Biogenic glutamic acid-based resin: Its synthesis and application in the removal of cobalt(II)

Ultrasonic-assisted synthesis of lignin-based ultrasmall silver nanoparticles for photothermal-mediated sterilization

Lignin-based silver nanoparticles have been considered a promising antimicrobial material. However, it remains challenging to prepare ultra-small size silver nanoparticles sustainably with superior antibacterial performance. In this work, we modified ethanol-extracted lignin (EL) with carboxymethyl groups and further synthesized ultra-small particle size (3.8 ± 0.1 nm) nanosilver incorporated carboxymethyl lignin complexes (AgNPs@CEL) using ultrasonic technology. Due to the outstanding antibacterial properties of the ultra-small size nanosilver, AgNPs@CEL could cause 5.3 and 5.4 log10 CFU/mL reduction against E. coli and S. aureus in 5 min. Meanwhile, AgNPs@CEL exhibited remarkable photothermal antibacterial performance, which caused 6.2 and 6.1 log10 CFU/mL reduction of E. coli and S. aureus, with NIR irradiation for 5 min. Furthermore, the composite films prepared by doping only 0.5 wt% AgNPs@CEL into ethyl cellose could achieve a bactericidal rate more than 99.99 %. This study provides a new insight into design of controlled particle size lignin-based antibacterial nanosilver materials in a sustainable manner and holds promise for applications in antibacterial fields.

Statistical evaluation of liquid phase sequestration of acridine orange and Cr6+ by novel mesoporous glutamic acid-g-polyacrylamide/plaster of paris/riboflavin hydrogel nanocomposite

The adsorption of acridine orange and Cr⁶⁺ ion onto plaster of paris reinforced glutamic acid-grafted-polyacrylamide hydrogel nanocomposite modified with riboflavin, Glu-g-PAM/POP/Rb HNC was studied. The Glu-g-PAM/POP/Rb HNC was physico-chemically characterized by Fourier transform infrared spectroscopy, X-ray diffraction analysis, scanning electron microscopy coupled with energy dispersive X-ray spectroscopy, transmission electron microscopy and Brunauer-Emmett-Teller analysis. The specific surface area, pore volume and pore diameter were 15.48 m²/g, 0.015 cm³/g and 4.23 nm, respectively. Adsorption process was strategized by response surface methodology (RSM) based on a 3-level 5-factor (initial solution pH, contact time, adsorbent dose, initial adsorbate concentration and temperature) central composite design (CCD), and validity of the estimated parameters was statistically evaluated using analysis of variance (ANOVA). The optimized operating variables were: pH (AO = 10; Cr⁶⁺ = 4.15), contact time (AO = 60 min; Cr⁶⁺ = 59 min), adsorbent dose (0.8 g/L), initial adsorbate concentration (60 mg/L) and temperature (298 K). Isotherm results were coincident with Langmuir isotherm model. The experimental kinetic adsorption data was congruous with pseudo-second order model, with the uptake rate controlled by both intraparticle and liquid film diffusions. The relatively high Langmuir saturation capacity of 202.63 mg AO/g and 143.68 mg Cr⁶⁺/g, supported by the decent recyclability up to four times affirmed the promising performance of the adsorbent. The efficacy of the adsorbent for simultaneous removal of AO and Cr⁶⁺ from bi-component system was assessed. The possible adsorption mechanism mainly involved hydrogen bonding, van der Waals forces, electrostatic and π-π interactions. Adsorption of AO and Cr⁶⁺ onto Glu-g-PAM/POP/Rb HNC was feasible and exothermic as revealed by the thermodynamic parameters. The findings demonstrated superior adsorbent efficacy for the seizure of pollutants, particularly AO and Cr⁶⁺ from aqueous solution.

Sulfur-containing polymers derived from SO2: synthesis, properties, and applications

Sulfur-containing polymers enjoy the merits of excellent optical performance, degradation, chemical recyclability, and adhesive abilities toward metal ions. Recently, increasing attentions in both academic and industrial circles have been paid...

Water treatment using stimuli-responsive polymers

Stimuli-responsive polymers are a new category of smart materials used in water treatment via a stimuli-induced purification process and subsequent regeneration processes.

Preparation of graphene oxide-modified palygorskite nanocomposites for high-efficient removal of Co(II) from wastewater

Removing Co(II) from wastewater is urgent due to the threat to the environment and human health. In the work, the nanocomposite of graphene oxide-modified palygorskite (mPal-GO) is synthesized by cross-linking one-dimensional palygorskite (Pal) with two-dimensional material graphene oxide (GO), and used to remove Co(II) from wastewater. Its structure is characterized by Fourier transformed infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) surface area measurement. The parameters, such as mass ratio (GO:mPal), temperature, pH, and contact time, are carefully investigated. The results indicate that pseudo-second-order equation and Langmuir isotherm model are the best fitting one in the adsorption process of Co(II) onto mPal-GO. The maximum adsorption capacity achieves 16.9 mg/g at pH = 6.0 and T = 298 K according to the Langmuir model analysis. Furthermore, mPal-GO can be reused more than 5 times with a slight decrease according to the adsorption-desorption cycle experiments. Finally, mPal-GO with the low-cost and easy separation is a promising candidate for removing of Co(II) from wastewater.

Pertraction of Co(II) through Novel Ultrasound Prepared Supported Liquid Membranes Containing D2EHPA. Optimization and Transport Parameters

Pertraction of Co(II) through novel supported liquid membranes prepared by ultrasound, using bis-2-ethylhexyl phosphoric acid as carrier, sulfuric acid as stripping agent and a counter-transport mechanism, is studied in this paper. Supported liquid membrane characterization through scanning electron microscopy, energy-dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy shows the impregnation of the microporous polymer support by the membrane phase by the action of ultrasound. The effect on the initial flux of Co(II) of different experimental conditions is analyzed to optimize the transport process. At these optimal experimental conditions (feed phase pH 6, 0.5 M sulfuric acid in product phase, carrier concentration 0.65 M in membrane phase and stirring speed of 300 rpm in both phases) supported liquid membrane shows great stability. From the relation between the inverse of Co(II) initial permeability and the inverse of the square of carrier concentration in the membrane phase, in the optimized experimental conditions, the transport resistance due to diffusion through both the aqueous feed boundary layer (3.7576 × 10⁴ s·m⁻¹) and the membrane phase (1.1434 × 10¹⁰ s·m⁻¹), the thickness of the aqueous feed boundary layer (4.0206 × 10⁻⁶ m) and the diffusion coefficient of the Co(II)-carrier in the bulk membrane (4.0490 × 10⁻¹⁴ m²·s⁻¹), have been determined.

Cobalt enrichment enhances the tolerance of Botryococcus braunii to high concentration of CO2

This work mainly studied B. braunii adapted to different CO₂ concentrations with cobalt enrichment, and developed a process for CO₂ capture, hydrocarbon production and cobalt removal. The results showed that B. braunii favored rapid growth at 5.0% (v/v) CO₂, and the highest biomass was 1.89 g.L^-1 with 4.5 mg.L^-1 of cobalt. Hydrocarbon productivity in high concentration CO₂ (5.0% and 10.0%) with cobalt enrichment was higher than that in Chu 13 medium. The change in cobalt removal efficiency mainly corresponded to the growth of B. braunii. The LCE of B. braunii in cobalt-rich with high CO₂ concentration (5.0% and 10.0%) was 15.7%, and 14.9%, respectively, which was higher than that in normal medium. CO₂ fixation rates were also higher in cobalt enrichment coupled with high CO₂ concentration. This study not only provides ideas for the removal of toxic metal cobalt, but also has great potential for CO₂ biofixation.

Electro-enhanced removal of cobalt ions from aqueous solution by capacitive deionization

Electro-enhanced removal of cobalt (Co) ions from aqueous solution by capacitive deionization (CDI) was investigated in this study. The effect of applied voltage and initial Co ions concentration, as well as coexisted ions on removal efficiency of Co ions was determined. Co ions adsorption performance was also evaluated by kinetic models, isotherm models and three mass transfer models. The results indicated that the removal efficiency of Co ions had positive correlation with applied voltage (R² = 0.9991), which increased from 15.11% to 36.54% when the applied voltage increased from 0 V to 1.2 V. However, the removal efficiency of Co ions decreased gradually from 36.54% to 9.51% with the increasing initial Co ions concentration from 5 to 30 mg L^-1. The coexisted ions (Sr and Cs) also largely inhibited the removal efficiency of Co ions and make it reduce to 8.37%. After fitting the adsorption data, pseudo-second order (PSO) model was better than pseudo-first order (PFO) for each applied voltage and initial concentration. A monolayer adsorption is the main adsorption mechanism of Co ions adsorption on the activated carbon cloth (ACC) because of the higher regression coefficient (0.964) by Langmuir isotherm. Based on kinetics together with the equilibrium isotherm, three mass transfer models were established and adsorption of the ions onto the active sites (AAS) model is the rate-limiting step due to the best fitting for the kinetic adsorption data of Co ions on ACC electrode. In addition, the Co ions were uniformly distributed on ACC electrode after adsorption.

Comparative transcriptome analyses of oleaginous Botryococcus braunii race A reveal significant differences in gene expression upon cobalt enrichment

BACKGROUND

Botryococcus braunii is known for its high hydrocarbon content, thus making it a strong candidate feedstock for biofuel production. Previous study has revealed that a high cobalt concentration can promote hydrocarbon synthesis and it has little effect on growth of B. braunii cells. However, mechanisms beyond the cobalt enrichment remain unknown. This study seeks to explore the physiological and transcriptional response and the metabolic pathways involved in cobalt-induced hydrocarbon synthesis in algae cells.

RESULTS

Growth curves were similar at either normal or high cobalt concentration (4.5 mg/L), suggesting the absence of obvious deleterious effects on growth introduced by cobalt. Photosynthesis indicators (decline in Fv/Fm ratio and chlorophyll content) and reactive oxygen species parameters revealed an increase in physiological stress in the high cobalt concentration. Moreover, cobalt enrichment treatment resulted in higher crude hydrocarbon content (51.3% on day 8) compared with the control (43.4% on day 8) throughout the experiment (with 18.2% improvement finally). Through the de novo assembly and functional annotation of the B. braunii race A SAG 807-1 transcriptome, we retrieved 196,276 non-redundant unigenes with an average length of 1086 bp. Of the assembled unigenes, 89,654 (45.7%), 42,209 (21.5%), and 32,318 (16.5%) were found to be associated with at least one KOG, GO, or KEGG ortholog function. In the early treatment (day 2), the most strongly upregulated genes were those involved in the fatty acid biosynthesis and metabolism and oxidative phosphorylation, whereas the most downregulated genes were those involved in carbohydrate metabolism and photosynthesis. Genes that produce terpenoid liquid hydrocarbons were also well identified and annotated, and 21 (or 29.2%) were differentially expressed along the cobalt treatment.

CONCLUSIONS

Botryococcus braunii SAG 807-1 can tolerate high cobalt concentration and benefit from hydrocarbon accumulation. The time-course expression profiles for fatty acid biosynthesis, metabolism, and TAG assembly were obtained through different approaches but had equally satisfactory results with the redirection of free long-chain fatty acid and VLCFA away from TAG assembly and oxidation. These molecules served as precursors and backbone supply for the fatty acid-derived hydrocarbon accumulation. These findings provide a foundation for exploiting the regulation mechanisms in B. braunii race A for improved photosynthetic production of hydrocarbons.

Poly (γ-Glutamic Acid) Promotes Enhanced Dechlorination of p-Chlorophenol by Fe-Pd Nanoparticles

Nanoscale zero-valent iron (nZVI) has shown considerable promise in the treatment of chlorinated organic compounds, but rapid aggregation and inactivation hinder its application. In this study, palladium-doped zero-valent iron nanoparticles involving poly (γ-glutamic acid) (Fe-Pd@PGA NPs) were synthesized. The nanoparticles were small (~100 nm), uniformly distributed, and highly stable. The dechlorination performance of Fe-Pd@PGA NPs was evaluated using p-CP as a model. The results demonstrated that Fe-Pd@PGA NPs show high activity even in weakly alkaline conditions. The maximum rate constant reached 0.331 min^- 1 at pH 9.0 with a Fe to p-CP ratio of 100. Additionally, the dechlorination activity of Fe-Pd@PGA NPs is more than ten times higher than that of the bare Fe-Pd NPs, demonstrating the crucial role of PGA in this system. Furthermore, we investigated the dechlorination performance in the presence of different anions. The results indicated that Fe-Pd@PGA NPs can maintain high activity in the presence of Cl^-, H₂PO₄^-, and humic acid, while HPO₄^2-and HCO₃^- ions slightly reduce the dechlorination activity. We believed that PGA is a promising stabilizer and promoter for Fe-Pd NPs and the Fe-Pd@PGA NPs have the potential for practical applications.