Photocatalytic Optical Hollow Fiber with Enhanced Visible-light-driven CO2 Reduction.

A visible-light-driven CO2 reduction optical fiber is fabricated using graphene-like nitrogen-doped composites and hollow quartz optical fibers to achieve enhanced activity, selectivity, and light utilization for CO2 photoreduction. The composites are synthesized from a lead-based metal-organic framework (TMOF-10-NH2 ) and g-C3 N4 nanosheet (CNNS) via electrostatic self-assembly. The TMOF-10-NH2 /g-C3 N4 (TMOF/CNNS) photocatalyst with an S-type heterojunction is coated on optical fiber. The TMOF/CNNS coating, which has a bandgap energy of 2.15 eV, has good photoinduced capability at the coating interfaces, high photogenerated electron-hole pair yield, and high charge transfer rate. The conduction band potential of the TMOF/CNNS coating is more negative than that for CO2 reduction. Moreover, TMOF facilitates the CO desorption on its surface, thereby improving the selectivity for CO production. High CO2 photoreduction and selectivity for CO production is demonstrated by the TMOF/CNNS-coated optical fiber with the cladding/core diameter of 2000/1000 µm, 10 wt% TMOF in CNNS, coating thickness of 25 µm, initial CO2 concentration of 90 vol%, and relative humidity of 88% RH under the excitation wavelength of 380-780 nm. Overall, the photocatalytic hollow optical fiber developed herein provides an effective and efficient approach for the enhancement of light utilization efficiency of photocatalysts and selective CO2 reduction.

Adsorption performance of Ni(II) by KOH-modified biochar derived from different microalgae species.

Microalgae biochar is potential adsorbents to remove heavy metals from wastewater due to abundant functional groups, high porosity and wide sources, but performance is not fully developed since it depends on microalgae species attributing to distinct morphology and biomass compositions. Here, two microalgae species Chlorella Pyrenoidosa and Scenedesmus Obliquus were used for biochar preparation via KOH-modification, biochar properties and their influences on Ni(II) adsorption were investigated. Ni(II) adsorption performances responding to biochar properties and operating conditions were upgraded via progressive optimization and response surface methodology. Together, adsorption isotherms and kinetics were analyzed to obtain significant factors for Ni(II) removal. As results, 100 % of Ni(II) removal was achieved under 100 mg/L initial Ni(II) concentration as pH was higher than the biochar zero-charge point of 6.87 with low biochar dosage (0.5 g/L), which provides an efficient approach for heavy metal removal from wastewater with microalgae biochar.

Comprehensive insights into antibiotic resistance gene migration in microalgal-bacterial consortia: Mechanisms, factors, and perspectives.

With the overuse of antibiotics, antibiotic resistance gene (ARG) prevalence is gradually increasing. ARGs are considered emerging contaminants that are broadly concentrated and dispersed in most aquatic environments. Recently, interest in microalgal-bacterial biotreatment of antibiotics has increased, as eukaryotes are not the primary target of antimicrobial drugs. Moreover, research has shown that microalgal-bacterial consortia can minimize the transmission of antibiotic resistance in the environment. Unfortunately, reviews surrounding the ARG migration mechanism in microalgal-bacterial consortia have not yet been performed. This review briefly introduces the migration of ARGs in aquatic environments. Additionally, an in-depth summary of horizontal gene transfer (HGT) between cyanobacteria and bacteria and from bacteria to eukaryotic microalgae is presented. Factors influencing gene transfer in microalgal-bacterial consortia are discussed systematically, including bacteriophage abundance, environmental conditions (temperature, pH, and nutrient availability), and other selective pressure conditions including nanomaterials, heavy metals, and pharmaceuticals and personal care products. Furthermore, considering that quorum sensing could be involved in DNA transformation by affecting secondary metabolites, current knowledge surrounding quorum sensing regulation of HGT of ARGs is summarized. In summary, this review gives valuable information to promote the development of practical and innovative techniques for ARG removal by microalgal-bacterial consortia.

Photocatalytic synergistic biofilms enhance tetracycline degradation and conversion.

Tetracyclines are refractory pollutants that cause persistent harm to the environment and human health. Therefore, it is urgently necessary to develop methods to promote the efficient degradation and conversion of tetracyclines in wastewater. This report proposes a photobiocatalytic synergistic system involving the coupling of GeO2/Zn-doped phosphotungstic acid hydrate/TiO2 (GeO2/Zn-HPW/TiO2)-loaded photocatalytic optical hollow fibers (POHFs) and an algal-bacterial biofilm. The GeO2/Zn-HPW/TiO2 photocatalyst exhibits a broad absorption edge extending to 1000 nm, as well as high-efficiency photoelectric conversion and electron transfer, which allow the GeO2/Zn-HPW/TiO2-coated POHFs to provide high light intensity to promote biofilm growth. The resulting high photocatalytic activity rapidly and stably reduces the toxicity and increases the biodegradability of tetracycline-containing wastewater. The biofilm enriched with Salinarimonas, Coelastrella sp., and Rhizobium, maintains its activity for the rapid photocatalytic degradation and biotransformation of intermediates to generate the O2 required for photocatalysis. Overall, the synergistic photocatalytic biofilm system developed herein provides an effective and efficient approach for the rapid degradation and conversion of water containing high concentrations of tetracycline.

Polyacrylate stabilized ZVI/Cu bimetallic nanoparticles for removal of hexavalent chromium from wastewater.

In this work, a magnetic core-shell composite zero-valent iron/copper-polyacrylate (ZVI/Cu-PAA) was synthesized by a simple liquid-phase reduction process and used for hexavalent chromium Cr(VI) removal from wastewater. The optimization experiments show that the optimal dosages of polyacrylate and Cu are 7.00 wt% and 8.25 wt%, respectively. The maximum adsorption capacity and removal rate of Cr(VI) by ZVI/Cu-PAA reached 106.12 mg g-1 and 99.05% at pH 5.5, respectively. Furthermore, the presence of coexisting ions such as Ca2+, Mg2+, Na+, and NO3- had no significant effect on its Cr(VI) removal performance. The excellent performance of ZVI/Cu-PAA is attributed to that the modification of polyacrylate can not only give more active sites but also inhibit agglomeration of nano-metallic particles, while Cu doping promotes the electron generation and transformation of Fe(III)/Fe(II) and Cu(II)/Cu(I) redox cycles. This makes ZVI/Cu-PAA has rich active sites and excellent stability, and has broad application prospects in the remediation of Cr (VI) polluted wastewater. The magnetic core-shell composite ZVI/Cu-PAA has excellent Cr (VI) removal performance because of its rich active sites and high electron transformation efficiency.

Fiber optic sensor for nondestructive detection of microbial growth on a silk surface.

To nondestructively detect the mold growth process on silk, a coaxial concave reflection conical fiber optic sensor was developed using conical quartz fibers, fiber connectors, fiber couplers, and a plastic fixator. We established a theoretical model of this sensor and studied the influence of its structural parameters on its sensitivity, characterized the morphology of Aspergillus niger, and detected its growth process on a silk surface. A linear relationship between the sensor's output signal and the mold height was found. The sensor sensitivity, maximum detection error, and low limit of detection were 2.4 E-5 AU/µm, 7.83%, and 10 µm, respectively.

Gradient electro-processing strategy for efficient conversion of harmful algal blooms to biohythane with mechanisms insight.

Globally eruptive harmful algal blooms (HABs) have caused numerous negative effects on aquatic ecosystem and human health. Conversion of HABs into biohythane via dark fermentation (DF) is a promising approach to simultaneously cope with environmental and energy issues, but low HABs harvesting efficiency and biohythane productivity severely hinder its application. Here we designed a gradient electro-processing strategy for efficient HABs harvesting and disruption, which had intrinsic advantages of no secondary pollution and high economic feasibility. Firstly, low current density (0.888-4.444 mA/cm2) was supplied to HABs suspension to harvest biomass via electro-flocculation, which achieved 98.59% harvesting efficiency. A mathematic model considering coupling effects of multi-influencing factors on HABs harvesting was constructed to guide large-scale application. Then, the harvested HABs biomass was disrupted via electro-oxidation under higher current density (44.44 mA/cm2) to improve bioavailability for DF. As results, hydrogen and methane yields of 64.46 mL/ (g VS) and 171.82 mL/(g VS) were obtained under 6 min electro-oxidation, along with the highest energy yield (50.1 kJ/L) and energy conversion efficiency (44.87%). Mechanisms of HABs harvesting and disruption under gradient electro-processing were revealed, along with the conversion pathways from HABs to biohythane. Together, this work provides a promising strategy for efficient disposal of HABs with extra benefit of biohythane production.

A tailored bifunctional carbon catalyst for efficient glycosidic bond fracture and selective hemicellulose fractionation.

This study proposed a mild chlorination-sulfonation approach to synthesize magnetic carbon acid bearing with catalytic SO3H and adsorption Cl bifunctional sites on polydopamine coating. The catalysts exerted good textural structure and surface chemical properties (i.e., porosity, high specific surface area of >70 m2/g, high catalytic activity with 0.86-1.1 mmol/g of SO3H sites and 0.8%-1.9% of Cl sites, and abundant hydrophilic functional groups), rendering a maximum cellobiose adsorption efficiency of ∼40% within 6 h. Moreover, the catalysts had strong fracture characteristics on different α-/ß-glycosidic bonds with 85.4%-93.9% of disaccharide conversion, while selectively fractionating hemicellulose from wheat straw with 64.3% of xylose yield and 93.4% of cellulose retention. Due to the stable interaction between parent polydopamine support with Fe core and functional groups, the catalysts efficiently recovered by simple magnetic separation had good reusability with minimal losses in catalytic activity.

Thermodynamic and kinetic studies on harmful algal blooms harvesting by novel etherified cationic straw flocculant.

Harmful algal blooms (HABs) are growing threats that cause tens of billion dollars economic loss annually. Aiming at efficient disposal of HABs, a cheap and eco-friendly cationic straw was developed by etherification of wheat straw, which replaced hydroxyl groups on cellulose by quaternary ammonium groups. It endowed the cationic straw with high positive charge and achieved 93.92% of harvesting efficiency by enhancing HABs cells aggregation via charge neutralization. Different from inorganic salts-based flocculants, HABs harvesting by the cationic straw is a spontaneous and exothermic process with negative ΔG° and ΔH° under all adsorption conditions. Thermodynamics and kinetics analysis elucidated that HABs adsorption process by cationic straw were mainly driven by physical forces. Together, cationic straw preparation and HABs harvesting processes were comprehensively optimized with orthogonal experiments. The work may inspire cost-effective HABs disposal and fill knowledge gaps of process nature for HABs harvesting.

Reflective fiber-optic sensor for on-line nondestructive monitoring of Aspergillus on the surface of cultural paper relics.

A reflective fiber-optic sensor was created to realize on-line nondestructive monitoring of the growth process of Aspergillus on the surface of cultural paper relics. The sensor consisted of one tapered input and six output optical fibers. The operating principle of the device was established. The sensitivity of the sensor was checked. Sensors were used to monitor the growth of Aspergillus niger, Aspergillus flavus, and Aspergillus tamarrii on the papers. The morphology of Aspergillus was characterized. The sensor reveals a linear relationship between the output signal of the sensor and the thickness of Aspergillus biofilm with a detection limit of 10 µm.

Improving reverse osmosis concentrate treatment and nutrients conversion to Chlorella vulgaris bioenergy assisted with granular activated carbon.

Landfill leachate (LL), especially the reverse osmosis concentrate (ROC), is a societal burden due to high toxicity but may have intrinsic values attributing to copious nutrients and organics. ROC bioremediation by microalgae has attracted much attentions benefiting from its extra advantage of bioenergy production. However, efficient microalgae cultivation with ROC is still a challenging task attributing to notorious ROC characteristics, like high chromaticity and toxicity. To alleviate these negative influences, a technique integrating granular activated carbon (GAC) pretreatment and microalgae bioremediation was proposed, with which nitrogen and phosphorus removal efficiencies achieved 100% along with an optimized microalgal biomass concentration of 1.44 g/L and lipid yield of 482.4 mg/L. Furthermore, a total volumetric energy yield of 33.6 kJ/L was acquired, which was conducive to realize energy valorization. The visualization evidence of three-dimensional fluorescence spectroscopy revealed chromaticity degradation mechanism of ROC as humic acids reduction and transfer to family of soluble microbial by-products. Meanwhile, contributions of GAC adsorption and microalgae assimilation on nutrients removal were analyzed. Together, this work provides a promising method and valuable information for ROC bioremediation with microalgae.

Peroxymonosulfate activated by photocatalytic fuel cell with g-C3N4/BiOI/Ti photoanode to enhance rhodamine B degradation and electricity generation.

The development of traditional photocatalytic fuel cell (PFC) is severely hindered by poor visible-light response and limited reaction space. In this study, a visible-light responsive PFC with g-C3N4/BiOI/Ti photoanode was proposed and applied to activate peroxymonosulfate (PMS) to degrade rhodamine B. The degradation rate, maximum power density and maximum photocurrent density of the PMS/PFC system were respectively 95.39%, 103.87 µW cm-2 and 0.62 mA cm-2, which was respectively 1.28, 2.18, and 1.98 times that of PFC. The excellent performance is attributed to the production of more reactive oxygen species and the extension of the reaction space range after the activation of PMS. The activation pathway of PMS and charge transfer pathway of the photoanode were discussed in detail, and it was proposed that PMS was activated by Z-scheme heterojunction g-C3N4/BiOI/Ti photoanode.

Analysis of Distortion Based on 2D MEMS Micromirror Scanning Projection System.

To analyze the distortion problem of two-dimensional micro-electromechanical system (MEMS) micromirror in-plane scanning, this paper makes a full theoretical analysis of the distortion causes from many aspects. Firstly, the mathematical relations among the deflection angle, laser incidence angle, and plane scanning distance of the micromirror are constructed, and the types of projection distortion of the micromirror scanning are discussed. Then the simulation results of reflection angle distribution and point cloud distribution are verified by MATLAB software under different working conditions. Finally, a two-dimensional MEMS micromirror scanning projection system is built. The predetermined waveform can be scanned and projected successfully. The distortion theory is proved to be correct by analyzing the distortion of the projection images, which lays a foundation for practical engineering application.

Dual-peak long period fiber grating coated with graphene oxide for label-free and specific assays of H5N1 virus.

Avian influenza is an acute infectious disease caused by the avian influenza virus (AIV), which has caused enormous economic losses and posed considerable threats to public health. This study aimed to demonstrate an immunosensor based on dispersion turning point long-period fiber grating (DTP-LPFG) integrated with graphene oxide (GO) for the specific detection of a type of AIV H5N1 virus. LPFG was designed to work at DTP, whose dual-peak spacing was very high sensitive to a refractive index. Anti-H5N1 monoclonal antibodies were covalently bonded with the GO film on the fiber surface, thus constructing an immunosensor for the label-free and specific detection of the H5N1 virus. The proposed method was capable of the reliable detection of H5N1 virus with the limit of detection as low as ~1.05 ng/ml within the large range of 1 ng/mL to 25 µg/mL. More importantly, immunoassays of the whole H5N1 virus in clinical samples further confirmed that the GO-integrated DTP-LPFG immunosensor showed very high specificity to the H5N1 virus and demonstrated great potential for clinical use.

Highly efficient reverse osmosis concentrate remediation by microalgae for biolipid production assisted with electrooxidation.

Phytoremediation of reverse osmosis concentrate (ROC) with microalgae can simultaneously achieve multi-functions of ROC treatment, CO2 mitigation and microalgae biolipid production. But the performances are usually inhibited by high free ammonia nitrogen (FAN) concentration and chromaticity of ROC. To offset these negative effects, an integrated technique including electrooxidation pretreatment and Chlorella vulgaris remediation was proposed, in which the ROC was first pretreated with electrooxidation to decrease FAN and chromaticity, and then the oxidized ROC was remediated with microalgae to reclaim nutrients and produce biolipid. Results showed that FAN was sharply reduced from 53.0 mg N/L to 13.9 mg N/L and chromaticity was decreased from 1600 to 100 Pt-Co via electrooxidation. Possible reaction mechanism of nutrients removal was discussed via electron mass balance. Explanation on chromaticity decrease was revealed by analyzing humic acid conversion path with fluorescence characteristics. During microalgae remediation process, nutrients removal rate, microalgae biomass concentration and lipid yield were effectively enhanced in electrooxidized ROC. Energy balance analysis indicated that microalge lipid energy under current density of 3.25 mA/cm2 basically compensated total input energy despite ROC sterilization. This work provided a promising strategy for large-scale ROC treatment and microalgae biolipid production.

Monitoring Microalgal Biofilm Growth and Phenol Degradation with Fiber-Optic Sensors.

Simple D-type plastic optical fiber (POF) probes (i.e., sensor, reference, and photochemical probes) were created to accurately monitor the progression and phenol degradation of a Chlorella vulgaris biofilm. The sensor and reference probes were used to monitor the biofilm growth (thickness). The sensor probe, which consisted of a D-shaped POF and Canada balsam doped with GeO2 (CBG) coating, was developed to monitor the biofilm growth and change in the liquid-phase composition and its concentration inside the biofilm. The reference probe, which comprised a D-shaped POF, CBG coating, and glass fiber membrane (to separate the liquids from Chlorella vulgaris), was used to measure the response to changes in the liquid phase. A model was developed to demonstrate the accurate measurement of the biofilm thickness. The photochemical POF probe was coupled with a high-permselectivity phenol polymer membrane to monitor the phenol concentration and analyze the degradation time of 50 mg/L phenol with microalgal biofilms. A fixed relationship was obtained between the biofilm sensor output information and biofilm thickness for a biofilm thickness range of 0-290 µm with a periodic supply of 50 mg/L phenol solution. The highest phenol degradation rate occurred at a biofilm thickness of 191-222 µm. The proposed system can be used to investigate microalgal biomass and can provide a promising avenue for research on renewable resources and pollutant degradation.

A novel superparamagnetic micro-nano-bio-adsorbent PDA/Fe3O4/BC for removal of hexavalent chromium ions from simulated and electroplating wastewater.

In order to improve the adsorption efficiency of the adsorbent and solve the problem of separation difficulty, a novel superparamagnetic micro-nano-bio-adsorbent (PDA/Fe3O4/BC) was prepared by in situ self-assembly of polydopamine (PDA). The results of scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier transform infrared spectrometer (FT-IR), X-ray photoelectron spectrometer (XPS), and vibrating sample magnetometer (VSM) characterization showed that the size of bio-adsorbent was about 200 nm. PDA and Fe3O4 modifications increased the specific surface area of adsorbent, changed the surface functional group of biochar (BC), and made the adsorbent have super-high magnetization (294.76 emu g-1). PDA/Fe3O4/BC was applied to treat Cr wastewater. The results show that the adsorption of Cr by PDA/Fe3O4/BC includes single-layer and multilayer adsorption. The adsorption follows the pseudo-second-order kinetic model. The adsorption is spontaneous and endothermic, and its maximum adsorption capacity and activation energy are 25.25 mg g-1 at 318 K and 23.108 kJ mol-1, respectively. After adsorption treatment, PDA/Fe3O4/BC still possesses high magnetization (233.04 emu g-1). PDA/Fe3O4/BC can treat actual electroplating wastewater with Cr(VI) concentration from 20 mg L-1 to less than 0.2 mg L-1, which met the PRC discharge standard (GB/21900-2008) of electroplating pollutants. Graphical abstract.

Monitoring Biohydrogen Production and Metabolic Heat in Biofilms by Fiber Bragg Grating Sensors.

A fiber Bragg grating (FBG) was created to accurately and simultaneously monitor the biohydrogen and metabolic heat production in biofilms containing Rhodopseudomonas palustris CQK-01 photosynthetic bacteria (PSB). The proposed hydrogen sensor was made from an FBG unit separated into two regions by a wet etching process; a thin region with a diameter of 15 µm was employed to monitor the temperature. A smaller region of the etched FBG with a diameter of 8.0 µm was coated with a 50 nm-thick Pd film by sputtering to determine the responses to the temperature and hydrogen concentration. To monitor the biohydrogen production and metabolic heat within the biofilms, three FBGs were evenly distributed in a polydimethylsiloxane channel (biofilm carrier) with vertical distances of 80 µm. In addition, the thickness, surface morphology, active biomass, and porosity of the biofilms were investigated. The FBG sensor can rapidly and accurately determine the difference in Bragg wavelength shifts caused by changes in the hydrogen concentration and temperature. The measured biohydrogen concentration is highly correlated with the real biohydrogen production with a correlation of 0.9765. The biohydrogen production capacity of PSB in the surface layer is much higher than that internally because of sharp decreases in the active biomass and porosity from the surface to within the biofilm. The highest biohydrogen concentration is obtained at 1.218 × 104 ppm for a biofilm thickness of 165 µm, and the temperature difference from metabolic heat production is ∼1.1 °C in the biofilm culture.

Photochemical reflective optical fiber sensor for selective detection of phenol in aqueous solutions.

A photochemical fiber-optic sensor was developed by integrating a plastic optical fiber (POF), polymer membrane, gold mirror, and TiO2-based composite, and was shown to sensitively and selectively detect phenol in aqueous solution. The sensing element consisted of a thinned POF and visible-light-driven SiO2/N-doped TiO2 coating. The gold mirror was used to develop a reflective POF probe. The polymer membrane with high phenol permselectivity was employed to form a micro-channel between the membrane and probe. Our findings highlight the sensor's capability of phenol detection in aqueous solutions with high sensitivity of 0.294×10-3 (mg·L-1)-1, pH immunity ranging from 2.0 to 14.0, and high selectivity with a limit of detection of 30 µg·L-1.

Microalgal lipids production and nutrients recovery from landfill leachate using membrane photobioreactor.

The aim of this work was to realize high-efficiency nutrients recovery from landfill leachate (LL) for microalgal lipids production. Negative effects of LL on microalgal lipid synthesis was revealed and a scalable membrane-based tubular photobioreactor (SM-PBR) was proposed to offset these negative effects. Microalgal biomass concentration was improved from 0 g/L in the traditional PBR to 2.13 g/L in the SM-PBR. Major operating conditions were optimized to enhance nutrients recovery and lipid productivity. The maximum N recovery efficiency of 74.31% and the maximum daily lipid production of 404.98 mg/d were obtained under the volume ratio of 5:3 (microalgae culture/LL stream) and phosphate feeding concentration of 50 mg/L. The obtained lipid was convinced to have a good combustion and anti-degradation property, with high cetane number (>52%) and low linolenic acid content (<12%). The SM-PBR provided a feasible approach for large-scale microalgal lipid production with LL.