Spirulina platensis mediated biosynthesis of Cuo Nps and photocatalytic degradation of toxic azo dye Congo red and kinetic studies

Microalgae as a potential natural source for the green synthesis of nanoparticles

The increasing global population is driving the development of alternative sources of food and energy, as well as better or new alternatives for health and environmental care, which represent key challenges in the field of biotechnology. Microalgae represent a very important source material to produce several high-value-added bioproducts. Due to the rapid changes in the modern world, there is a need to build new materials for use, including those in the nanometer size, although these developments may be chronological but often do not occur at a time. In the last few years, a new frontier has opened up at the interface of biotechnology and nanotechnology. This new frontier could help microalgae-based nanomaterials to possess new functions and abilities. Processes for the green synthesis of nanomaterials are being investigated, and the availability of biological resources such as microalgae is continuously being examined. The present review provides a concise overview of the recent advances in the synthesis, characterization, and applications of nanoparticles formed using a wide range of microalgae-based biosynthesis processes. Highlighting their innovative and sustainable potential in current research, our study contributes towards the in-depth understanding and provides latest updates on the alternatives offered by microalgae in the synthesis of nanomaterials.

Photocatalytic activity of the biogenic mediated green synthesized CuO nanoparticles confined into MgAl LDH matrix

The global concern over water pollution caused by organic pollutants such as methylene blue (MB) and other dyes has reached a critical level. Herein, the Allium cepa L. peel extract was utilized to fabricate copper oxide (CuO) nanoparticles. The CuO was combined with MgAl-layered double hydroxides (MgAl-LDHs) via a co-precipitation method with varying weight ratios of the CuO/LDHs. The composite catalysts were characterized and tested for the degradation of MB dye. The CuO/MgAl-LDH (1:2) showed the highest photocatalytic performance and achieved 99.20% MB degradation. However, only 90.03, 85.30, 71.87, and 35.53% MB dye was degraded with CuO/MgAl-LDHs (1:1), CuO/MgAl-LDHs (2:1), CuO, and MgAl-LDHs catalysts, respectively. Furthermore, a pseudo-first-order rate constant of the CuO/MgAl-LDHs (1:2) was 0.03141 min-1 while the rate constants for CuO and MgAl-LDHs were 0.0156 and 0.0052 min-1, respectively. The results demonstrated that the composite catalysts exhibited an improved catalytic performance than the pristine CuO and MgAl-LDHs. The higher photocatalytic performances of composite catalysts may be due to the uniform distribution of CuO nanoparticles into the LDH matrix, the higher surface area, and the lower electron and hole recombination rates. Therefore, the CuO/MgAl-LDHs composite catalyst can be one of the candidates used in environmental remediation.

Efficient photodegradation of methyl red dye by kaolin clay supported zinc oxide nanoparticles with their antibacterial and antioxidant activities

Kaolin clay-supported Zinc oxide (ZnO/KC) and ZnO NPs nanoparticles (NPs) were prepared by a chemical reduction process and used for the photodegradation of methyl red (MR) dye as a photocatalyst. Due to the interlayered porous structure of the KC, we achieved an extremely good association between ZnO NPs and KC. The product confirmation was conducted by Scanning electron microscopy (SEM), X-Ray diffraction (XRD), energy dispersive X-Ray (EDX), and Fourier transforms infrared (FTIR). SEM showed the irregular morphology of ZnO NPs, while ZnO/KC NCs were predominately round-shaped. Moreover, in both cases, NPs were present in both dispersed as well as agglomerated forms with an average particle size below 100 nm. The results acquired from photodegradation analyses show that ZnO NPs and ZnO/KC NCs degraded about 90 and 99% of MR dye respectively, under UV light in a short irradiation time of 10 min. The recovered and re-recovered ZnO NPs and ZnO/KC NCs also considerably photodegraded MR dye in an aqueous medium. The same NPs also exhibit promising bioactivities against two pathogenic bacteria, i.e., Citrobacter and Providencia. The antioxidant activity of ZnO/KC NCs reached to reasonable 70% compared to the 88% activity of the standard ascorbic acid.

Cyanoremediation and phyconanotechnology: cyanobacteria for metal biosorption toward a circular economy

Cyanobacteria are widespread phototrophic microorganisms that represent a promising biotechnological tool to satisfy current sustainability and circularity requirements. They are potential bio-factories of a wide range of compounds that can be exploited in several fields including bioremediation and nanotechnology sectors. This article aims to illustrate the most recent trends in the use of cyanobacteria for the bioremoval (i.e., cyanoremediation) of heavy metals and metal recovery and reuse. Heavy metal biosorption by cyanobacteria can be combined with the consecutive valorization of the obtained metal-organic materials to get added-value compounds, including metal nanoparticles, opening the field of phyconanotechnology. It is thus possible that the use of combined approaches could increase the environmental and economic feasibility of cyanobacteria-based processes, promoting the transition toward a circular economy.

Removal of hydrocarbons and heavy metals from petroleum water by modern green nanotechnology methods

Considered heavy metals, such as As(III), Bi(II), Cd(II), Cr(VI), Mn(II), Mo(II), Ni(II), Pb(II), Sb(III), Se(-II), Zn(II), and contaminating chemical compounds (monocyclic aromatic hydrocarbons such as phenolic or polycyclic derivatives) in wastewater (petrochemical industries: oil and gas production plants) are currently a major concern in environmental toxicology due to their toxic effects on aquatic and terrestrial life. In order to maintain biodiversity, hydrosphere ecosystems, and people, it is crucial to remove these heavy metals and polluting chemical compounds from the watery environment. In this study, different Nanoparticles (α-Fe₂O₃, CuO, and ZnO) were synthesized by green synthesis method using Portulaca oleracea leaf extract and characterized by UV-Vis spectrophotometers, FTIR spectroscopy, X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) techniques in order to investigate morphology, composition, and crystalline structure of NPs, these were then used as adsorbent for the removal of As(III), Bi(II), Cd(II), Cr(VI), Mn(II), Mo(II), Ni(II), Pb(II), Sb(III), Se(-II), and Zn(II) from wastewater, and removal efficiencies of were obtained 100% under optimal conditions.

Facile fabrication of mesoporous carbon-anchored cobalt ferrite nanoparticles as a heterogeneous activator of peroxymonosulfate for efficient degradation of Congo red

Herein, mesoporous carbon-anchored cobalt ferrite nanocomposites (nano-CoFe₂O₄@MC) were fabricated using a hydrothermal method for application as heterogeneous catalysts to activate peroxymonosulfate (PMS), in order to solve the problems of low activation performance and secondary pollution caused by the inter-particle agglomeration, metal ion leaching, and difficult recovery of nano metal catalysts. Analysis techniques such as SEM, TEM, XRD, BET, FTIR, VSM, TGA, and Raman spectroscopy indicated that the prepared nanocomposites have excellent surface properties, structural stability, and magnetic properties. The performance of nano-CoFe₂O₄@MC for Congo red (CR) degradation was evaluated by comparison with other treatment systems and study of the influence of experimental parameters, including the anchoring ratios, catalyst dosage, PMS concentration, initial pH, CR concentration, coexisting anions, and humic acid. Both radical and nonradical pathways were observed in the activation process of PMS by nano-CoFe₂O₄@MC. The analysis results of the element composition and ionic state of the catalyst show that the redox cycle of two ion pairs, Co³⁺/Co²⁺ and Fe²⁺/Fe³⁺, could enhance the multipath electron transfer on the catalyst surface to promote the generation of reactive oxygen species. Identification of the intermediate products revealed CR was transformed into 12 intermediates through two branch pathways in the nano-CoFe₂O₄@MC/PMS system. After five cycles of use, the catalytic efficiency of the catalyst did not decrease significantly. Nanocomposites with high catalytic performance, stability, recyclability, and a low ion leaching rate have broad application prospects in the treatment of antibiotic wastewater.

Synthesis of Green Magnetite/Carbonized Coffee Composite from Natural Pyrite for Effective Decontamination of Congo Red Dye: Steric, Synergetic, Oxidation, and Ecotoxicity Studies

Green magnetite/carbonized spent coffee (MG/CFC) composite was synthesized from natural pyrite and characterized as an adsorbent and catalyst in photo-Fenton’s oxidation system of Congo red dye (C.R). The absorption behavior was illustrated based on the steric and energetic parameters of the advanced Monolayer equilibrium model of one energetic site (R2 > 0.99). The structure exhibits 855 mg/g as effective site density which induces its C.R saturation adsorption capacity to 436.1 mg/g. The change in the number of absorbed C.R per site with temperature (n = 1.53 (293) to 0.51 (313 K)) suggests changes in the mechanism from multimolecular (up to 2 molecules per site) to multianchorage (one molecule per more than one site) processes. The energetic studies (ΔE = 6.2–8.2 kJ/mol) validate the physical uptake of C.R by MG/CFC which might be included van der Waals forces, electrostatic attractions, and hydrogen bonding. As a catalyst, MG/CFC exhibits significant activity during the photo-Fenton’s oxidation of C.R under visible light. The complete oxidation of C.R was detected after 105 min (5 mg/L), 120 min (10 mg/L), 135 min (15 mg/L), 180 min (20 mg/L), and 240 min (25 mg/L) using MG/CFC at 0.2 g/L dosage and 0.1 mL of H2O2. Increasing the dosage up to 0.5 g/L reduce the complete oxidation interval of C.R (5 mg/L) down to 30 min while the complete mineralization was detected after 120 min. The acute and chronic toxicities of the treated samples demonstrate significant safe products of no toxic effects on aquatic organisms as compared to the parent C.R solution.

Scavenging of Organic Pollutant and Fuel Generation through Cost-Effective and Abundantly Accessible Rust: A Theoretical Support with DFT Simulations

Waste management and energy generation are the foremost concerns due to their direct relationship with biological species and the environment. Herein, we report the utilization of iron rust (inorganic pollutant) as a photocatalyst for the photodegradation of methylene blue (MB) dye (organic pollutant) under visible light (economic) and water oxidation (energy generation). Iron rust was collected from metallic pipes and calcined in the furnace at 700 °C for 3 h to remove the moisture/volatile content. The uncalcined and calcined rust NPs are characterized through scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Fourier-transform infrared (FTIR) analysis, X-ray Diffraction (XRD), and thermogravimetric analysis (TGA). The morphological study illustrated that the shape of uncalcined and calcined iron rust is spongy, porous, and agglomerated. The XRD and DLS particle sizes are in a few hundred nanometers range. The photodegradation (PD) investigation shows that calcined rust NPs are potent for the PD of modeled MB, and the degradation efficiency was about 94% in a very short time of 11 min. The photoelectrochemical (PEC) measurements revealed that calcined rust NPs are more active than uncalcined rust under simulated 1 SUN illumination with the respective photocurrent densities of ~0.40 and ~0.32 mA/cm². The density functional theory simulations show the chemisorption of dye molecules over the catalyst surface, which evinces the high catalytic activity of the catalyst. These results demonstrate that cheaper and abundantly available rust can be useful for environmental and energy applications.

Amine-functionalized MOF-derived carbon materials for efficient removal of Congo red dye from aqueous solutions: simulation and adsorption studies

In this study, a novel polyethyleneimine (PEI) modified MOF-derived carbon adsorbent (PEI@MDC) was proposed, which exhibited significant adsorption capacity for Congo Red (CR) in aqueous solutions. FT-IR and XPS results showed that PEI was successfully grafted onto MDC, increasing the content of amine groups on the surface of MDC. The adsorption process conformed to the Langmuir isotherm adsorption model and pseudo-second-order kinetic equation, indicating that the adsorption of CR on PEI@MDC was covered by a single layer, and the adsorption process was controlled by chemical processes. According to the Langmuir model, the maximum adsorption capacity at 30 °C was 1723.86 mg g^-1. Hydrogen bonding and electrostatic interactions between CR and PEI@MDC surface functional groups were the main mechanisms controlling the adsorption process. After five adsorption-desorption cycles, PEI@MDC still showed a high adsorption capacity for CR, indicating that the adsorbent had an excellent regeneration ability.

Biosynthesis and extrinsic toxicity of copper oxide nanoparticles against cattle parasites: An eco-friendly approach

Plant extracts' ability to collect metals and decrease metal ions makes them a superior candidate for the biosynthesis of nanoparticles; hence, they are referred to as bio-nano factories since both living and dead dried biomass are employed to produce metallic nanoparticles. The antiparasitic activity of biosynthesized copper oxide nanoparticles (CuO NPs) was examined against cow tick larvae (Rhipicephalus microplus, Haemaphysalis bispinosa, and Hippobosca maculata). These parasitic larvae were treated with various concentrations of methanolic leaf extract of A. marmelos (MLE-AM) and biosynthesized CuO NPs for 24 h. CuO NPs were synthesized quickly using A. marmelos leaf extract, and nanoparticle synthesis was identified within 15 min. The results from characteristic XRD, FTIR, SEM, EDX, and TEM analyses confirmed the biosynthesis of CuO NPs. The presence of 26-Hydroxycholesterol was discovered as the predominant chemical present in the GC-MS analysis of MLE-AM. The maximum efficacy was observed in biosynthesized CuO NPs against R. microplus larvae, H. bispinosa adults, and Hip. maculata larvae (LC₅₀ = 4.30, 9.50, and 11.13 mg/L; and LC₉₀ = 8.30, 19.57, and 21.65 mg/L; and 6.219, 6.547, and 2.587). Overall, the bio-fabrication of CuO NPs has the potential to develop better and safer antiparasitic control techniques.

Enhanced Congo Red Adsorption and Photo-Fenton Oxidation over an Iron-Impeded Geopolymer from Ferruginous Kaolinite: Steric, Energetic, Oxidation, and Synergetic Studies

An iron-impeded geopolymer (Fe/GP) was synthesized from natural ferruginous kaolinite and optical waste for enhanced decontamination of Congo red (CR) dye. The adsorption properties of Fe/GP were assessed using an advanced monolayer equilibrium model of one energy (R ² > 0.99). Fe/GP possessed an active site density of 391.3 mg/g, which induced an adsorption capacity of 634 mg/g at the saturation state. The number of adsorbed CR molecules per site (n = 1.56-1.62) reflected the possible uptake of two molecules per site via a multimolecular mechanism. The adsorption energy (5.12-5.7 kJ/mol) reflected the physical adsorption of the CR molecules via hydrogen bonding and/or van der Waals forces. As a catalyst, notable activity toward photo-Fenton oxidation was achieved even at high CR concentrations. Complete oxidation was observed after 30 (CR concentration: 10 mg/L), 50 (20 mg/L), 80 (30 mg/L), 120 (40 mg/L), and 140 min (50 mg/L). High oxidation efficiency was achieved using 0.1 g/L Fe/GP, 0.1 mL of hydrogen peroxide (H₂O₂), and a visible light source. Increasing the Fe/GP dosage to 0.3 g/L resulted in complete oxidation of CR (100 mg/L) after 220 min. Therefore, synthetic Fe/GP can be used as a low-cost and superior catalyst and adsorbent for the removal of CR-based contaminants via adsorption or advanced oxidation processes.

Self-Powered Photoelectrochemical Assay for Hg2+ Detection Based on g-C3N4-CdS-CuO Composites and Redox Cycle Signal Amplification Strategy

A highly sensitive self-powered photoelectrochemical (spPEC) sensing platform was constructed for Hg2+ determination based on the g-C3N4-CdS-CuO co-sensitized photoelectrode and a visible light-induced redox cycle for signal amplification. Through successively coating the single-layer g-C3N4, CdS, and CuO onto the surface of an electrode, the modified electrode exhibited significantly enhanced PEC activity. The microstructure of the material was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). However, the boost in photocurrent could be noticeably suppressed due to the consumption of hole-scavenging agents (reduced glutathione) by the added Hg2+. Under optimal conditions, we discovered that the photocurrent was linearly related to the Hg2+ concentration in the range of 5 pM–100 nM. The detection limit for Hg2+ was 0.84 pM. Moreover, the spPEC sensor demonstrated good performance for the detection of mercury ions in human urine and artificial saliva.

Cyanobacteria: miniature factories for green synthesis of metallic nanomaterials: a review

Nanotechnology is one of the most promising and advanced disciplines of science that deals with synthesis, characterization and applications of different types of Nanomaterials (NMs) viz. nanospheres, nanoparticles, nanotubes, nanorods, nanowires, nanocomposites, nanoalloys, carbon dots and quantum dots. These nanosized materials exhibit different physicochemical characteristics and act as a whole unit during its transport. The unique characteristics and vast applications of NMs in diverse fields viz. electronics, agriculture, biology and medicine have created huge demand of different type of NMs. Conventionally physical and chemical methods were adopted to manufacture NMs which are expensive and end up with hazardous by-products. Therefore, green synthesis exploiting biological resources viz. algae, bacteria, fungi and plants emerged as a better and promising alternative due to its cost effective and ecofriendly approach and referred as nanobiotechnology. Among various living organisms, cyanobacteria have proved one of the most favourable bioresources for NMs biosynthesis due to their survival in diverse econiches including metal and metalloid contaminated sites and capability to withstand high levels of metals. Biosynthesis of metallic NMs is accomplished through bioreduction of respective metal salts by various capping agents viz. alkaloids, pigments, polysaccharides, steroids, enzymes and peptides present in the biological systems. Advancement in the field of Nanobiotechnology has produced large number of diverse NMs from cyanobacteria which have been used as antimicrobial agents against Gram positive and negative human pathogens, anticancer agents, luminescent nanoprobes for imaging of cells, antifungal agents against plant pathogens, nanocatalyst and semiconductor quantum dots in industries and in bioremediation in toxic pollutant dyes. In the present communication, we have reviewed cyanobacteria mediated biosynthesis of NMs and their applications in various fields.