent, the adsorption efficiency was studied for continuous twelve cycles with 80% recovery after subsequent acid treatment.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s40201-021-00696-9.

Antimicrobial Activity of Chemically and Biologically Treated Chitosan Prepared from Black Soldier Fly (Hermetia illucens) Pupal Shell Waste

Globally, the broad-spectrum antimicrobial activity of chitin and chitosan has been widely documented. However, very little research attention has focused on chitin and chitosan extracted from black soldier fly pupal exuviae, which are abundantly present as byproducts from insect-farming enterprises. This study presents the first comparative analysis of chemical and biological extraction of chitin and chitosan from BSF pupal exuviae. The antibacterial activity of chitosan was also evaluated. For chemical extraction, demineralization and deproteinization were carried out using 1 M hydrochloric acid at 100 °C for 2 h and 1 M NaOH for 4 h at 100 °C, respectively. Biological chitin extraction was carried out by protease-producing bacteria and lactic-acid-producing bacteria for protein and mineral removal, respectively. The extracted chitin was converted to chitosan via deacetylation using 40% NaOH for 8 h at 100 °C. Chitin characterization was done using FTIR spectroscopy, while the antimicrobial properties were determined using the disc diffusion method. Chemical and biological extraction gave a chitin yield of 10.18% and 11.85%, respectively. A maximum chitosan yield of 6.58% was achieved via chemical treatment. From the FTIR results, biological and chemical chitin showed characteristic chitin peaks at 1650 and 1550 cm⁻¹—wavenumbers corresponding to amide I stretching and amide II bending, respectively. There was significant growth inhibition for Escherichia coli, Bacillus subtilis,Pseudomonas aeruginosa,Staphylococcus aureus, and Candida albicans when subjected to 2.5 and 5% concentrations of chitosan. Our findings demonstrate that chitosan from BSF pupal exuviae could be a promising and novel therapeutic agent for drug development against resistant strains of bacteria.

A State-of-the-Art Review on Biowaste Derived Chitosan Biomaterials for Biosorption of Organic Dyes: Parameter Studies, Kinetics, Isotherms and Thermodynamics

Chitosan is a second-most abundant biopolymer on earth after cellulose. Its unique properties have recently received particular attention from researchers to be used as a potential biosorbent for the removal of organic dyes. However, pure chitosan has some limitations that exhibit lower biosorption capacity, surface area and thermal stability than chitosan composites. The reinforcement materials used for the synthesis of chitosan composites were carbon-based materials, metal oxides and other biopolymers. This paper reviews the effects of several factors such as pH, biosorbent dosage, initial dye concentration, contact time and temperature when utilizing chitosan-based materials as biosorbent for removing of organic dyes from contaminated water. The behaviour of the biosorption process for various chitosan composites was compared and analysed through the kinetic models, isotherm models and thermodynamic parameters. The findings revealed that pseudo-second-order (PSO) and Langmuir isotherm models were best suited for describing most of the biosorption processes or organic dyes. This indicated that monolayer chemisorption of organic dyes occurred on the surface of chitosan composites. Most of the biosorption processes were endothermic, feasible and spontaneous at the low temperature range between 288 K and 320 K. Therefore, chitosan composites were proven to be a promising biosorbent for the removal of organic dyes.