Peculiarities of adsorption of Cr (VI) ions on the surface of Chlorella vulgaris ZBS1 algae cells

Sorption of per- and polyfluoroalkyl substances by lignin in pulp and paper wastewater

Per- and polyfluoroalkyl substances (PFAS) are anthropogenic chemicals commonly found in the environment. PFAS pose multifaceted challenges including identifying sources and exposure pathways, detecting and quantifying their presence, characterizing their fate and transport, and assessing their risks. PFAS and fluorotelomer polymers can be found in the pulp and paper (P&P) wastewater systems, but their behavior remains poorly understood. The constituents of P&P waste include lignin hydrolysis products, hence PFAS interactions with lignin likely affect PFAS removal efforts. This study employed quantitative ultra-performance liquid chromatography triple quadrupole mass spectrometry (UPLC-MS/MS) to investigate the sorption-desorption capacity and mechanisms of PFAS interaction with lignin. PFAS with sulfonate functional groups displayed higher affinity for lignin (solid phase) based on their partitioning coefficient (Kd), while PFAS with carboxylate head groups persisted in the P&P wastewater (aqueous phase). Sorption to lignin exhibited an increase with chain length (CF2)n among compounds with the same functional group. Long-chain (C ≥ 6) PFAS demonstrated higher sorption compared to short-chain (C ≤ 5) homologs. The sorption-desorption capacities, partitioning coefficients, and kinetics of PFAS reported in this study can facilitate predictive models for PFAS and assist in the development of efficient P&P waste treatment and management.

Marine vanadium pollution: Sources, ecological impacts and cutting-edge mitigation strategies

Vanadium (V) is a hazardous element with widespread environmental presence, particularly in marine environments, due to both natural and industrial sources. This review examines vanadium's impact on marine organisms, highlighting its disruption of metabolic processes in fish, microalgae, and crustaceans, leading to oxidative stress, impaired growth and reproduction. Vanadium accumulation in marine food chains poses risks to higher organisms, including humans. Conventional vanadium removal methods, e.g., filtering and reverse osmosis, are costly and energy-intensive. Alternatively, bioremediation offers a sustainable solution, particularly using microalgae and thraustochytrids. Microalgae can detoxify and immobilize vanadium through adsorption and biodegradation, contributing to carbon capture and producing value-added products. Advances in bioprocess engineering, including regulating key parameters such as temperature and pH during biomass harvesting and using chelating agents, have enhanced this bioremediation approach, making it a viable option for industrial-scale applications and aligning with Sustainable Development Goals by integrating environmental protection with renewable energy production.

Silicone-modified black peanut shell (BPS) biochar adsorbents: Preparation and their adsorptions for copper(II) from water

Novel silicone-modified biochar adsorbents (BPS-MBCs) were prepared by utilizing waste black peanut shell (BPS) as a raw biochar and gamma-amino-propyl triethoxysilane (silicone) as an inorganic modifier. The novelty of this work is that the incorporation of silicone into BPS can rise the specific surface area and porosity of BPS-MBCs and elevate their adsorptions for copper (II). Sorption kinetics data for copper (II) were molded using five kinetic equations [i.e. Lagergren 1st-order and 2nd-order, intraparticle diffusion (IN-D), Elovich, and Diffusion-chemisorption]. The equilibrium adsorption data for copper (II) were analyzed using two-parameter isotherm equations [i.e. Langmuir, Freundlich, Dubinin-Radushkevich, and Temkin] and three-parameter Sips, Redlich-Peterson and Toth isotherm models. It was validated that copper (II) sorption on BPS-MBCs matched better with pseudo-2nd-order kinetic, Diffusion-chemisorption and Langmuir isotherm models. The maximal qmLan of BPS-MBC-400 was near 284 mg/g at 45 °C. By multi-phase fitting of IN-D modelling, intra-particle diffusion coefficient (kin-d) and diffusion coefficient of external mass-transfer (DEx-Di) for copper (II) were calculated. The low sorption energy from Temkin and mean free energy from D-R modellings implied that copper (II) sorption was initiated by weak non-covalent bond interactions. Thermodynamic parameters indicated that copper (II) on BPS-MBCs was an endothermic and spontaneous process. Recycling of BPS-MBC-400 for copper (II) suggested it has excellent reusability. The major mechanism of copper (II) on BPS-MBCs is possibly comprised of multiple processes, such as physical adsorption (electrostatic attraction), chemical adsorption (adsorption from functional groups, chelation, and ion exchange) and diffusion-chemisorption. Based on these findings, it is expects that BPS-MBCs are promising sorbents for copper (II) eradication from Cu(II)-including wastewater.

Sorption of chromium from aqueous solutions using Fucus vesiculosus algae biosorbent

The presence of heavy metals in wastewater is an environmental concern and the current treatment procedures are very expensive so it is necessary to find effective and inexpensive biosorbents. In this study, Fucus vesiculosus was used as a biosorbent for the biosorption of Cr(III) ions from the aqueous solutions. Biosorption parameters, such as pH, adsorbent dose, contact time, and initial concentrations of Cr(III) had the most impact on the sorption process. The required pH value for sorption was 5, the biosorbent dose was 4.0 g/L, the contact time was seen to occur after 90 min, and the Cr(III) removal decreased from 98.9 to 92%. The maximum biosorption capacity of chromium was 14.12 mg/g. FTIR analysis of Fucus vesiculosus biomass before the sorption process contains carboxyl, amino, hydroxyl, alkyne, and carbonyl groups, and according to the analysis after the sorption process, it was found that Cr(III) metal ions were incorporated within the sorbent during the interaction with (=C-H) active functional groups. The biosorption data were found to be perfectly suited by Langmuir equilibrium isotherm model. According to the results of this study, Fucus vesiculosus is an effective biosorbent for the removal of Cr(III) from aqueous solutions.

Effect of extracellular polymeric substances on the colony size and morphological changes of Microcystis

Surface blooms of colony-forming Microcystis are increasingly occurring in aquatic ecosystems on a global scale. Recent studies have found that the Microcystis colonial morphology is a crucial factor in the occurrence, persistence, and dominance of Microcystis blooms, yet the mechanism driving its morphological dynamics has remained unknown. This study conducted a laboratory experiment to test the effect of extracellular polymeric substances on the morphological dynamics of Microcystis. Ultrasound was used to disaggregate colonies, isolating the cells and of the Microcystis suspension. The single cells were then re-cultured under three homologous EPS concentrations: group CK, group Low, and group High. The size, morphology, and EPS [including tightly bound EPS (TB-EPS), loosely bound EPS (LB-EPS), bound polysaccharides (B-polysaccharides), and bound proteins (B-proteins)] changes of colonies were closely monitored over a period of 2 months. It was observed that colonies were rapidly formed in group CK, with median colony size (D50) reaching 183 µm on day 12. The proportion of colonies with a size of 150-500 µm increased from 1% to more than 50%. Colony formation was also observed in both groups Low and High, but their D50 increased at a slower rate and remained around 130 µm after day 17. Colonies with a size of 50-150 µm account for more than 50%. Groups CK and Low successively recovered the initial Microcystis morphology, which is a ring structure formed of several small colonies with a D50 of 130 µm. During the recovery of the colony morphology, the EPS per cell increased and then decreased, with TB-EPS and B-polysaccharides constituting the primary components. The results suggest that colony formation transitioned from adhesion driven to being division driven over time. It is suggested that the homologous EPS released into the ambient environment due to the disaggregation of the colony is a chemical cue that can affect the formation of a colony. This plays an important but largely ignored role in the dynamics of Microcystis and surface blooms.

Hydrothermally magnetic particles fabricated hydrocalumite based biopolymeric composites for toxic chromium removal

Hexavalent chromium is an emerging environmental pollutant that leads to various effects on living organisms. The developed clay material, hydrocalumite (HC) possesses promising chromium adsorption capacity but because of its powder form it cannot be used in column studies. Hence, it is aimed to prepared HC in an usable hybrid bio-composite form by dispersing HC in biopolymeric matrixes like chitosan (CS) and cellulose (Cel) as HCCS and HCCel bio-composites for Cr(VI) removal from water. For quick separation after adsorption, the magnetic particles sprayed HCCS (Fe3O4@HCCS) and HCCel (Fe3O4@HCCel) bio-composites were prepared which possess high adsorption capacity. Different instrumental techniques like FTIR, SEM, and EDAX studies were used to examine the synthesized magnetic bio-composites in order to determine their physicochemical properties. The promising adsorbents namely Fe3O4@HCCS and Fe3O4@HCCel bio-composites were examined for Cr(VI) removal in batch mode. The maximum chromium adsorption capacity of Fe3O4@HCCS and Fe3O4@HCCel bio-composites were found at 43.4 mg/L and 31.8 mg/L, respectively within 45 min. The Freundlich, Langmuir, and Dubinin-Radushkevich (D-R) isotherms were used to reinterpret the equilibrium data of the synthetic magnetic bio-composites. According to the thermodynamic findings, chromium adsorption onto magnetic bio-composites is an endothermic and spontaneous reaction. The NaOH solution makes it simple to regenerate the chromium adsorbed magnetic bio-composites, which can be successfully employed upto four times. The synthesized Fe3O4@HCCS and Fe3O4@HCCel bio-composites act as efficient adsorbents for chromium removal.

In situ prepared Chlorella vulgaris-supported nanoscale zero-valent iron to remove arsenic (III)

Nanoscale zero-valent iron (nZVI) has a high removal affinity toward arsenic (As). However, the agglomeration of nZVI reduces the removal efficiency of As and, thus, limit its application. In this study, we report an environmentally friendly novel composite of Chlorella vulgaris-supported nanoscale zero-valent iron (abbreviated as CV-nZVI) that exhibits a fast and efficient removal of As(III) from As-contaminated water. Scanning electron microscopy-energy-dispersive spectroscopy (SEM-EDS), X-ray diffractometry (XRD), attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR), and X-ray photoelectron spectroscopy (XPS) were used to characterize and analyze the CV-nZVI. These results indicated that the stabilization effect of C. vulgaris reduced the nZVI agglomeration and enhanced the reactivity of nZVI. The experiments showed a removal efficiency of 99.11% for As(III) at an optimum pH of 7.0. The adsorption kinetics and isotherms followed the pseudo-second-order kinetic model and Langmuir adsorption isotherm with the superior maximum adsorption capacities of 34.11 mg/g for As(III). The FTIR showed that the As(III) was adsorbed on the CV-nZVI surface by complexation reaction, and XPS indicated that oxidation reaction was also involved. After five reuse cycles, the removal efficiency of As(III) by CV-nZVI was 32.93%, suggesting that the CV-nZVI had some reusability and regeneration. Overall, this work provides a practical and highly efficient approach for As remediation in As-contaminated water, and simultaneously resolves the agglomeration problems of nZVI nanoparticles.

A review on algae biosorption for the removal of hazardous pollutants from wastewater: Limiting factors, prospects and recommendations

Heavy metals, dyes and pharmaceutical pollutants in water environment are considered as serious threat to the human and animal health globally. Rapid development of industrialization and agricultural activities are the major source for eliminating the toxic pollutants into the aquatic environment. Several conventional treatment methods have been suggested for the removal of emerging contaminants from wastewater. Algal biosorption, among other strategies and techniques, is demonstrating to be a limited technical remedy that is more focused and inherently more efficient and helps remove dangerous contaminants from water sources. The different environmental effects of harmful contaminants, including heavy metals, dyes, and pharmaceutical chemicals, as well as their sources, were briefly compiled in the current review. This paper provides a comprehensive definition of the future possibilities in heavy compound decomposition by using algal technology, from aggregation to numerous biosorption procedures. Functionalized materials produced from algal sources were clearly proposed. This review further highlights the limiting factors of algal biosorption to eliminate the hazardous material. Finally, this study showed how the existence of algae indicates a potential, effective, affordable, and sustainable sorbent biomaterial for minimizing environmental pollution.

Surface modified Acacia Senegal Gum based spherical hydrogel; fabrication, characterization, and kinetically optimized waste water treatment with remarkable adsorption efficiency

Acacia Senegal Gum hydrogel (HASG) with swollen dimension less than 50 μm were fabricated, and chemically modified with versatile diethylenetriamine (d-amine) to tailor the surface properties for environmental remediation. Negatively charged metal ions, for example, chromate (Cr(III)), dichromate (Cr(VI)), and arsenate (As(V)) were removed from aqueous media by using modified hydrogels (m-HASG). The FT-IR spectra revealed some new peaks due to d-amine treatment. The zeta potential measurements confirm a positively charged surface of HASG upon d-amine modification at ambient conditions. The absorption studies revealed that 0.05 g feed of m-(HASG) possesses 69.8, 99.3, and 40.00% cleaning potential against As(V), Cr(VI), and Cr(III), respectively with 2 h contact time in deionized water. Almost comparable adsorption efficiency was achieved by the prepared hydrogels towards the targeted analytes dissolved in real water samples. Adsorption isotherms, for example, Langmuir, Freundlich and modified Freundlich isotherms were applied to the collected data. Briefly, Modified Freundlich isotherm manifested comparatively agreeable line for the all adsorbents pollutants with highest R² figure. In addition, maximum adsorption capacity (Qm) with 217, 256, and 271 mg g^-1 numerical values were obtained against As(V), Cr(VI), and Cr(III), respectively. In real water samples, 217, 256, and 271 mg g^-1 adsorption capacity was represented by m-(HASG). In brief, m-(HASG) is a brilliant material for environmental application as cleaner candidate towards toxic metal ions.

A sustainable vanadium bioremediation strategy from aqueous media by two potential green microalgae

Globally, environmental concerns are rapidly growing due to increasing pollution levels. Vanadium is a hazardous heavy metal that poses health issues with an exposure concentration of about 2 ppm. It is regularly discharged by some industries and poses an environmental challenge. There are no sustainable green treatment methods for discharged effluents to mitigate vanadium threats to humans and the environment. In this study, the goal was to develop a green, sustainable method for removing vanadium and to utilize the produced biomass for biofuels, thus offsetting the treatment cost. Microalgae Chlorella sorokiniana SU1 and Picochlorum oklahomensis were employed for vanadium (III) treatment. The maximum removal was 25.5 mg L^-1 with biomass and lipid yields of 3.0 g L^-1 and 884.4 mg L^-1 respectively after 14 days of treatment. The vanadium removal capacity by microalgae was further enhanced up to 2-2.7 folds while optimizing the key parameters, pH, and temperature before removing biomass from the liquid phase. FTIR is used to analyse the reactive groups in algal cell walls to confirm vanadium adsorption and to understand the dominant and quantitative interactions. Zeta potential analysis helps to find out the most suitable pH range to facilitate the ionic bonding of biomass and thus maximum vanadium adsorption. This study addresses regulating external factors for enhancing the removal performance during microalgal biomass harvesting, which significantly enhances the removal of vanadium (III) from the aqueous phase. This strategy aims to improve the removal efficiency of microalgal treatment at an industrial scale for the bioremediation of vanadium and other inorganic pollutants.

A magnetic MIL-125-NH2@chitosan composite as a separable adsorbent for the removal of Cr(VI) from wastewater

Metal-organic frameworks (MOFs) are gradually used since of their huge specific surface area and superior pore structure. However, there are problems such as easy aggregation and difficult separation in water treatment. In this study, we prepared composite microspheres (FMCS-1) by modifying MIL-125-NH₂ with Fe₃O₄ and chitosan. The structural characterization and performance analysis of the materials showed that the introduction of chitosan effectively prevents the stacking of MOFs. The magnetic test manifested that Fe₃O₄ solved the problem of the difficult separation of MOFs from water. The removal potential of toxic Cr(VI) was tested by adsorption experiments. The isotherm model indicated that FMCS-1 is a single molecular layer adsorbent with a maximum adsorption capacity of 109.46 mg/g at pH = 2. The adsorption kinetics showed that the adsorption of Cr(VI) by FMCS-1 was chemical adsorption. The acid resistance test demonstrated that FMCS-1 can exist stably in acid solutions. The recycling experiments proved that the adsorbent can be reused and the removal percentage still reaches 50 % after 5 cycles. This work expands the application of MOFs in water treatment and also provides an effective adsorbent for Cr(VI) removal.