Effects of biochar and magnesium oxide on cadmium immobilized by microbially induced carbonate: Mobilization or immobilization in alkaline agricultural soils?

Microbially induced carbonate precipitation (MICP) is a promising technique for remediating heavy metal-contaminated soils. However, the effectiveness of MICP in immobilizing Cd in alkaline calcareous soils, especially when applied in agricultural soils, remains unclear. Biochar and magnesium oxide are two environmentally friendly passivating materials, and there are few reports on the combined application of MICP with passivating materials for remediating heavy metal-contaminated soils. Additionally, the number of treatments with MICP cement and the concentration of calcium chloride during the MICP process can both affect the effectiveness of heavy metal immobilization by MICP. Therefore, we conducted MICP and MICP-biochar-magnesium oxide treatments on agricultural soils collected from Baiyin, Gansu Province (pH = 8.62), and analyzed the effects of the number of treatments with cement and the concentration of calcium chloride on the immobilization of Cd by MICP and combined treatments. The results showed that early-stage MICP could immobilize exchangeable cadmium and increase the residual cadmium content, especially with high-concentration calcium chloride MICP treatment. However, in the later stage, soil nitrification and exchange processes led to the dissolution of carbonate-bound cadmium and cadmium activation. The fixing effect of MICP influence whether the MICP-MgO-biochar is superior to the MgO-biochar. Four treatments with cement were more effective than single treatment in MICP-biochar-magnesium oxide treatment, and the MICP-biochar-magnesium oxide treatment with four treatments was the most effective, with passivation rates of 40.7% and 46.6% for exchangeable cadmium and bioavailable cadmium, respectively. However, attention should be paid to the increase in soil salinity. The main mechanism of MICP-magnesium oxide-biochar treatment in immobilizing cadmium was the formation of Cd(OH)2, followed by the formation of cadmium carbonate.

Green synthesis of nanomaterials by using plant extracts as reducing and capping agents

An alternative method to conventional synthesis is examined in this review by the use of plant extracts as reducing and capping agents. The use of plant extracts represents an economically viable and environmentally friendly alternative to conventional synthesis. In contrast to previous reviews, this review focuses on the synthesis of nano-compounds utilizing plant extracts, which lack comprehensive reports. In order to synthesize diverse nanostructures, researchers have discovered a sustainable and cost-effective method of harnessing functional groups in plant extracts. Each plant extract is discussed in detail, along with its potential applications, demonstrating the remarkable morphological diversity achieved by using these green synthesis approaches. A reduction and capping agent made from plant extracts is aligned with the principles of green chemistry and offers economic advantages as well as paving the way for industrial applications. In this review, it is discussed the significance of using plant extracts to synthesize nano-compounds, emphasizing their potential to shape the future of nanomaterials in a sustainable and ecologically friendly manner.

The Cd immobilization mechanisms in paddy soil through ureolysis-based microbial induced carbonate precipitation: Emphasis on the coexisting cations and metatranscriptome analysis

Microbial induced carbonate precipitation (MICP) can immobilize metals and reduce their bioavailability. However, little is known about the immobilization mechanism of Cd in the presence of soil cations and the triggered gene expression and metabolic pathways in paddy soil. Thus, microcosmic experiments were conducted to study the fractionation transformation of Cd and metatranscriptome analysis. Results showed that bioavailable Cd decreased from 0.62 to 0.29 mg/kg after 330 d due to the MICP immobilization. This was ascribed to the increase in carbonate bound, Fe-Mn oxides bound, and residual Cd. The underlying immobilization mechanisms could be attributed to the formation of insoluble Cd-containing precipitates, the complexation and lattice substitution with carbonate and Fe, Mn and Al (hydr)oxides, and the adsorption on functional group on extracellular polymers of cell. During the MICP immobilization process, up-regulated differential expression urease genes were significantly enriched in the paddy soil, corresponding to the arginine biosynthesis, purine metabolism and atrazine degradation. The metabolic pathway of bacterial chemotaxis, flagellum assembly, and peptidoglycan biosynthesis and the expression of cadA gene related to Cd excretion enhanced Cd resistance of soil microbiome. Therefore, this study provided new insights into the immobilization mechanisms of Cd in paddy soils through ureolysis-based MICP process.

Sunlight-driven photocatalytic degradation of ciprofloxacin and organic dyes by biosynthesized rGO-ZrO2 nanocomposites

Aquatic ecology has been greatly threatened by the discharge of effluents of textile and antibiotic industries into natural waters. Herein, an efficient and easily recycled reduced graphene oxide/zirconium oxide nanocomposite has been synthesized using banana peel extract (abbreviated as rGO-ZrO₂ in this work). The X-ray diffraction (XRD), field emission scanning electronic microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), Brunauer-Emmett-Teller (BET), UV-visible diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR) spectroscopy were used to analyze the synthesized material. The as-prepared rGO-ZrO₂ nanocomposite was employed as a photocatalyst for the decomposition of rhodamine blue (RhB) and crystal violet (CV) dyes, and ciprofloxacin (CIP) antibiotic by illumination with direct sunlight. The RhB and CV were degraded to maximum extent of around 86 and 90%, respectively, over the rGO-ZrO₂ nanocomposite after exposure to direct sunlight for 120 min. On the other hand, the degradation of CIP was approximately 93.1% over the rGO-ZrO₂ nanocomposite in 240 min under same experimental conditions. Further studies were performed regarding the role of parameters like pH, catalyst dose, and scavengers, in order to understand the superiority of rGO-ZrO₂ nanocomposite in degrading organic pollutants. Moreover, the intermediate products and plausible CIP degradation mechanisms were examined using liquid chromatography-mass spectrometry (LC-MS). Moreover, the catalyst was easily separated from the solution and demonstrated good stability and reusability. The RhB, CV, and CIP removal efficiency were 80%, 83%, and 88%, respectively, after five cycles.

Rapid and label-free detection of Aflatoxin-B1viamicrofluidic electrochemical biosensor based on manganese (III) oxide (Mn3O4) synthesized by co-precipitation route at room temperature

Aflatoxin B1 (AFB1) is the most toxic mycotoxin, naturally occurring in food items, and it causes several types of lethal diseases. Therefore, a rapid and convenient detection method for AFB1 is the first step toward overcoming the effect of AFB1. The current work presents the development of an efficient microfluidic electrochemical-based biosensor using tri-manganese tetroxide nanoparticles (Mn₃O₄nps) for AFB1 detection. The Mn₃O₄nps were synthesized at room temperature through the co-precipitation route. Its phase purity, structural and morphological studies have been characterized through x-ray diffraction, Raman spectroscopy, energy-dispersive x-ray, Fourier transform infrared spectroscopy and transmission electron microscopy. The mask-less UV-lithography was carried out to fabricate the three-electrode chip and microfluidic channel of the microfluidic electrochemical biosensing system. The designed microfluidic immunosensor (BSA/Ab-AFB1/Mn₃O₄/ITO) was fabricated using the three-electrode chip, microfluidic channel in poly-dimethyl siloxane. The fabricated sensor exhibited the 3.4μA ml ng^-1cm^-2sensitivity and had the lowest lower detection limit of 0.295 pg ml^-1with the detection range of 1 pg ml^-1to 300 ng ml^-1. Additionally, the spiked study was also performed with this immunoelectrode and a recovery rate was obtained of 108.2%.

Dynamic green synthesis of iron oxide and manganese oxide nanoparticles and their cogent antimicrobial, environmental and electrical applications

The scientific community is inclined towards addressing environmental and energy concerns through sustainable means. Conventional processes such as chemical synthesis, involve the usage of environmentally harmful ligands and high tech facilities, which are time-consuming, expensive, energy-intensive, and require extreme conditions for synthesis. Plant-based synthesis is valuable and sustainable for the ecosystem. The use of plant-based precursors for nanoparticle synthesis eliminates the menace of toxic waste contamination. The present review elucidates that the plant based synthesized iron oxide and manganese oxide nanoparticles have tremendous and exceptional applications in various fields such as antimicrobial and antioxidative domains, environmental, electrical and sensing properties. Hence, the literature reviewed explains that plant based synthesis of nanoparticles is an adept and preferred technique. These important transition oxide metal nanoparticles have great applicability in ecological, environmental science as well as electrochemistry and sensing technology. Both these metal oxides display a stable and adaptable nature, which can be functionalized for a specific application, thus exhibiting great potential for efficiency. The current review epitomizes all the latest reported work on the synthesis of iron and manganese oxide nanoparticles through a greener approach along with explaining various significant applications keeping in view the concept of sustainability.

Socio-Economic and Environmental Impacts of Biomass Valorisation: A Strategic Drive for Sustainable Bioeconomy

In the late twentieth century, the only cost-effective opportunity for waste removal cost at least several thousand dollars, but nowadays, a lot of improvement has occurred. The biomass and waste generation problems attracted concerned authorities to identify and provide environmentally friendly sustainable solutions that possess environmental and economic benefits. The present study emphasises the valorisation of biomass and waste produced by domestic and industrial sectors. Therefore, substantial research is ongoing to replace the traditional treatment methods that potentially acquire less detrimental effects. Synthetic biology can be a unique platform that invites all the relevant characters for designing and assembling an efficient program that could be useful to handle the increasing threat for human beings. In the future, these engineered methods will not only revolutionise our lives but practically lead us to get cheaper biofuels, producing bioenergy, pharmaceutics, and various biochemicals. The bioaugmentation approach concomitant with microbial fuel cells (MFC) is an example that is used to produce electricity from municipal waste, which is directly associated with the loading of waste. Beyond the traditional opportunities, herein, we have spotlighted the new advances in pertinent technology closely related to production and reduction approaches. Various integrated modern techniques and aspects related to the industrial sector are also discussed with suitable examples, including green energy and other industrially relevant products. However, many problems persist in present-day technology that requires essential efforts to handle thoroughly because significant valorisation of biomass and waste involves integrated methods for timely detection, classification, and separation. We reviewed and proposed the anticipated dispensation methods to overcome the growing stream of biomass and waste at a distinct and organisational scale.

Electrochemical energy storage electrodes from fruit biochar

This review investigates the electrochemical energy storage electrode (EESE) as the most important part of the electrochemical energy storage devices (EES) prepared from fruit-derived carbon. The EES devices include batteries, supercapacitors, and hybrid devices that have various regular and advanced applications. The preparation of EESE from fruit wastes not only reduce the price of the electrode but also lead to enhance the electrochemical properties of the electrode. The astonishing results of fruits biochar at electrochemical analyses guarantee the performance of these electrodes as EESE. Also, using fruit waste as the precursor of the EESE due to protect the environment and reduce environmental pollutions.

Disposable electrodes from waste materials and renewable sources for (bio)electroanalytical applications

The numerous advantages of disposable and screen-printed electrodes (SPEs) particularly in terms of portability, sensibility, sensitivity and low-cost led to the massive application of these electroanalytical devices. To limit the electronic waste and recover precious materials, new recycling processes were developed together with alternative SPEs fabrication procedures based on renewable, biocompatible sources or waste materials, such as paper, agricultural byproducts or spent batteries. The increased interest in the use of eco-friendly materials for electronics has given rise to a new generation of highly performing green modifiers. From paper based electrodes to disposable electrodes obtained from CD/DVD, in the last decades considerable efforts were devoted to reuse and recycle in the field of electrochemistry. Here an overview of recycled and recyclable disposable electrodes, sustainable electrode modifiers and alternative fabrication processes is proposed aiming to provide meaningful examples to redesign the world of disposable electrodes.

Production of High-Value Nanoparticles via Biogenic Processes Using Aquacultural and Horticultural Food Waste

The quantities of organic waste produced globally by aquacultural and horticulture are extremely large and offer an attractive renewable source of biomolecules and bioactive compounds. The availability of such large and diverse sources of waste materials creates a unique opportunity to develop new recycling and food waste utilisation strategies. The aim of this review is to report the current status of research in the emerging field of producing high-value nanoparticles from food waste. Eco-friendly biogenic processes are quite rapid, and are usually carried out at normal room temperature and pressure. These alternative clean technologies do not rely on the use of the toxic chemicals and solvents commonly associated with traditional nanoparticle manufacturing processes. The relatively small number of research articles in the field have been surveyed and evaluated. Among the diversity of waste types, promising candidates and their ability to produce various high-value nanoparticles are discussed. Experimental parameters, nanoparticle characteristics and potential applications for nanoparticles in pharmaceuticals and biomedical applications are discussed. In spite of the advantages, there are a number of challenges, including nanoparticle reproducibility and understanding the formation mechanisms between different food waste products. Thus, there is considerable scope and opportunity for further research in this emerging field.

Oriented Growth of α-MnO₂ Nanorods Using Natural Extracts from Grape Stems and Apple Peels

We report on the synthesis of alpha manganese dioxide (α-MnO₂) nanorods using natural extracts from Vitis vinifera grape stems and Malus domestica ‘Cortland’ apple peels. We used a two-step method to produce highly crystalline α-MnO₂ nanorods: (1) reduction of KMnO₄ in the presence of natural extracts to initiate the nucleation process; and (2) a thermal treatment to enable further solid-state growth of the nuclei. Transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM) images provided direct evidence of the morphology of the nanorods and these images were used to propose nucleation and growth mechanisms. We found that the α-MnO₂ nanorods synthesized using natural extracts exhibit structural and magnetic properties similar to those of nanoparticles synthesized via traditional chemical routes. Furthermore, Fourier transform infrared (FTIR) shows that the particle growth of the α-MnO₂ nanorods appears to be controlled by the presence of natural capping agents during the thermal treatment. We also evaluated the catalytic activity of the nanorods in the degradation of aqueous solutions of indigo carmine dye, highlighting the potential use of these materials to clean dye-polluted water.

Dietary supplementation of green synthesized manganese-oxide nanoparticles and its effect on growth performance, muscle composition and digestive enzyme activities of the giant freshwater prawn Macrobrachium rosenbergii

The green synthesized Mn3O4 nanoparticles (manganese-oxide nanoparticles) using Ananas comosus (L.) peel extract was characterized by various techniques. HR-SEM photograph showed that manganese-oxide nanoparticles (Mn-oxide NPs) were spherical in shape, with an average size of 40-50 nm. The Zeta potential revealed the surface charge of Mn-oxide NPs to be negative. Further, the Mn-oxide NPs were dietary supplemented for freshwater prawn Macrobrachium rosenbergii. The experimental basal diets were supplemented with Mn-oxide NPs at the rates of 0 (control), 3.0, 6.0, 9.0, 12, 15 and 18 mg/kg dry feed weight. The as-supplemented Mn-oxide NPs were fed in M. rosenbergii for a period of 90 days. The experimental study demonstrated that prawns fed with diet supplemented with 3-18 mg Mn-oxide NPs/kg shows enhanced (P<0.05) growth performance, including final weight and weight gain (WG). Significant differences (P<0.05) in feed conversion ratio (FCR) were observed in prawn fed with different diets. Additionally, prawns fed with 3.0-18 mg/kg Mn-oxide NPs supplemented diets achieved significant (P<0.05) improvement in growth performance, digestive enzyme activities and muscle biochemical compositions, while, the prawns fed with 16 mg/kg of Mn-oxide NPs showed enhanced performance. Prawns fed on diet supplemented with 16 mg/kg Mn-oxide NPs showed significantly (P<0.05) higher total protein level. The antioxidants enzymatic activity (SOD and CAT) metabolic enzymes status in muscle and hepatopancreas showed no significant (P>0.05) alterations in prawns fed with 3.0-18 mg/kg of Mn-oxide NPs supplemented diets. Consequently, the present work proposed that 16 mg/kg of Mn-oxide NPs could be supplemented for flexible enhanced survival, growth and production of M. rosenbergii. Therefore, the data of the present study recommend the addition of 16 mg/kg of Mn-oxide NPs diet to developed prawn growth and antioxidant defense system.

Valorization of banana peel: a biorefinery approach

Banana peel (BP) is an agrowaste produced in large volumes annually, especially by food-processing industries; however, its disposal is of significant concern. However, recent research suggests that BP is a valuable source of bioactive compounds, which can be converted into value-added products. This article reviews the conversion process of value-added products from BP and provides an outline on the chemical composition of BP and its possible applications. In addition, we also discuss the utilization of BP as a substrate to produce animal feed, biofertilizer, dietary fibers, clean energy, industrial enzymes, as well as its use in the synthesis of nanomaterials. Based on the research conducted so far, it is obvious that BP has a wide variety of applications, and thus, developing a biorefinery approach to adequately utilize BP will help realize its economic benefits to the fullest. Based on the valorization of BP, a scheme for BP biorefinery has been proposed. A material balance for BP biorefinery for 1-ton bone-dry BP is presented and our results show that 432 kg of protein or 170 kg of citric acid, 170 kg of pectin, 325 m

Biomorphic synthesis of mesoporous Co₃O₄ microtubules and their pseudocapacitive performance

A novel meosoporous tubular Co3O4 has been fabricated by a simple and cost-effective biomorphic synthesis route, which consists of infiltration of cotton fiber with cobalt nitrate solution and postcalcination at 673 K for 1 h. Its electrochemical performance as a supercapacitor electrode material is investigated by means of cyclic voltammetry and chronopotentiometry tests. Compared with bulk Co3O4 prepared without using cotton template, biomorphic Co3O4 displays 2.8 fold enhancement of pseudocapacitive performance because of the unique tubular morphology, relative high specific surface area (3 and 0.8 m(2)/g for biomorphic Co3O4 and bulk Co3O4, respectively), and mesoporous nature.