Inactivation Of Algae Research Articles

Low-frequency ultrasound assisted contact-electro-catalysis for efficient inactivation of Microcystis aeruginosa

Frequent cyanobacterial blooms pose a serious threat to the aquatic ecosystem and human health, so developing an efficient algae removal method is a long-term goal for bloom management. Current technologies for algal bloom control need urgent improvement in terms of algicide recovery, eco-friendliness and cost. Here we propose a contact-electro-catalytic method, using polytetrafluoroethylene (PTFE) film as a reusable catalyst. This contact-electro-catalytic approach involves the generation of reactive oxygen species (e.g., O2•–, HO•, 1O2 and H2O2) through water-PTFE contact electrification under the low-frequency ultrasonic waves, facilitating the inactivation of algae. The removal rate of the cyanobacterium Microcystis aeruginosa (M. aeruginosa) exposured to the water-PTFE contact-electro-catalytic system is almost five times greater than that of ultrasound alone after 5 h. A mechanistic investigation revealed that the contact-electro-catalytic system damaged the photosynthetic activity, antioxidant system and membrane integrity of the cells. Additionally, LC-MS metabolomic analysis indicated that this system caused substantial significant disruptions in the TCA cycle, amino acid metabolism, purine metabolism and phospholipid metabolism. Three-dimensional fluorescence spectroscopy suggested contact-electro-catalysis could further availably degrade the organic matter. We anticipate that this method can provide an eco-friendly, highly efficient and economic approach for effective control of harmful algal blooms.

Simultaneous inactivation of Microcystis aeruginosa and degradation of microcystin-LR in water by activation of periodate with sunlight

Harmful algal blooms pose tremendous threats to ecological safety and human health. In this study, simulated solar light (SSL) irradiation was used to activate periodate (PI) for the inactivation of Microcystis aeruginosa and degradation of microcystin-LR (MC-LR). We found that PI-SSL system could effectively inactivate 5 × 106 cells·mL−1 algal cells below the limit of detection within 180 min. ·OH and iodine (IO3· and IO4·) radicals generated in PI-SSL system could rupture cell membranes, releasing intracellular substances including MC-LR into the reaction system. However, the released MC-LR could be degraded into non-toxic small molecules via hydroxylation and ring cleavage processes in PI-SSL system, reducing their environmental risks. High algae inactivation performance of PI-SSL system in solution with a wide pH range (3–9), with the coexisting anions (Cl−, NO3− and SO42−) and the copresence of natural organic matters (humic acid and fulvic acid), real water (lake water and river water), as well as in continuous-flow reactor (14 h) were also achieved. In addition, under natural sunlight irradiation, effective algae inactivation could also be achieved in an enlarged reactor (1 L). Overall, our study showed that PI-SSL system could avoid the inference by the background substances and could be employed as a feasible technique to treat algal bloom water.

Oxidation effects on Microcystis aeruginosa inactivation through various reactive oxygen species: Degradation efficiency, mechanisms, and physiological properties

The study investigated the inactivation of Microcystis aeruginosa using a combined approach involving thermally activated peroxyacetic acid (Heat/PAA) and thermally activated persulfate (Heat/PDS). The Heat/PDS algal inactivation process conforms to first-order reaction kinetics. Both hydroxyl radical (•OH) and sulfate radical (SO4-•) significantly impact the disruption of cell integrity, with SO4-• assuming a predominant role. PAA appears to activate organic radicals (RO•), hydroxyl (•OH), and a minimal amount of singlet oxygen (1O2). A thorough analysis underscores persulfate's superior ability to disrupt algal cell membranes. Additionally, SO4-• can convert small-molecule proteins into aromatic hydrocarbons, accelerating cell lysis. PAA can accelerate cell death by diffusing into the cell membrane and triggering advanced oxidative reactions within the cell. This study validates the effectiveness of the thermally activated persulfate process and the thermally activated peroxyacetic acid as strategies for algae inactivation.

Innovative reverse-irradiation UV photocatalytic system for algae inactivation from eutrophic water: Limitation breakthrough of algae blocking and light decay

The particle blocking and light energy decay were major limitations in algae-rich water treatment by photo-catalysis. This study developed an effective photocatalytic system in innovative reverse-irradiation mode to overcome these limitations towards improving algae inactivation. Suitable light transmittance and reverse photocatalytic activity of TiO2 thin film were obtained by deposition and calcination optimization, with the optimal UV wavelength at 365 nm. Such reverse-irradiation photocatalytic system presented sustainable and durable algae degradation performance in long-term operation (7 cycles), which generated reactive oxygen species and increased superoxide dismutase activity in two-stage catalytic oxidation process. The algae cells were lysed for intracellular substance solubilization in 2-h treatment, followed by numerous degradation and removal of the dissolved cytoplasm in 2–4 h. Reverse-irradiation photocatalytic oxidation dominantly contributed 62.66–85.60 % of overall algae inactivation, while environment and photolysis provided feeble contributions of 0–4.80 % and 14.40–32.54 %, respectively. As such, 19.79 % of algae cells were lyzed, with the degradations of intracellular chlorophyll a (26.42 %) and proteins (58.14 %). Particularly, the innovative photo-catalysis in reverse-irradiation mode presented much greater performances in algae removal than those in traditional forward-irradiation mode at the long light transmission path (>1.75 cm) and high algae density (>2.8 × 107 cells/L). The reverse-irradiation photo-catalysis not only overcame limitations of algae blocking and light decay, but also remarkably inhibited residual algae regrowth, contributing to the continuous algae inactivation. Moreover, the energy-saving efficiency of 160 % was achievable due to photocatalytic promotion, contributing to economic benefit of 87.59 CNY/(m3 order) and carbon-emission reduction of 0.091 ton CO2/(m3 order). The findings provided novel insights into photo-catalysis promotion and limitation breakthrough from system configuration modification.

Inactivation of harmful cyanobacteria Microcystis aeruginosa by Cu2+ doped corn stalk biochar treated with different pyrolysis temperatures

In this study, biochars (BCs) derived from corn stalk treated at various pyrolysis temperatures (350–950 °C) were prepared and then loaded with Cu2+ to form highly efficient algaecide, i.e. Cu2+-doped BC composites (Cu-BCs). The results showed BCs pyrolyzed at higher temperatures suppressed the growth of Microcystis aeruginosa in the order of BC550 ≫ BC750 > BC950, while BC350 accelerated cell growth due to the release of inorganic nutrients. The difference could be attributed to the physicochemical characteristics, including specific surface area, adsorption capacity of nutrients and the presence of particularly persistent free radicals. Furthermore, Cu-BCs exhibited the improved inactivation performance, but the 72 h growth inhibition rates and reaction activities of Cu-BCs were still influenced by the Cu2+ loading ratio and pyrolysis temperature. These results, reported for the first time, demonstrated the algae inactivation efficiency of pristine BCs, and Cu-BCs were principally manipulated by the biochar pyrolysis temperature.

Reinvestigation on the Mechanism for Algae Inactivation by the Ultraviolet/Peracetic Acid Process: Role of Reactive Species and Performance in Natural Water.

This study provided an in-depth understanding of enhanced algae inactivation by combining ultraviolet and peracetic acid (UV/PAA) and selecting Microcystis aeruginosa as the target algae species. The electron paramagnetic resonance (EPR) tests and scavenging experiments provided direct evidence on the formed reactive species (RSs) and indicated the dominant role of RSs including singlet oxygen (1O2) and hydroxyl (HO•) and organic (RO•) radicals in algae inactivation. Based on the algae inactivation kinetic model and the determined steady-state concentration of RSs, the contribution of RSs was quantitatively assessed with the second-order rate constants for the inactivation of algae by HO•, RO•, and 1O2 of 2.67 × 109, 3.44 × 1010, and 1.72 × 109 M-1 s-1, respectively. Afterward, the coexisting bi/carbonate, acting as a shuttle, that promotes the transformation from HO• to RO• was evidenced to account for the better performance of the UV/PAA system in algae inactivation under the natural water background. Subsequently, along with the evaluation of the UV/PAA preoxidation to modify coagulation-sedimentation, the possible application of the UV/PAA process for algae removal was advanced.

Control of cyanobacterial bloom and purification of bloom-laden water by sequential electro-oxidation and electro-oxidation-coagulation

The outbreaks of cyanobacterial blooms have caused severe threat to aquatic ecosystem and public health. In this work, electrochemical technology with RuO2/IrO2/Ti (RIT) or/and Al as anode for cyanobacterial bloom control and simultaneous water purification were studied. Compared with RIT-Al and Al electrodes, RIT exhibited the highest effects on bloom algae inactivation and inhibition of algae regrowth. Live/dead analysis, SEM, intracellular reactive oxygen species (ROS) and antioxidant system activities revealed that RIT could disintegrate bloom flocs and damage embedded algal cells due to high intensity of oxidation. With the lysis of cyanobacterial bloom, high content of intracellular compounds containing organic carbon, nitrogen and phosphorus released, necessitating water quality restoration. In the subsequent water purification process, RIT-Al overtook RIT and Al in removal of organic and nutrient pollutants due to the complex effects of electro-oxidation, coagulation, co-precipitation, electro-nitrification and electro-denitrification. Therefore, sequential electro-oxidation and electro-oxidation-coagulation process was an effective method for control cyanobacteria bloom and simultaneous removal of DOM, microcystin-LR (MC-LR), nitrogen and phosphorus, which is a promising technology.

Triboelectric-photocatalytic coupling enhanced photogenerated electrons and holes utilization for efficient algal inactivation

Algal blooms have become a challenging problem in conventional water treatment processes due to numerous negative effects on human health and ecosystems. Photocatalysis has turned out to be a promising solution with the environmental and economic benefits beheld, but the rapid recombination of photogenerated electron and hole inhibited the application in practice. This study proposed a rotating triboelectric nanogenerator (R-TENG) as a self-powered bias for photocatalysis to enhance the algal removal efficiencies. R-TENG harvest waste water wave energy from coagulation tank to convert it into stable DC voltage (31 V) and DC current (27 μA). TiO2 nanotubes (TNT) serving as the anode in the photocatalysis with TENG system achieved complete inactivation of algae (>97 %) after 7 h of reaction, which was increased by 13.9 % compared with photocatalysis. This enhanced performance was attributed to the improvement of active species generation (e.g., •O2-, •OH and h+). During algal inactivation, the active species destroyed photosynthetic activity (decline of Chlorophyll a), antioxidant system (decrease of superoxide dismutase, catalase and malondialdehyde) and membrane in algal cells. Given the ubiquitous existence of algal cells in surface water, this work offers a novel method to develop high-performance electro-assisted photocatalysis for algal removal.

Enhanced inactivation of Microcystis aeruginosa by heterogeneous interfacial Ag2MoO4/TACN under visible light

A novel photocatalytic material Ag2MoO4/TACN was synthesized, and the heterogeneous interfacial effect between them enhanced its photocatalytic algae removal performance. Meanwhile, the crystal phase change of Ag2MoO4 was also found during the recombination process, which cramped the band gap width from 3.35 to 3.06 eV. The improved algal removal efficiency of the synthesized photocatalyst was clearly demonstrated when nearly 100 % of Microcystis aeruginosa got removed under 3 h illumination. Moreover, better inactivation effect was observed under alkaline and neutral conditions. From the results, possible mechanisms for the photocatalytic activities were proposed. ROS (·OH, and·O2−), h+ and Ag+ produced by Ag2MoO4/TACN were the main substances causing algae inactivation, as they destroy the normal functions of cell membrane and consequently lead to the leakage of electrolytes as well as algal organic matter. In addition, under the continuous attack of ROS and Ag+, the photosynthetic and metabolic activities of algal cells were hindered, while the PB content, SOD and CAT activities were also continuously reduced, leading to the mortality of algal cells. Finally, recycling experiments confirmed the recyclability and reusability of Ag2MoO4/TACN, further illustrating its potential as a promising photocatalyst for practical applications.

The selection of floating photocatalyst carrier and algae inhibition effect of Karenia mikimotoi based on SNP-TiO2@Cu-MOF under visible light

Photocatalytic technology for inactivating harmful algae has shown great research potential, in previous work, a kind of non-noble metal modified TiO2 loading onto copper metal organic framework (SNP–TiO2@Cu-MOF) was proved to show high removal efficiency against Karenia mikimotoi (K. mikimotoi). However, the recovery problem of powdered photocatalysts and its potential ecological hazards were still existed. In order to solve this, this study selected four macro-floating carriers and loaded photocatalyst on their surface. The floating photocatalyst with luffa sponge and expanded perlite as carriers were prepared by hydrothermal synthesis, and the floating photocatalyst with melamine sponge and polyurethane sponge as carriers were prepared by sodium alginate fixation method. The photocatalyst was firmly supported on the carriers, and the octahedral structure of SNP-TiO2@Cu-MOF photocatalyst could be well retained by hydrothermal synthesis. The advantages of sodium alginate fixation method were simple preparation process and low cost. The specific surface area of melamine foam photocatalyst (MF-P) was the highest, 28.47 m2/g, and the algae inactivation rate was also the best, which was 98.68% in 6 h. The MF-P group showed a decrease of 81.8% in soluble protein content and 81.4% in chlorophyll-a content of K. mikimotoi after 1 h of photocatalysis, respectively. The four photocatalysts showed good recyclability, and especially in MF-P group. The inactivation efficiency was still as high as 94.12% after four experiments. The floating photocatalyst would lay the foundation for further application of photocatalytic materials for algae removal.

Synthesis of Cu2+ doped biochar and its inactivation performance of Microcystis aeruginosa: Significance of synergetic effect

The harmful cyanobacteria bloom is frequently occurring in the aquatic environment and poses a tremendous threat to both aquatic organisms and ecological function. In this study, a series of Cu2+ doped biochar (BC) composites (Cu–BCs) with different loading ratios (0.1 %-5 wt %) (Cu-BC-0.1/0.5/1/2.5/5) was successfully fabricated through a one-step adsorption method for in-situ inactivation of Microcystis aeruginosa and simultaneous removal of microcystin-LR (MC-LR). Compared with the single BC/CuSO4 and other Cu–BCs composites, the Cu-BC-2.5 exhibited the best algae inactivation performance with the lowest 72 h medium effective concentration (EC50) value of 0.34 mg/L and highest chlorophyll α degradation efficiency of 8.31 g/g. Notably, the as-prepared Cu-BC-2.5 maintained good inactivation performance in the near-neutral pH (6.5–8.5), and the presence of humic acid and salts such as Na2CO3 and NaCl. The outstanding inhibitory effect of the Cu-BC-2.5 could be explained by the synergetic effect between biochar and Cu2+, which greatly elevated reactive oxygen species (ROS) intensity and in turn led to severe membrane damage and collapse of the antioxidant system. Additionally, the Cu-BC-2.5 could simultaneously remove the released microcystin-LR (MC-LR) throughout the inactivation process and prevent secondary pollution, thus offering a new insight into the alleviation of harmful cyanobacteria in aquatic environment.

Activation of peroxymonosulfate by La2CuO4 perovskite for synergistic removal of Microcystis aeruginosa and microcystin-LR in harmful algal bloom impacted water

The cyanobacterial blooms induced water safety problems have attracted tremendous concerns due to the adverse influences on aqueous ecosystem and human health. This study developed a novel perovskite-type catalyst for heterogeneous peroxymonosulfate (PMS) activation as an emergency measure to remove harmful algae. The results indicated that significant removal efficiency of Microcystis aeruginosa cells (97%) and chlorophyll-a (100%) was achieved within 20 min in La2CuO4/PMS system without significant release of dissolved organic carbon and metals in water. •OH, SO4•-, 1O2 and •O2- generated were all responsible for algae inactivation and subsequent algal organic matters removal. Moreover, the heterogeneous catalytic mechanism was proposed that La portion in La2CuO4 favored the cells destabilization by increasing zeta potential of algae suspension, while variable Cu portion facilitated the electron transfer to improve the yields of •OH and SO4•-. This study demonstrates that the new catalytic PMS process promises viable and effective control of harmful algal bloom impacts in water treatment.

Inactivation of Microcystis aeruginosa by H2O2 generated from a carbon black polytetrafluoroethylene gas diffusion electrode in electrolysis by low-amperage electric current

Frequent outbreaks of cyanobacterial blooms have seriously threatened aquatic ecological environments and human health. Electrolysis by low-amperage electric current is effective for algae inactivation; however, it has no selectivity. Hydrogen peroxide (H2O2) is considered to be an efficient and selective suppressor of algae. Therefore, it is necessary to develop an electrode that can generate H2O2 to improve electrolysis technology. In this study, a carbon black polytetrafluoroethylene gas diffusion electrode (C-PTFE GDE) with good stability was prepared by a simple adhesive coating method. Then, the inactivation of Microcystis aeruginosa was conducted with electrolysis by low-amperage electric current using Ti/RuO2 as the anode and C-PTFE GDE as the cathode. When the electrode spacing was 4 cm, the current density was 20 mA cm−2, and the gas flow was 0.4 L min−1, 85% of the algae could be inactivated in 20 min. Comparing the inactivation effect of the electric field and electrogenerated oxidants, it was found that electrolysis more rapidly and strongly inactivated algae when an electric field existed. However, electrogenerated oxidants dominated algae inactivation. The concentration of H2O2 was as high as 58 mg L−1, while the concentration of chlorines was only 0.57 mg L−1, and the generation rate of H2O2 was 65 times that of chlorines. Consequently, electrogenerated oxidants dominated by H2O2 attacked photosystem II of the algae and caused oxidative damage to membrane lipids, affecting the photosynthetic capacity. Eventually, most of the algae were inactivated. The study suggested that C-PTFE GDE was promising for the inactivation of Microcystis aeruginosa in this electrochemical system.

Highly efficient and recyclable Z-scheme heterojunction of Ag3PO4/g-C3N4 floating foam for photocatalytic inactivation of harmful algae under visible light

Harmful algal blooms (HABs) have frequently occurred worldwide, causing marine ecosystems and human health risks. As an advanced and green oxidation technology, photocatalysis has potential to remove red tide algae using solar energy. Herein, in this work, Z-scheme photocatalysts of Ag3PO4/g-C3N4 (APCN) floating foam with different mass ratios were fabricated for the algae inactivation. Under visible light irradiation, the 0.10APCN (0.10 mM AgNO3) composite photocatalyst could cause 91.8% of the loss in Karenia mikimotoi (K. mikimotoi) cell viability following 24 h and the removal rate of algae could reach to 86% after five successive cycles. The underlying mechanism of photocatalytic inactivation of harmful algae is proposed in this system. The photosynthetic efficiency of harmful algae is inhibited with the decrease of photosynthetic pigments, which are inactivated by the high levels of reactive oxygen species (ROS) (superoxide radical •O2− and hydroxyl radical •OH) produced in Z-scheme photocatalytic system of the Ag3PO4/g-C3N4 heterojunction under visible light. Meanwhile, the activities of antioxidant enzymes (i.e. POD, APX and SOD) are up-regulating with the overproduction of ROS going into the algae, causing the cytotoxicity and apoptosis of algae. This work not only reveals the mechanisms of photocatalytic inactivation of harmful algae, but also guides the design the construction of high active composite photocatalysts, and thus provides theoretical and practical significance for highly efficient and recyclable prospect of controlling of harmful algae.

Magnetic-field-induced simultaneous charge separation and oxygen transfer in photocatalytic oxygen activation for algae inactivation

Photocatalytic oxygen activation is an excellent strategy for algae control in water. However, the fast recombination of photogenerated charge and slow rate of oxygen transfer limit the reactive oxygen species generation efficiency for algae inactivation. Herein, to solve above issues, magnetic field was introduced to the BiO2−x/Bi3NbO7 system to effectively covert oxygen into reactive radicals. The electrochemical experiment and DFT calculation results indicated the charge separation could be accelerated by the Lorentz force generated by the magnetic field, resulting in increase of electron concentration. Meanwhile, the value of volumetric gas-liquid mass transfer coefficient was increased by 59.79 % with magnetic field, thus more oxygen could be reduced to superoxide radical. Photocatalytic algae inactivation rate by BiO2−x/Bi3NbO7 with magnetic field could be increased by 2.07 times than that without magnet filed. This work further extends the strategy of using magnetic field to simultaneously facilitate the charge separation and oxygen transfer rate.

Removal of algae and algogenic odor compounds via combined pre-chlorination and powdered activated carbon adsorption for source water pretreatment

This study investigated the combination sequence and time interval of chlorination and powdered activated carbon (PAC) adsorption for the control of algae inactivation, algogenic odor removal, and disinfection by-product (DBP) formation. Results indicated that pre-chlorination/post-PAC exhibited the highest algae removal efficiency in all sequential combinations of PAC adsorption and chlorination, while it had displayed slight effect on the removal of DBPs. The evaluated sequential combinations all had significant effect on the removal of odor. Nevertheless, prolonged time interval between chlorination and PAC adsorption exhibited enhanced control of algae and odor compounds in all experiments; with increasing time interval from 0 to 15 min in pre-chlorination/post-PAC process, the removal efficiency of Chl-a, algal cell viability, GSM, and 2-MIB increased by 46%, 15%, 15% and 23%, respectively. In the combined processes, the odor removal efficiency was positively correlated with PAC dosage but negatively correlated with chlorine dosage. Furthermore, PAC addition could effectively reduce the total DBP yields, especially the N-DBPs. This study can provide a better understanding of improving in-situ operation of the pre-chlorination and PAC dosing systems for source water pretreatment.

Photocatalytic O2 activation enhancement and algae inactivation mechanism of BiO2−x/Bi3NbO7 van der Waals heterojunction

The removal of algae by reactive oxygen species (ROS) through photocatalytic O2 activation is still a challenge. Herein, we constructed a van der Waals (VDW) heterojunction photocatalyst by coupling BiO2−x with Bi3NbO7 for photocatalytic inactivation of Microcystic aeruginosa and photodegradation of Microcystin-LR. The oxygen vacancies in BiO2−x/Bi3NbO7 can effectively promote the chemisorption of O2, and the VDW force can drive the photoelectrons in Bi3NbO7 transfer to BiO2−x through S-scheme transfer path, resulting more electrons reduce O2 to·O2-. Hence, photocatalytic inactivation of algae by BiO2−x/Bi3NbO7 is 14.17 and 19.05 times higher than BiO2−x and Bi3NbO7, respectively. During the photocatalysis, the·O2- damages the antioxidant system and cell membrane of algae, resulting in the release of organic matter and Microcystin-LR and finally causing the death of algae. The three-dimensional fluorescence spectroscopy indicates BiO2−x/Bi3NbO7 can further availably photodegrade the organic matter, and four possible photodegradation pathways of MC-LR are proposed.

Maximizing the utilization of photo-generated electrons and holes of g-C3N4 photocatalyst for harmful algae inactivation

• Sulfuric acid exfoliated C 3 N 4 (S-CN) exhibited excellent algal removal activity. • Positive charge, smaller size, ultrathin structure contributed to the high activity. • Addition of H 2 O 2 can further improve the efficiency of algal removal. • The released and leaked organic matters from algal cells can also be removed. Effective contact between photocatalysts and algal cells is important for algae inactivation because of the efficient transfer/utilization of photo-generated charges. Herein, sulfuric acid exfoliated C 3 N 4 (S-CN) is found to be efficient for algae inactivation under visible light irradiation (92% removal rate within 3.5 h). The high performance can be ascribed to the positive surface charge (S-CN can be rapidly adsorbed on the surface of algal cells) and small sized/ultrathin structure (high separation/transfer efficiency of charges). Furthermore, the efficiency can be improved significantly by H 2 O 2 addition (94.3% removal rate within 1.5 h). The addition of H 2 O 2 not only reduce the recombination of photo-induced carriers but also generate more ·OH. Decreased photosynthetic activity, membrane damage and cell rupture occur in the inactivation process. In addition, the organic matters release and leak from algal cells are also partly removed. The present work has great significance in the application of photocatalytic technology for algal remediation.

Photocatalytic inactivation of algae in a fluidized bed photoreactor with an external magnetic field

Practical applications of photocatalysis in algae removal often involve the use of photoreactors, which can be of many different configurations. In this study, a fluidized bed photoreactor (FBPR) with an external magnetic field was designed and constructed to achieve algae inactivation continuously and stably. Magnetic photocatalyst ZnFe2O4/Ag3PO4/g-C3N4 attached to Fe3O4 aggregate, was dispersed and fixed at the bottom of the reactor to form a flower-like structure, which can not only increase the effective irradiation area of the photocatalyst, but also enhances mass transfer by inducing flow disturbance. Under the optimal operating conditions, i.e., 0.04 m/s flow rate, 200 mT magnetic field strength, and 0.025 g photocatalyst loading, the photoreactor can effectively remove algae cells within 6 h. During the continuous operation experiment, the quality of the magnetic photocatalyst and aggregate did not decrease significantly, and there was still a 90% removal efficiency after 18 h of continuous operation. Furthermore, in the experiment where humic acid was added to simulate actual water environment, certain advantages can still be observed with the FBPR. As a continuous reactor using a magnetic photocatalyst, the FBPR has the characteristics of high availability, low cost, and low energy consumption.

Preparation of floating BiOCl0.6I0.4/ZnO photocatalyst and its inactivation of Microcystis aeruginosa under visible light

Frequent occurrence of harmful algal blooms has already threatened aquatic life and human health. In the present study, floating BiOCl0.6I0.4/ZnO photocatalyst was synthesized in situ by water bath method, and and applied in inactivation of Microcystis aeruginosa under visible light. The composition, morphology, chemical states, optical properties of the photocatalyst were also characterized. The results showed that BiOCl0.6I0.4 exhibited laminated nanosheet structure with regular shape, and the light response range of the composite BZ/EP-3 (BiOCl0.6I0.4/ZnO/EP-3) was tuned from 582 to 638 nm. The results of photocatalytic experiments indicated that BZ/EP-3 composite had stronger photocatalytic activity than a single BiOCl0.6I0.4 and ZnO, and the removal rate of chlorophyll a was 89.28% after 6 hr of photocatalytic reaction. The photosynthetic system was destroyed and cell membrane of algae ruptured under photocatalysis, resulting in the decrease of phycobiliprotein components and the release of a large number of ions (K+, Ca2+ and Mg2+). Furthermore, active species trapping experiment determined that holes (h+) and superoxide radicals (·O2−) were the main active substance for the inactivation of algae, and the p-n mechanism of photocatalyst was proposed. Overall, BZ/EP-3 showed excellent algal removal ability under visible light, providing fundamental theories for practical algae pollution control.