Bacteria immobilization on neem leaves/MnFe2O4 composite surface for removal of As(III) and As(V) from wastewater

Removal of Heavy Metals by Pseudomonas sp. - Model Fitting and Interpretation

Industrial and urban modernization processes generate significant amounts of heavy metal wastewater, which brings great harm to human production and health. The biotechnology developed in recent years has gained increasing attention in the field of wastewater treatment due to its repeatable regeneration and lack of secondary pollutants. Pseudomonas, being among the several bacterial biosorbents, possesses notable benefits in the removal of heavy metals. These advantages encompass its extensive adsorption capacity, broad adaptability, capacity for biotransformation, potential for genetic engineering transformation, cost-effectiveness, and environmentally sustainable nature. The process of bacterial adsorption is a complex phenomenon involving several physical and chemical processes, including adsorption, ion exchange, and surface and contact phenomena. A comprehensive investigation of parameters is necessary in order to develop a mathematical model that effectively measures metal ion recovery and process performance. The aim of this study was to explore the latest advancements in high-tolerance Pseudomonas isolated from natural environments and evaluate its potential as a biological adsorbent. The study investigated the adsorption process of this bacterium, examining key factors such as strain type, contact time, initial metal concentration, and pH that influenced its effectiveness. By utilizing dynamic mathematical models, the research summarized the biosorption process, including adsorption kinetics, equilibrium, and thermodynamics. The findings indicated that Pseudomonas can effectively purify water contaminated with heavy metals and future research will aim to enhance its adsorption performance and expand its application scope for broader environmental purification purposes.

MnO2 decoration onto the guava leaves: A sustainable and cost-effective material for methylene blue dye removal

Excessive number of dyes in water is becoming the main cause of water pollution, which is very important to remove because it is harmful. Dye contaminated water is being treated by various methods. Adsorption method can be considered best for the study of dye removal due to several technological reasons. The adsorption method has also been emphasized in this study. In the present work, a nano-bio-composite was fabricated by growing manganese oxide nanoparticles on abundant cellulosic guava leaf powder. This allows nanocomposite to be prepared in large quantities at nominal cost. The characterization technique confirmed the irregular growth of manganese oxide nanoparticles onto the guava leaf powder. The electrostatic and non-electrostatic interactions was confirmed in between manganese oxide nanoparticles and the carbon structure of guava leaf powder. The massive functional groups were found to be in the prepared nano-bio-composite. The grain size of prepared material was in nano range. The developed nano-bio-composite was used to remove methylene blue from water. This showed a very good adsorptive capacity for methylene blue. The analyzed adsorption data was modelled through isotherms, kinetics and thermodynamics models. The nature of the adsorption process was determined to be spontaneous and exothermic. The reusability test was carried out for five adsorption-desorption cycles. The reusability results suggested the better removal efficiency (%) in the first two cycles with only 20 % reduction in removal efficiency (%). The leaching test result revealed the good stability of MnO2/GL at neutral pH. It was a unique and cheap adsorbent of its kind, which had not been noticed anywhere before.

Immobilization of Microbes for Biodegradation of Microcystins: A Mini Review

Harmful cyanobacterial blooms (HCBs) frequently occur in eutrophic freshwater ecosystems worldwide. Microcystins (MCs) are considered to be the most prominent and toxic metabolites during HCBs. MCs may be harmful to human and animal health through drinking water and recreational water. Biodegradation is eco-friendly, cost-effective and one of the most effective methods to remove MCs. Many novel MC-degrading bacteria and their potential for MCs degradation have been documented. However, it is a challenge to apply the free MC-degrading bacterial cells in natural environments due to the long-term operational instability and difficult recycling. Immobilization is the process of restricting the mobility of bacteria using carriers, which has several advantages as biocatalysts compared to free bacterial cells. Biological water treatment systems with microbial immobilization technology can potentially be utilized to treat MC-polluted wastewater. In this review article, various types of supporting materials and methods for microbial immobilization and the application of bacterial immobilization technology for the treatment of MCs-contaminated water are discussed. This article may further broaden the application of microbial immobilization technology to the bioremediation of MC-polluted environments.

Optimization of multiple parameters for adsorption of arsenic (III) from aqueous solution using Psidium guajava leaf powder

The conventional method of water treatment using activated carbon from several sources has been focused on extensively in the last two decades. However, rare attention has been noticed on natural adsorbents such as plant leaves. Therefore, the Psidium guajava (guava) leaf has been investigated to understand its adsorption efficacy for Arsenic (III) [As(III)] in this study. The effect of process variables, e.g., pH, concentration of metal ion, adsorbent's particle size, and dosages, are evaluated. Experiments are carried out in batch mode, and the individual and combined parameter's impact on adsorption have been discussed. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) is used to characterize the adsorbent's surface. Freundlich and Langmuir's isotherms are used for adsorption equilibrium study. The adsorption parameters are optimized by establishing a regression correlation using central composite design (CCD) of response surface methodology (RSM). The analysis of variance (ANOVA) suggests a high regression coefficient (R² = 0.9249) for the removal of As(III). Particle size of 0.39 mm; adsorbent's height of 10 cm; metal ion concentration of 30 ppm, and pH 6 are optimized to remove 90.88% As(III) from aqueous solution. HCl is evaluated as a potential solvent for desorption of arsenic from the desorption study.

Removal of ibuprofen from aqueous media by adsorption: A comprehensive review

Ibuprofen (IBP) is a non-steroidal anti-inflammatory drug released into the environment through hospital and medical effluents, pharmaceutical wastewater and veterinary use. The aim of this paper is to review the empirical findings on the adsorption of IBP from aqueous media. A preliminary ecotoxicological assessment confirmed the environmental risk of IBP in the aqueous environment. Open literature works considered in this review were for the past decade (2010-2020). Carbon-based adsorbents are the best class of adsorbent for the uptake of IBP and the highest reported maximum adsorption capacity (q_max) for IBP is 496.1 mg/g by SWCNTs. The range of adsorption capacities for IBP uptake in this review is between 0.0496 and 496.1 mg/g. The mechanism of uptake is majorly by hydrophobic interactions, π - π stacking, hydrogen bonds, electrostatic interactions and dipole-dipole interaction. IBP uptake was best fit to a wide variety of isotherm models but was well suited to the pseudo-second order kinetics model. The thermodynamics of IBP uptake depends majorly on the nature of the adsorbent and desorption from the solid phase is based on an appropriate choice of the eluent. Knowledge gaps were observed in used adsorbent disposal and process improvement. In the future, interest would increase in scale-up, industrial applications and practical utilisation of the research findings which would help in sustainable water resource management.

Testing of Chemically Activated Cellulose Fibers as Adsorbents for Treatment of Arsenic Contaminated Water

Exposure to different arsenic concentrations (higher than 10 μg/L), either due to the direct consumption of contaminated drinking water or indirectly by using contaminated food is harmful for human health. Therefore, it is important to remove arsenic from aqueous solutions. Among many arsenic removal technologies, adsorption offers a promising solution with a good efficiency, however the material used as adsorbent play a very vital role. The present investigation evaluated the behavior of two cellulose-based adsorbent materials, i.e., viscose fibers (V) and its TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) derivative, obtained by using the well-established TEMPO-mediated protocol (VF). Due to the known arsenic affinity for Fe ions the two materials were later doped with it. This was done after a preliminary functionalization with di-2-ethylhexyl phosphoric acid (DEHPA), to obtain two materials: V-DEHPA-Fe and VF-DEHPA-Fe. Arsenic adsorption is known to be pH dependent (between 6 and 8); therefore, the optimal pH range for As(V) adsorption has been established. In order to evaluate the adsorption mechanism for both the synthesized materials, the influence of contact time, temperature and initial concentration was evaluated. Langmuir, Freundlich and Sips equilibrium isotherm models were used in order to determine the ability of the model to describe As(V) adsorption process. The maximum adsorption capacity of the material V-DEHPA-Fe was 247.5 µg As(V)/g with an As(V) initial concentration of 5 mg/L and for the material VF-DEHPA-Fe it was 171.2 µg As(V)/g with initial concentration of 5 mg/L.

Kinetic modelling of the uranium biosorption by Deinococcus radiodurans biofilm

Increasing number of reports on uranium contamination in groundwater bodies is a growing concern. Deinococcus radiodurans biofilm-based U(VI) bioremediation has great potential to provide solution. This study focuses on the kinetic modelling of uranium biosorption by D. radiodurans biofilm biomass and identification of the functional groups involved in the sequestration process. The effect of temperature, pH and amount of biofilm dry mass were studied using two uranyl ion concentrations (100 and 1000 mg/L). D. radiodurans dry biomass showed good affinity for uranyl ion adsorption. The kinetic experiments revealed that the biosorption process was spontaneous and exothermic in nature. The modelling of kinetic adsorption data revealed that U(VI) sorption by D. radiodurans biofilm biomass follows a pseudo-second-order reaction. Mechanism of U(VI) sorption was suggested to follow an intra-particle diffusion model, which includes covalent bonding between U(VI) and functional groups present on the surface of biofilm biomass, and diffusional barrier acts as a rate limiting step. External mass transfer was the rate-limiting step as evident from Boyd and Elovich plot. Chemical modifications in surface functional groups of biofilm biomass, confirmed the involvement of carboxyl, phosphate, and hydroxyl groups in uranium binding as a significant loss in U(VI) sorption capacity was recorded in these chemically modified biomasses. XRD data indicated the formation of metal deposits, predominantly as uranyl phosphates.

A novel self-crosslinked gel microspheres of Premna microphylla turcz leaves for the absorption of uranium

Premna microphylla turcz leaves (PMTL) is a resource-rich, biodegradable, renewable biomass. Here, a microsphere adsorbent was prepared from PMTL by a self-crosslinking method without any addition of chemical cross-linking agent, and characterized by SEM, FTIR, and XPS. The influence of preparation methods and conditions on the properties of the microspheres was studied and the self-crosslinking mechanism was analyzed. The effects of temperature, pH, contact time, uranium concentration, and adsorbent dosage on its adsorption performance toward to uranium were systematically explored. The results showed that PMTL endogenous pectin binding with endogenous Ca²⁺, Mg²⁺ and other metal ions to form an 'egg box' structure might be the mechanism of its self-crosslinking to form microspheres. The adsorption isotherms fitted well by the Freundlich model and the experimental maximum adsorption capacity of microspheres was 346.65 mg·g^-1 at pH of 5, and kinetics data correlated well with the pseudo-second order model. The adsorption mechanism might be the coordination bonding between the uranium and oxygen-containing groups (hydroxyl and carboxyl groups), and the ion exchange between the uranium and metal ions (mainly Ca²⁺ and Mg²⁺). The PMTL microspheres are promising in treating uranium-containing wastewater in a more cost-effective and environmentally friendly manner.