Bioproduction, purification, partial characterization and phenol removal efficacy of tyrosinase enzyme from Streptomyces sp. strain MR28.

The study focused on the production of the tyrosinase enzyme from Streptomyces sp. MR28 and its potency in removal of phenol content from water using free and immobilized tyrosinase enzyme. The tyrosinase was produced by Streptomyces sp. MR28 in liquid tyrosine broth medium, and it was further purified to near its homogeneity by employing, precipitation, dialysis, and column chromatography. After the purification, 44.49% yield with a 4 fold purification was achieved. The characterization of the purified enzyme showed a single major peak on HPLC and a solitary band on SDS-PAGE. The purified tyrosinase enzyme was active at a pH of 7.0 and a temperature of 30 °C. Further immobilization of purified tyrosinase was performed using the sodium alginate entrapment method. The capacity of the purified tyrosinase to remove phenol in water was evaluated by spectrophotometric method. The free tyrosinase enzyme-treated solutions showed a gradual decrease in the concentration of phenol with increased incubation time at 30 °C and 40 °C, at 90 min of the incubation time, it showed maximum efficacy in removing phenol from the solution. At 50 °C and 60 °C, the free tyrosinase enzyme exhibited very less capacity to remove the phenol. The immobilized enzyme showed good capacity for the removal of phenol from the solutions; the concentration of phenol in the solution decreased with an increase in the incubation time. At temperatures of 40 °C and 50 °C, the immobilized tyrosinase enzyme beads showed significant removal of phenol from the solution, and at temperatures of 30 °C and 60 °C, they also exhibited good capacity for the removal of phenol. At the end of the 90 min incubation period, it exhibited good capability. The current study suggests using immobilized microbial tyrosinase enzyme can be used for the removal of phenol from the contaminated water in a greener manner.

The mechanism of survival and degradation of phenol by Acinetobacter pittii in an extremely acidic environment.

The treatment efficiency of acidic phenol-containing wastewater is hindered by the absence of efficient acid-resistant phenol-degrading bacteria, and the acid-resistant mechanism of such bacteria remains poorly studied. In this study, the acid-resistant strain Hly3 was used as a research model to investigate its ability to degrade phenol and its underlying mechanism of acid resistance. Strain Hly3 exhibited robust acid resistance, capable of surviving in extremely acidic environments (pH 3) and degrading 1700 mg L-1 phenol in 72 h. Through the physiological response analysis of strain Hly3 to pH, the results indicated: firstly, the strain could reduce the relative permeability of the cell membrane and increase EPS secretion to prevent H+ from entering the cell (shielding effect); secondly, the strain could accumulate more buffering substances to neutralize the intracellular H+ (neutralization effect); thirdly, the strain could expel H+ from the cell by enhancing H+-ATPase activity (pumping effect); finally, the strain produced more active scavengers to reduce the toxicity of acid stress on cells (antioxidant effect). Subsequently, combining liquid chromatography-mass spectrometry (LC-MS) technology with exogenous addition experiments, it was verified that the acid resistance mechanism of microorganisms is achieved through the activation of acid-resistant response systems by glutamine, thereby enhancing functions such as shielding, neutralization, efflux, and antioxidation. This study elucidated the acid resistance mechanism of Acinetobacter pittii, providing a theoretical basis and guidance for the treatment of acidic phenol-containing wastewater.

Elucidated potential of immobilized Janibacter sp. for saline wastewater phenol removal.

Phenolic compounds are commonly found in industrial effluents and can be hazardous to organisms even at low concentrations. Over the years, researchers have demonstrated that bioremediation is a cost-effective and environmentally friendly alternative to physicochemical approaches used to remove phenol. The aim of this study was to investigate the removal of phenol from saline wastewaters by a halotolerant strain of the genus Janibacter. For this purpose, bacterial cells were immobilized on different supports, from which mica and zeolite were ultimately chosen due to their higher removal efficiency. The wet weight of immobilized cells per 1 g of mica and zeolite was 0.51 and 0.48 g, respectively. Free cells consumed 100 mg/L of phenol in 88 h, while immobilized cells used it in 40 h. Immobilized cells revealed a higher thermostability and could operate over a wider pH range and salinity. Unlike free cells, immobilized cells could remove 700 mg/L of phenol and could be reused for at least nine cycles. Interestingly the phenol removal efficiency of zeolite-immobilized cells remained unchanged after 4 months of storage at 4 and - 20 °C, which could be of great advantage for industrial applications. Complete destruction of phenol was observed through the meta pathway comprising phenol hydroxylase and catechol 2,3-dioxygenase enzymes. KEY POINTS: • Mica- and zeolite-immobilized cells were able to consume high concentrations of phenol. • Cells immobilized on mica and zeolite had considerable operational and storage stability. • Immobilized cells could be a good candidate for phenol removal in saline environments.

Degradation of phenol using Fe(II)-activated CaO2: effect of ball-milled activated carbon (ACBM) addition.

In-situ chemical oxidation (ISCO) based on peroxide activation is one of the most promising technologies for removing organic contaminants from natural groundwater (NGW). However, use of the most common form of hydrogen peroxide (H2O2) is limited owing to its significantly rapid reaction rate and heat generation. Therefore, in the present study, the activation of calcium peroxide (CaO2), a slow H2O2 releasing agent, by Fe(II) was proposed (CaO2/Fe(II)), and the phenol degradation mechanisms and feasibility of NGW remediation were investigated. The optimum molar ratio of [phenol]/[CaO2]/[Fe(II)] (phenol = 0.5 mM) was 1/10/10, resulting in 87.0-92.5% phenol removal within 120 min under a broad initial pH range of 3-9. HCO3-, PO43-, and humic acid significantly inhibited degradation, whereas the effects of Cl-, NO3-, and SO42- were negligible. Reactive oxygen species (ROS) were identified based on the results of phenol degradation in the presence of scavengers and electron spin resonance (ESR) spectroscopy, which demonstrated that 1O2 played the dominant role, supported by •OH, in CaO2/Fe(II). Phenol removal in NGW (67.81%) was less than that in distilled and deionized water (DIW, 92.5%) at a [phenol]/[CaO2]/[Fe(II)] ratio of 1/10/10. However, phenol removal was significantly improved (∼100%) by increasing the CaO2 and Fe(II) doses to 1/20/20-40. Furthermore, when 125-250 mg L-1 of ball-milled activated carbon (ACBM) was added (CaO2/Fe(II)-ACBM), phenol removal was enhanced from 67.81% to 90.94-100% in the NGW. CaO2/Fe(II)-ACBM exhibited higher total organic carbon (TOC) removal than CaO2/Fe(II). In addition, no notable by-products were detected using CaO2/Fe(II)-ACBM, whereas the polymerisation products of hydroxylated and/or ring-cleaved compounds, that is, aconitic acid, gallocatechin, and 10-hydroxyaloin, were found in the reaction with CaO2/Fe(II). These results strongly suggest that CaO2/Fe(II)-ACBM is highly promising for groundwater remediation, minimizing degradation byproducts and the adverse effects caused by the NGW components.

A novel bioprocess combining anaerobic co-digestion followed by ultra-filtration and microalgae culture for optimal olive mill wastewater treatment.

Treatment of olive mill wastewater (OMW) has received considerable research globally due to its influence on the technical, economic, and environmental sustainability of wastewater biogas production. This work presents a novel combined biological process for OMW treatment in terms to produce for the first time, treated OMW and a valuable microalgae biomass. The process involves anaerobic co-digestion (AD), a low cut-off membrane ultra-filtration (UF) and a subsequent Scenedesmus sp. culture. The AD of OMW was conducted at high initial COD ranging from 28 to 38 g/L using an up-flow anaerobic fixed bed bio-reactor (300 L). Results revealed that the maximum biogas production was about 0.507 L/g CODintroduced.day containing 73% of methane corresponding to a methane yield of 0.370 L/g CODintroduced.day obtained at an organic loading rate of 4.58 g COD/L.day. High removal levels of COD, total phenolic compounds, and total suspended solids in the anaerobic liquid digestate (ALD) were achieved after AD and UF. Scenedesmus sp. was then cultivated on the ultra-filtrated ALD. A maximum biomass productivity of 0.15 g/L.day was recorded when Scenedesmus sp. is grown on 25% of ultra-filtrated ALD with a maximum nitrogen removal rate of 15.18 mg/L.day and an almost total elimination of phosphorus and phenolic compounds.

The effect of pre-treatment methods on membrane flux, COD, and total phenol removal efficiencies for membrane treatment of pistachio wastewater.

In this study, the effect of pre-treatment methods was investigated for membrane treatment of pistachio processing wastewater (PPW). Chemical coagulation, electrocoagulation, and electrooxidation processes were tested as the pretreatment methods to understand the effect of pretreatment on membrane performance. Alum (Al2(SO4)3·18H2O), iron (III) chloride (FeCl3·6H2O) and iron(II) sulfate (Fe(SO4)·7H2O) were used as coagulant and anionic polyelectrolyte was used as flocculant. Al-Al and Fe-Fe electrode pairs were used in the electrocoagulation experiments while platinum (Pt), boron doped diamond (BDD), and graphite were used in the electrooxidation experiments. UP150, NF270, and NF90 were used as the membranes. Chemical oxygen demand (COD) and total phenol removal efficiencies from wastewater were determined by considering membrane flux. For chemical coagulation experiments, the highest COD removal efficiency was determined as 44.9% for Al2(SO4)3.18H2O at 1000 mg/L when the wastewater pH value was 8.0. However, the highest total phenol removal efficiencies were obtined as 62.5% at 4000 mg/L for FeCl3.6H2O at pH 8. For electrocoagulation experiments, the highest COD and total phenol removal efficiencies were determined as 63.9% at pH 4.0 and 74.2% at pH 7.0, respectively, for 100 A/m2 current density when aluminum electrode pairs were used. For electrooxidation experiments, the highest COD and total phenol removal efficiencies were determined as 61.2% at pH 4.0 and 83.1% at pH 10, respectively, for 200 A/m2 current density when BDD-Pt electrode pairs were used. Raw PPW and pre-treated PPW with chemical coagulation, electrocoagulation, and electrooxidation processes were progressively further treated with ultrafiltration (UP150) and nanofiltration (NF270, NF90) membranes to improve COD and total phenol removal efficiencies. The results showed that the permeate of NF90 membrane supplied the highest COD (96.0%) and total phenol removal (97.5%) efficiencies for the raw wastewater. However, COD and total phenol removal efficiencies were determined as 98.6% and 100% for electrocoagulation + NF90, 97.9% and 100% for electrooxidation + NF90, 96.6% and 100% for chemical coagulation + NF90, respectively. The steady-state fluxes for NF90 membranes were 2.9, 7.0, and 8.6 L/m2h after chemical coagulation, electrooxidation, and electrocoagulation, respectively. The results depicted that electrocoagulation and electrooxidation were the most suitable pre-treatment methods for water recovery using NF90 membrane.

Engineered bacterial biofloc formation enhancing phenol removal and cell tolerance.

A microbial floc consisting of a community of microbes embedded in extracellular polymeric substances matrix can provide microbial resistances to toxic chemicals and harsh environments. Phenol is a toxic environmental pollutant and a typical lignin-derived phenolic inhibitor. In this study, we genetically engineered Escherichia coli cells by expressions of diguanylate cyclases (DGCs) to promote proteinaceous and aliphatic biofloc formation. Compared with the planktonic E. coli cells, the biofloc-forming cells improved phenol removal rate by up to 2.2-folds, due to their substantially improved tolerance (up to 149%) to phenol and slightly enhanced cellular activity (20%) of phenol hydroxylase (PheH). The engineered bioflocs also improved E. coli tolerance to other toxic compounds such as furfural, 5-hydroxymethylfurfural, and guaiacol. Additionally, the strategy of the engineered biofloc formation was applicable to Pseudomonas putida and enhanced its tolerance to phenol. This study highlights a strategy to form engineered bioflocs for improved cell tolerance and removal of toxic compounds, enabling their universality of use in bioproduction and bioremediation.

Immobilization of horseradish peroxidase on electrospun magnetic nanofibers for phenol removal.

In this study, Fe3O4/polyacrylonitrile (PAN) magnetic nanofibers (MNFs) were fabricated by electrospinning method to immobilize the horseradish peroxidase (HRP), making which a complex platform for phenol removal application. Results indicated that, the average diameter of MNFs was about 200-400 nm and the maximum saturation magnetic induction was 19.03 emu/g. Compared with the free HRP, the modified HRP showed no change in optimum pH, but showed higher catalytic activity. Moreover, HRP immobilized MNFs (H-MNFs) with 40% Fe3O4 nanoparticles loading had the lowest HRP loading, but had the highest relative activity, because of the magnetic synergy with the presence of MNPs. Subsequently, the 40% H-MNFs was used for the remediation of phenol wastewater, achieved the removal efficiency of phenol to 85% in the first round use, and remained 52% of efficiency after 5 recycles using. It was expected that the H-MNFs could be a potential application in wastewater treatment such as phenol removal.

Growth behavior, glucose consumption and phenol removal efficiency of Chlorella vulgaris under the synergistic effects of glucose and phenol.

The use of algae is an effective approach to remove phenol and its derivatives from polluted water. The growth behavior, glucose consumption and phenol removal efficiency of Chlorella vulgaris under the synergistic effects of glucose and phenol were investigated. The evolutions of tolerance and removal efficiency of C. vulgaris to phenol under different trophic modes and glucose contents were observed. The results revealed that growth of C. vulgaris were inhibited with the increase of phenol from 0 to 400 mg L-1 in culture media; the tolerance to phenol enhanced with the addition of glucose from 2 to 10 g L-1, while glucose consumption was inhibited with the increase of phenol content; phenol removal efficiency varied with glucose concentrations in mixotrophic media. The finding suggested that phenol inhibited the growth of C. vulgaris and glucose assimilation under mixotrophic cultivation, while appropriate glucose addition could enhance the tolerance of C. vulgaris to phenol and affect the phenol removal efficiency.

Phenol removal by laccases and other phenol oxidases of Pleurotus sajor-caju PS-2001 in submerged cultivations and aqueous mixtures.

In this work, phenol removal from aqueous solutions by Pleurotus sajor-caju PS-2001 phenol oxidases was assessed under different conditions. In stirred-tank reactor (STR), 77, 82, 92 and 36% of removal were attained when initial concentrations of 1.0, 2.0, 3.0 and 4.0 mmol L-1 phenol, respectively, were used. Among the different enzymes produced by this fungus, phenol removal seems to be related to the activity of laccases that attained maximum values between 33 and 91 U mL-1 in STR. With an internal-loop airlift reactor (ILAR), phenol concentrations of 1.0, 2.0, 3.0, 4.0 and 5.0 mmol L-1 were evaluated, and removal of 70, 76, 82, 77 and 82%, respectively, were observed. In ILAR, however, superior maximum titres of laccases were quantified (80-285 U mL-1). Crude enzyme broths have also been tested for phenol removal from 3.0 mmol L-1 aqueous solutions, the best result (55% of removal) being obtained at pH 3.2 and 30 °C, without agitation, using 60 U mL-1 laccases. According to the data presented, phenol can be efficiently removed from liquid media in submerged cultures of P. sajor-caju PS-2001 even when carried out in a simple pneumatic reactor, whereas significantly less amount of the pollutant is degraded when a crude enzyme broth is used.

Simple screening protocol for identification of potential mycoremediation tools for the elimination of polycyclic aromatic hydrocarbons and phenols from hyperalkalophile industrial effluents.

A number of fungal strains belonging to the ascomycota, basidiomycota and zygomycota genera were subjected to an in vitro screening regime to assess their ligninolytic activity potential, with a view to their potential use in mycoremediation-based strategies to remove phenolic compounds and polycyclic aromatic hydrocarbons (PAHs) from industrial wastewaters. All six basidiomycetes completely decolorized remazol brilliant blue R (RBBR), while also testing positive in both the guaiacol and gallic acid tests indicating good levels of lignolytic activity. All the fungi were capable of tolerating phenanthrene, benzo-α- pyrene, phenol and p-chlorophenol in agar medium at levels of 10 ppm. Six of the fungal strains, Pseudogymnoascus sp., Aspergillus caesiellus, Trametes hirsuta IBB 450, Phanerochate chrysosporium ATCC 787, Pleurotus ostreatus MTCC 1804 and Cadophora sp. produced both laccase and Mn peroxidase activity in the ranges of 200-560 U/L and 6-152 U/L, respectively, in liquid media under nitrogen limiting conditions. The levels of adsorption of the phenolic and PAHs were negligible with 99% biodegradation being observed in the case of benzo-α-pyrene, phenol and p-chlorophenol. The aforementioned six fungal strains were also found to be able to effectively treat highly alkaline industrial wastewater (pH 12.4). When this wastewater was supplemented with 0.1 mM glucose, all of the tested fungi, apart from A. caesiellus, displayed the capacity to remove both the phenolic and PAH compounds. Based on their biodegradative capacity we found T. hirsuta IBB 450 and Pseudogymnoascus sp., to have the greatest potential for further use in mycoremediation based strategies to treat wastestreams containing phenolics and PAHs.

Reduction in toxicity of coking wastewater to aquatic organisms by vertical tubular biological reactor.

We conducted a battery of toxicity tests using photo bacterium, algae, crustacean and fish to evaluate acute toxicity profile of coking wastewater, and to evaluate the performance of a novel wastewater treatment process, vertical tubular biological reactor (VTBR), in the removal of toxicity and certain chemical pollutants. A laboratory scale VTBR system was set up to treat industrial coking wastewater, and investigated both chemicals removal efficiency and acute bio-toxicity to aquatic organisms. The results showed that chemical oxygen demand (COD) and phenol reductions by VTBR were approximately 93% and 100%, respectively. VTBR also reduced the acute toxicity of coking wastewater significantly: Toxicity Unit (TU) decreased from 21.2 to 0.4 for Photobacterium phosphoreum, from 9.5 to 0.6 for Isochrysis galbana, from 31.9 to 1.3 for Daphnia magna, and from 30.0 to nearly 0 for Danio rerio. VTBR is an efficient treatment method for the removal of chemical pollutants and acute bio-toxicity from coking wastewater.

Hierarchical hybrid peroxidase catalysts for remediation of phenol wastewater.

We report a new family of hierarchical hybrid catalysts comprised of horseradish peroxidase (HRP)-magnetic nanoparticles for advanced oxidation processes and demonstrate their utility in the removal of phenol from water. The immobilized HRP catalyzes the oxidation of phenols in the presence of H2 O2 , producing free radicals. The phenoxy radicals react with each other in a non-enzymatic process to form polymers, which can be removed by precipitation with salts or condensation. The hybrid peroxidase catalysts exhibit three times higher activity than free HRP and are able to remove three times more phenol from water compared to free HRP under similar conditions. In addition, the hybrid catalysts reduce substrate inhibition and limit inactivation from reaction products, which are common problems with free or conventionally immobilized enzymes. Reusability is improved when the HRP-magnetic nanoparticle hybrids are supported on micron-scale magnetic particles, and can be retained with a specially designed magnetically driven reactor. The performance of the hybrid catalysts makes them attractive for several industrial and environmental applications and their development might pave the way for practical applications by eliminating most of the limitations that have prevented the use of free or conventionally immobilized enzymes.

Phenol removal from refinery wastewater by mutant recombinant horseradish peroxidase.

Application of mutated recombinant horseradish peroxidase (HRP) for phenol removal from refinery effluents is reported. Recombinant HRP produced in Escherichia coli suffers from the disadvantage of lacking glycosylation, which affects its catalytic efficiency and stability toward inactivating parameters such as increased temperature and enhanced amounts of hydrogen peroxide. In the present study, the previously reported variant (in which Asn268 was substituted with Asp, N268D) with improved stability characteristics and catalytic efficiency was used to remove phenol from a petroleum refinery effluent. The presence and removal of phenol was studied by high-performance liquid chromatography; the precipitated oxidized phenol was also observed and removed from the sample by centrifugation. Results showed that the N268D variant can remove 61%, 67%, and 81% of phenol from effluent in 1, 2, and 16 H, respectively. By exploiting the N268D mutant, removal of 50% phenol could be achieved in 42 Min, which was more than 22 times less than the treatment time required by native recombinant enzyme.

Preparation of Mn-doped sludge biochar and its catalytic activity to persulfate for phenol removal.

In recent years, the increasing prevalence of phenolic pollutants emitted into the environment has posed severe hazards to ecosystems and living organisms. Consequently, there is an urgent need for a green and efficient method to address environmental pollution. This study utilized waste sludge as a precursor and employed a hydrothermal-calcination co-pyrolysis method to prepare manganese (Mn)-doped biochar composite material (Mn@SBC-HP). The material was used to activate peroxydisulfate (PDS) for the removal of phenol. The study investigated various factors (such as the type and amount of doping metal, pyrolysis temperature, catalyst dosage, PDS dosage, pH value, initial phenol concentration, inorganic anions, and salinity) affecting phenol removal and the mechanisms within the Mn@SBC-HP/PDS system. Results indicated that under optimal conditions, the Mn@SBC-HP/PDS system achieved 100% removal of 100 mg/L phenol within 180 min, with a TOC removal efficiency of 82.7%. Additionally, the phenol removal efficiency of the Mn@SBC-HP/PDS system remained above 90% over a wide pH range (3-9). Free radical quenching experiments and electron spin resonance (ESR) results suggested that hydroxyl radicals (·OH) and sulfate radicals (SO4-) yed a role in the removal of phenol through radical pathways, with singlet oxygen (1O2) being the dominant non-radical pathway. The phenol removal efficiency remained above 90%, demonstrating the excellent adaptability of the Mn@SBC-HP/PDS system under the interference of coexisting inorganic anions or increased salinity. This study proposes an innovative method for the resource utilization of waste, creating metal-biochar composite catalysts for the remediation of water environments. It provides a new approach for the efficiency of organic pollutants in water environments.

The effect of use of Ni/Fe and mZVI on phenol removal with the heterogenous fenton process and in-situ generation of H2O2.

To degrade phenol with the heterogeneous Fenton-like process and to compare the results, micro-scale zero-valent iron particles (mZVI) and nickel-coated iron bimetallic particles (Ni/Fe) were used. Oxygen was given to the system and converted to H2O2 and •OH radicals. The changes in the properties of mZVI and Ni/Fe particles after the reaction were determined by scanning electron microscope (SEM), X-ray energy-dispersive spectrometer (EDX), Brunauer-Emmett-Teller (BET), X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) before and after the reaction. For phenol removal with an initial phenol concentration of 25 mg/L, initial pH of 3 and air flow rate of 150 L/h, 3 g/L dosage and 360 min reaction time for mZVI, 1.5 g/L dosage and 240 min for Ni/Fe reaction time were sufficient. Under these conditions, 76% and 98% phenol removal and 39% and 47% total organic carbon (TOC) removal were obtained for mZVI and Ni/Fe, while 189 and 85 mg/L H2O2 were produced, respectively. While SO4-2 and PO4-3 caused a slight increase in phenol removal efficiency in the mZVI system, these ionic species and Cl- and NO3- caused a decrease in the efficiency in the Ni/Fe system. The possible degradation pathway for phenol was suggested by high performance liquid chromatography (HPLC) analysis and hydroquinone, pyrocatechol, maleic acid, benzoquinone and acetic acid were the main intermediates. According to the cost analysis, when using mZVI to treat 1 m3 25 mg/L phenolic wastewater, the cost was $228.15, which was 1.45 times higher than the cost for Ni/Fe.

Thermodynamic and kinetic analysis of the response surface method for phenol removal from aqueous solution using graphene oxide-polyacrylonitrile nanofiber mats.

Phenolic compound even at low concentrations, are considered to be priority pollutants due to their significant toxicity. Electrospinning was used to create a polyacrylonitril (PAN) nanofiber, which was then impregnated with graphene oxide (GO). After a preliminary investigation into the electrospinning parameters (e.g., using various voltages and polymer concentrations), the electrospun nanofibres were tuned, this study evaluated the effectiveness of these materials in removing phenolic compounds from wastewater through adsorption. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) were used to analyze the synthesized nanofiber mats. The scanning electron microscopy (SEM) analysis revealed that the structure of nanofiber mats was altered by the addition of graphene oxide (GO) in different ratios. Specifically, the surface of the fibres exhibited increased roughness, and the diameter of the fibres also experienced an increase. The average diameter of the fibres was measured to be (134.9 ± 21.43 nm) for the PAN/2.5% GO composite and (198 ± 33.94 nm) for the PAN/5% GO composite. FTIR spectra of the PAN/GO nanocomposites nanofiber displayed distinct peaks associated with graphene oxide (GO). These included a wide peak at 3400 cm-1, related to the presence of hydroxyl (O-H) groups, as well as peaks on 1600 as well as 1000 cm-1, which indicated the existence of epoxy groups. In this study response surface methodology (RSM) was implemented. To enhance the efficiency of removing substances, it is necessary to optimise parameters such as pH, contact time, and dosage of the adsorbent. The optimum pH for removing phenol via all nanofiber mats was determined to be 7, while at a dose of 2 mg dose adsorbents maximum removals for pure PAN, PAN/2.5 GO, and PAN/5 GO were 61.3941, 77.2118, and 92.76139%, respectively. All the adsorbents obey Langmuir isotherm model, and the empirical adsorption findings were fitted with the second-order model kinetically, also non-linear Elovich model. The maximal monolayer adsorption capacities for PAN, PAN/2.5 GO, and PAN/5 GO were found to be 57.4, 66.18, and 69.7 mg/g, respectively. Thermodynamic studies discovered that the adsorption of phenol on all adsorbents nanofiber mats was exothermic, the adsorption of phenol on nanofiber mats decreases as the temperature increases. All the adsorbents exhibit negative enthalpy and entropy. The PAN/GO composite's superior phenol removal suggested that it could be used as a latent adsorbent for efficient phenol removal from water and wastewater streams.

Bias-free glucose/O2 bio-photoelectrochemical system for multi-energy conversion and phenolic pollutant degradation.

Developing a multi-functional green energy device that propels sustainable energy development and concurrently purifies environmental pollutants offers an irresistibly compelling vision for a cleaner future. Herein, we reported a bias-free glucose/O2 bio-photoelectrochemical system (BPECS) for both energy conversion and phenolic pollutants degradation. Coupling a glucose dehydrogenase (GDH) modified self-assembled meso-tetrakis (4-carboxyphenyl)-porphyrin (SA-TCPP)-sensitized TiO2 biophotoanode for glucose oxidation and nitrogen/oxygen doped cobalt single-atom catalyst (CoNOC) cathode for two-electron oxygen reduction, both solar and biochemical energies were converted into electric power in BPECS with a maximum power density of 296.98 µW cm-2 (0.49 V). Working in synergy with horseradish peroxidase (HRP) biocatalysis, the cathode-generated H2O2, a by-product, is effectively redeployed for degrading phenol, attaining an impressive degradation efficiency of approximately 100% within 60 min. Additionally, aiming to scale up this ingenious BPECS approach, peroxidase-mimicking Co3O4 nanozyme were engineered as a substitute for natural HRP. Remarkably, these nanozyme demonstrated a comparable degradation efficiency, achieving the same result in 90 min. In this work, our results demonstrate that this bias-free glucose/O2 BPECS model marks a significant step forward in integrating renewable energy harvesting with environmental remediation, but also opens new avenues for the versatile application of nanozymes.

Enhanced photocatalytic decomposition of phenol in wastewater by using La-TiO2 nanocomposite.

In this work, La-TiO2 nanocomposite was synthesized by loading lanthanum onto TiO2 and used for improving photodegradation of phenol in wastewater. The characterizations of La-TiO2 demonstrated that the loading of La onto TiO2 not only increased its adsorption light zone up to 470 nm but also decreased the band gap energy from 3.1 to 2.64 eV. Photoluminescence spectra of La-TiO2 confirmed the enhancing separation rate between electron and hole, leading to improve photodegradation efficiency of phenol. The removal rate of phenol was influenced by solution pH and alkaline conditions could bring better removal efficiency. In presence of light, the photodegradation efficiency of phenol by TiO2 was 64.1%, while it increased up to 93.4% by La-TiO2 photocatalyst. La-TiO2 nanocomposite was tested for five cycles and it showed only 13.8% dropping in the photodegradation efficiency of phenol. Besides, over 82% of phenol was removed from the wastewater sample by modified TiO2, demonstrating the potential of La-TiO2 photocatalyst for water pollution control.

Sustainable removal of phenol from wastewater using a biopolymer hydrogel adsorbent comprising crosslinked chitosan and κ-carrageenan.

A biopolymer-based adsorbent comprising chitosan (CS) and κ-carrageenan (κ-Carr) was synthesised and evaluated to treat phenolic-contaminated water. The developed CS/κ-Carr hydrogel demonstrated excellent performance with a phenol adsorption uptake of 80 %. The morphologies of CS/κ-Carr hydrogels with different ratios of CS to κ-Carr ranging from 1:2 to 7:3 were characterised using scanning electron microscopy and atomic force microscopy; their chemical structures were investigated by spectral analyses using Fourier-transform infrared spectroscopy, thermogravimetric analysis, and differential scanning calorimetry; their adsorption characteristics were determined using tests for swelling, chemical stability, hygroscopic moisture content, and hydrophilicity. Finally, a batch-type evaluation method demonstrated adsorption performance at 25 °C and pH 6.9. Adsorption isotherms and kinetic data were successfully obtained using the Freundlich and pseudo-second-order models, respectively. The results indicate that one-pot synthesis of an insoluble CS/κ-Carr hydrogel adsorbent exhibits considerable potential for the removal of phenol from aqueous solutions, providing an environmentally friendly technology enhancing the phenol adsorption performance of CS.