Biosorption performance,combustion behavior,and leaching characteristics of olive solid waste during the removal of copper and nickel from aqueous solutions

Several researchers have proved that agricultural by-products constitute good adsorbents for removing heavy metals from aqueous solution. However, few investigations have identified efficient strategies for the adsorbent′s regeneration. Hence, a global methodology for the removal of copper and nickel metals from wastewater including metal biosorption, thermal treatment and residual ash landfill is proposed. In order to validate this strategy, olive solid waste (OSW), provided by an olive oil mill from Tunisia, were used to remove copper and nickel on batch experiments. Copper and nickel were adsorbed on a monolayer of OSW surface with maximal adsorption capacity (q _max) of 3.6 and 1.7 mg g^?1, respectively. Contaminated OSW with copper and nickel were combusted at 850 °C in an electrical furnace. About 96 % of each metal was recovered in residual ashes that present a good secondary raw material for copper and nickel production. Low leaching transfers (≤4 %) were observed for copper and nickel from residual ashes leading to the possibility to be landfilled. Therefore, the suggested process can be used as an alternative to the classical technologies for effluent decontamination.     

Fabrication of TiO2 nanoparticles loaded on coal fly ash composite with enhanced photocatalytic activity

By immobilized on the coal fly ashes, the TiO2 nanoparticles photocatalysts were obviously improved in removing organic compounds of the contaminated water. These composite catalysts were fabricated by three different methods involving hydrothermal method, physical blending and sol-gel method. The resulting materials have been characterized by XRD, SEM and FTIR. The photocatalytic activity of these as-prepared samples was assessed by photocatalytic degradation of methylene blue (MB) aqueous solution at ambient temperature under UV-light irradiation. The experimental results indicated that TiO2 nanoparticles were tightly dispersed on the surface of spherical coal fly ash particles, where the adsorption ability of the catalysts is effectively promoted. It was found that the catalysts prepared by hydrothermal method exhibited the highest photocatalytic activity than that prepared by physical blending or sol-gel method which mainly resulted from the synergistic effect of TiO2 nanopartcles and coal fly ashes.     

Extended visible light harvesting and boosted charge carrier dynamics in heterostructured zirconate–FeS<Subscript>2</Subscript> photocatalysts for efficient solar water splitting

Limited visible light absorption, slow charge transference, and high recombination are some of the main problems associated with low efficiency in photocatalytic processes. For these reasons, in the present work, we develope novel zirconate–FeS₂ heterostructured photocatalysts with improved visible light harvesting, effective charge separation and high photocatalytic water splitting performance. Herein, alkali and alkaline earth metal zirconates are prepared by a solid state reaction and coupled to FeS₂ through a simple wet impregnation method. The incorporation of FeS₂ particles induces visible light absorption and electron injection in zirconates, while the appropriate coupling of the semiconductors in the heterostructure allows an enhanced charge separation and suppression of the recombination. The obtained heterostructures exhibit high and stable photocatalytic activity for water splitting under visible light, showing competitive efficiencies among other reported materials. The highest hydrogen evolution rate (4490 µmol g^?1 h^?1) is shown for BaZrO₃–FeS₂ and corresponds to more than 20 times the activity of the bare BaZrO₃. In summary, this work proposes novel visible light active heterostructures for efficient visible light photocatalytic water splitting.     

The Ag-based SPR effect drives effective degradation of organic pollutants by BiOCOOH/AgBr composites

The easy recombination of electron-hole pairs produced by monomeric photocatalysts under light exposure severely limits their application in wastewater treatment. Based on this, BiOCOOH/Ag/AgBr ternary photocatalysts in flower-like microspheres were controllably synthesized by precipitation photoreduction and characterized by various techniques. In addition, the effects of different molar ratio of BiOCOOH and AgBr, catalyst dose, pH and coexisting ions on the photocatalytic degradation of rhodamine B (RhB) and tetracycline (TC) were investigated. The results showed that the BOC/Ag/AgBr-0.5 composite exhibited excellent photocatalytic activity for the degradation of RhB and TC. The excellent photocatalytic activity was mainly attributed to the surface plasmon resonance (SPR) effect of metallic Ag and charge transfer mechanism between composites, thus promoting charge separation. The degradation efficiency of RhB and TC was 92.7% and 72.3% with the degradation rate constant of 0.073 and 0.023 under light irradiation of xenon lamp in 30 and 45 min, respectively, which was 6 and 2 times higher than that of BiOCOOH and AgBr. The stability studies showed that BOC/Ag/AgBr-0.5 maintained a high catalytic activity after four cycles. The results of radical capture experiments showed that h⁺ and ·O₂^– were the main reactive radicals, while ·OH played a secondary role in the photocatalytic system. Subsequently, a potential photocatalytic mechanism was proposed based on the experimental results.     

Pt负载型二氧化钛纳米管/纳米晶复合光催化剂的制备及其光催化性能

结合强吸附能力与高光催化活性的催化剂有望更有效地除去废水中的污染物. 以Degussa P25二氧化钛为原料, 采用水热法制备了二氧化钛纳米管(简称为TNTs), 将TNTs加入到溶有氯铂酸和柠檬酸(还原剂)的无水乙醇中, 在蒸汽相水解装置中通过一步法制备了Pt负载型二氧化钛纳米管/纳米晶复合光催化剂. 蒸汽相处理过程中, 部分纳米管转变为锐钛矿相TiO₂, 仍有部分以管的形式存在, 使纳米复合物保留了较高的吸附能力. 利用X射线衍射(XRD)、透射电子显微镜(TEM)、比表面及孔隙度分析仪等方法对产物进行了表征. 结果表明, 粒径约为4 nm的金属性Pt较好地分散在TNTs及由纳米管转变而来、晶粒尺寸约为8 nm的锐钛矿相TiO₂晶粒表面, 复合物保留了高于216 m²/g的比表面积. 光催化降解染料酸性红及亚甲基蓝的实验结果表明, 纯管有较好的吸附能力, 但是光催化性能非常低, 经120℃蒸气处理并负载贵金属Pt后光催化活性有了显著的提高.     

Hybridized 2D Nanomaterials Toward Highly Efficient Photocatalysis for Degrading Pollutants: Current Status and Future Perspectives

Organic pollutants including industrial dyes and chemicals and agricultural waste have become a major environmental issue in recent years. As an alternative to simple adsorption, photocatalytic decontamination is an efficient and energy‐saving technology to eliminate these pollutants from water environment, utilizing the energy of external light, and unique function of photocatalysts. Having a large specific surface area, numerous active sites, and varied band structures, 2D nanosheets have exhibited promising applications as an efficient photocatalyst for degrading organic pollutants, particularly hybridization with other functional components. The novel hybridization of 2D nanomaterials with various functional species is summarized systematically with emphasis on their enhanced photocatalytic activities and outstanding performances in environmental remediation. First, the mechanism of photocatalytic degradation is given for discussing the advantages/shortcomings of regular 2D materials and identifying the importance of constructing hybrid 2D photocatalysts. An overview of several types of intensively investigated 2D nanomaterials (i.e., graphene, g‐C₃N₄, MoS₂, WO₃, Bi₂O₃, and BiOX) is then given to indicate their hybridized methodologies, synergistic effect, and improved applications in decontamination of organic dyes and other pollutants. Finally, future research directions are rationally suggested based on the current challenges.     

Self-assembly of the Ag deposited ZnO/carbon nanospheres: A resourceful photocatalyst for efficient photocatalytic degradation of methylene blue dye in water

Carbon nanospheres (CNSs) are synthesized by pyrolysis of benzene at 1000?°C. Various UV-light photocatalysts of ZnO/CNSs and Ag-ZnO/CNSs (AZCN) composites are synthesized on the surface of CNSs using a facile chemical precipitation method. Morphological and optical properties of the as-synthesized photocatalysts are characterized by scanning electron microscopy, X-ray diffraction, energy dispersive spectroscopy, UV-Vis spectroscopy, photoluminescence and Raman spectroscopy. Photocatalytic degradation efficiency of methylene blue dye is investigated to examine the photocatalytic activity of synthesized photocatalysts. It is found that as-synthesized ZnO/CNSs composite can degrade higher methylene blue dye (～85.6%) after 25?min of UV irradiation in comparison with that of CNSs. A prominent improvement in the photodegradation is attained by depositing metal (Ag) particles on the surface of ZnO/CNSs composite. AZCN composite displays the enhanced photocatalytic degradation performance (～95% after 15?min of UV light) in high concentration of methylene blue dye. Furthermore, stability performance is studied by recycling the AZCN composite photocatalyst. It is found that the photocatalytic activity of AZCN composite is only slightly decreased even after five cycles. Present work demonstrates that AZCN composite show a great potential in the treatment of organic pollutants for wastewater treatment.     

Photodegradation pathway of rhodamine B with novel Au nanorods @ ZnO microspheres driven by visible light irradiation

A series of Au–ZnO photocatalysts were successfully synthesized from ZnO microspheres impregnated with Au nanorods by the seed-mediated method, and their photocatalytic activity of degradation of rhodamine B (RhB) was investigated. The nanocomposite catalyst exhibited high photocatalytic activity and degraded 92% of RhB solution under visible light irradiation in 330 min. The enhancement of photocatalytic effects was mainly ascribed to the surface plasmon resonance effect of Au nanorods; therefore, Au–ZnO spheres can absorb resonant photons and transfer the electron to the conduction band (CB) of ZnO leading to the separation of electrons and holes under visible light. Meanwhile, the photocatalytic performance was beneficial from the flower-like porous structure of ZnO, which enhances adsorption of the dye molecules and dissolved oxygen on the catalyst surface and facilitates the electron/hole transfer. Furthermore, the degradation pathway was proposed on the basis of the intermediates during the photodegradation process using liquid chromatography analysis coupled with mass spectroscopy (LC–MS). The degradation mechanism of pollutant is ascribed to the superoxide radicals (^·O^2?), which is the main oxidative species for the N-deethylated degradation of RhB. Moreover, the Au–ZnO photocatalysts demonstrated excellent photostability after five cycles. This work provides a facile and effective approach for removal of organic dyes under visible light and thus can be potentially used in the environmental purification.     

Utilization of a ZnS(en)0.5 photocatalyst hybridized with a CdS component for solar energy conversion to hydrogen

Photocatalytic solar energy conversion to chemical energy attracts great attention due to its high potential in harvesting renewable energy for the future. A ZnS(en)_0.5 photocatalyst hybridized with a CdS component was synthesized by solvothermal and precipitation methods to compare the effect of preparation methods on photocatalytic performance. The highest hydrogen production rate (559 μmol g^?1 h^?1) was achieved from a solvothermally synthesized ZnS(en)_0.5?CdS composite at 80 wt% of CdS content under standard 1-sun-irradiation condition (1000 W/m²). Photocatalytic hydrogen production rates from ZnS(en)_0.5?CdS photocatalysts were highly associated with degrees of charge separation, crystallinity, reduction power, and light absorption. By comparing two different routes for the synthesis of ZnS(en)_0.5?CdS photocatalysts, solvothermally-fabricated material was shown to have a higher photocatalytic activity compared with material fabricated by a precipitation method. This improvement may be due to its excellent crystalline and charge-separation characteristics.     

Enhanced photocatalytic activity of BiFeO3 particles by surface decoration with Ag nanoparticles

BiFeO₃ particles with different morphologies and sizes were synthesized via a hydrothermal process, where the morphology and size was tailored by using different KOH concentrations in precursor solution. The samples prepared at n(KOH) = 3, 4.5, 6, and 7.5 M are composed, respectively, of octahedron-shaped particles (500–600 nm), cube-like particles (200–500 nm), irregular spherical agglomerates (9–16 μm) formed from disk-like grains with diameter of 1.4–2.8 μm and thickness of 0.2 μm, and cuboid-shaped particles with length-to-width ratio of 1.4:1–3.5:1 and width size ranging from 80 to 280 nm. Ag nanoparticles were deposited on the surface of BiFeO₃ particles by a chemical reduction method to produce Ag@BiFeO₃ nanocomposites. The photocatalytic activity of prepared samples was evaluated by degrading rhodamine B under simulated sunlight irradiation. It is demonstrated that Ag-decorated BiFeO₃ particles exhibit an enhanced photocatalytic activity compared to bare BiFeO₃ particles. This can be explained by the effective transfer of photogenerated electrons from the conduction band of BiFeO₃ to Ag nanoparticles and hence increased availability of holes for the photocatalytic reaction. Hydroxyl radicals were detected by the photoluminescence technique using terephthalic acid as a probe molecule and are found to be produced over the irradiated BiFeO₃ and Ag@BiFeO₃ photocatalysts; especially, an enhanced yield is observed for the latter.     

Low-temperature processing of thin films based on rutile TiO2 nanoparticles for UV photocatalysis and bacteria inactivation

Using a low-temperature, simple, and economic processing technique, TiO₂ nanoparticles (rutile phase) are immobilized in an inorganic matrix and then deposited on glass for bacteria inactivation in water. Using this low thermal budget method (maximum processing temperature of 220 °C), thin films of immobilized TiO₂ nanoparticles are obtained so that practical water decontamination after UV radiation is possible by avoiding the additional step of catalyst separation from treated water. In order to validate the photocatalytic activities of these TiO₂ nanoparticles (prepared as thin films), they were tested for bacteria inactivation in water under UV–A radiation (λ > 365 nm), while extensive characterizations by dynamic light scattering, X-ray diffraction, ultra violet–visible absorption spectroscopy, fourier-transform infra red spectroscopy, and profilometry were also carried out. Despite previous reports on the low or lack of photocatalytic activity of rutile-phase TiO₂, inactivation of Escherichia coli in water was observed when thin films of this material were used when compared with the application of UV radiation alone. Physical characterization of the films suggests that size and concentration-related effects may allow the existence of photocatalytic activity for rutile-TiO₂ as long as they are exposed under UV–A radiation, whereas no effect on bacteria inactivation was observed for thin films in the absence of TiO₂ or radiation. In brief, a low thermal budget process applied to thin films based on TiO₂ nanoparticles has shown to be useful for bacteria inactivation, while possible application of these films on widely available substrates like polyethylene terephthalate materials is expected.     

新型复合纳米材料用于光催化降解染料废水的研究进展EI北大核心CSCD

光催化技术是解决当今人类社会中环境问题和能源危机两大问题的有效途径,半导体材料在早期的研究中备受青睐。然而,单一半导体光催化剂存在可见光响应程度差、电子空穴对易复合等缺点,光催化技术在降解染料废水的应用中有效率较低,因此研究者对新型复合纳米材料作为光催化剂降解染料废水进行了深入的研究。本文介绍了石墨烯、金属有机骨架、碳量子点三种新型复合纳米材料用于光催化降解染料废水中污染物的研究进展和主要研究结果,按照复合纳米材料设计升级的思路,简述了部分新型复合纳米材料的制备方法,对目标污染物的降解率进行了分析。通过总结新型光催化材料降解水中污染物的性能,对未来发展趋势进行了展望,指出新型复合纳米材料在光催化方向今后的发展趋势和研究重点是有针对性的处理废水,并实现工业化。     

Synthesis and performance of novel magnetically separable nanospheres of titanium dioxide photocatalyst with egg-like structure

A magnetically separable photocatalyst TiO(2)/SiO(2)/NiFe(2)O(4) (TSN) nanosphere with egg-like structure was prepared by a unique process that combined a liquid catalytic phase transformation method, reverse micelle technique and chemical precipitation means. The prepared photocatalyst shows high photocatalytic activity for the degradation of methyl orange in water. The magnetic property measurements indicate that the photocatalyst possesses a superparamagnetic nature. It can be separated from water when an external magnetic field is added and redispersed into water solution after the external magnetic field is eliminated. It is one of the promising photocatalysts for wastewater treatment. A transmission electron microscope (TEM) and an x-ray diffractometer (XRD) were used to characterize the structure of the TSN photocatalyst. The results indicate that nickel ferrite core nanoparticles were completely encapsulated into monodisperse silica nanospheres as carrier, and titania nanoparticle aggregates were coated onto the surface of SN nanospheres, forming an imperfect TiO(2) shell for photocatalysis. The SiO(2) layer between the NiFe(2)O(4) core and the TiO(2) shell effectively prevents the injection of charges from TiO(2) particles to NiFe(2)O(4), which gives rise to an increase in photocatalytic activity. Moreover, the recycled TSN exhibits good repeatability of the photocatalytic activity.     

Biomimetic Photocatalytic System Designed by Spatially Separated Cocatalysts on Z-scheme Heterojunction with Identified Charge-transfer Processes for Boosting Removal of U(VI)

Designing highly efficient photocatalysts with rapid migration of photogenerated charges and surface reaction kinetics for the photocatalytic removal of uranium (U(VI)) from uranium mine wastewater remains a significant challenge. Inspired by natural photosynthesis, a biomimetic photocatalytic system is assembled by designing a novel hollow nanosphere MnO_x@TiO₂@CdS@Au (MTCA) with loading MnO_x and Au nano particles (Au NPs) cocatalysts on the inner and outer surfaces of the TiO₂@CdS. The spatially separated cocatalysts efficiently drive the photogenerated charges to migrate in opposite directions, while the Z-scheme heterogeneous shell further separates the interfacial charges. Theoretical calculation identifies multiple consecutive forward charge transfers without charge recombination within MTCA. Thus, MTCA could efficiently remove 99.61% of U(VI) after 15 min of simulated sunlight irradiation within 3 mmol L⁻¹ NaHCO₃ with 0.231 min⁻¹ of the reduction rate constant, outperforming most previously reported photocatalysts. MTCA further significantly removes 91.83% of U(VI) from the natural uranium mining wastewater under sunlight irradiation. This study provides a novel approach to designing an ideal biomimetic photocatalyst for remediating environmental pollution.     

Preparation of lanthanum-doped TiO<Subscript>2</Subscript> photocatalysts by coprecipitation

The lanthanum-doped TiO₂ (La³⁺-TiO₂) photocatalysts were prepared by coprecipitation and sol–gel methods. Rhodamine B was used as a model chemical in this work to evaluate the photocatalytic activity of the catalyst samples. The optimum catalyst samples were characterized by XRD, N₂ adsorption–desorption measurement, SEM and electron probe microanalyses to find their differences in physical and chemical properties. The experimental results showed that the La³⁺-TiO₂ catalysts prepared by coprecipitation exhibited obviously higher photocatalytic activities as compared with that prepared by the conventional sol–gel process. The optimum photocatalysts prepared by the coprecipitation and sol–gel process have similar adsorption equilibrium constants in Rhodamine B solution and particle size distribution in water medium although there are larger differences in their surface area, morphology and pore size distribution. The pores in the sol-gel prepared catalysts are in the range of mesopores (2–50 nm), whereas the pores in the coprecipitation prepared catalysts consist of bigger mesopores and macropores (>50 nm). The morphology of the primary particles and agglomerates of the La³⁺-TiO₂ catalyst powders was affected by doping processes. The inhibition effect of lanthanum doping on the phase transformation is greater in the coprecipitation process than in the sol–gel process, which could be related with the different amount of Ti–O–La bonds in the precursors. This finding could be used for preparing the anatase La³⁺-TiO₂ catalysts with more regular crystal structure through a higher heat treatment temperature. The optimum amount of lanthanum doping is ca. 1.0 wt.% and the surface atomic ratio of [O]/[Ti] is ca. 2.49 for 1.0 wt.% La³⁺-TiO₂ catalysts prepared by the two processes. The obviously higher photocatalytic activity of the La³⁺-TiO₂ samples prepared by the coprecipitation could be mainly attributed to their more regular anatase structure and more proper surface chemical state of Ti³⁺ species. The optimum preparation conditions are 1.0 wt.% doping amount of lanthanum ions, calcination temperature 800 °C and calcination time 2 h using the coprecipitation process. As compared with the sol-gel process, the coprecipitation process used relatively cheap inorganic raw materials and a simple process without organic solvents. Therefore, the coprecipitation method provides a potential alternative in realizing large scale production.     

Investigation of shape effect of silver nanostructures and governing physical mechanisms on photo-activity: Zinc oxide/silver plasmonic photocatalyst

Plasmonic composites consisting of silver nanostructures and zinc oxide semiconductor have better photocatalytic performance than pure zinc oxide. To prepare the composites, nanostructures of zinc oxide particles, gold spheres, and three different silver morphology including cubes, spheres, and wires were synthesized. A detailed study of the main mechanisms governing the activity of plasmonic photocatalysts showed that the improvement of photocatalytic performance is attributed to localized surface plasmon resonance-mediated energy transfer from silver to zinc oxide. This mechanism, which is performed using non-radiative (near-field) and radiation (far-field) processes, led to an increase in the concentration of e^?/h⁺ pairs near the semiconductor. We also showed that the increase of the photocatalytic activity depends on the shape of the silver nanostructures in the composites. Our theoretical and experimental studies have shown that composites containing silver cubes have the highest increase of photocatalytic activity compared to other morphologies. The percentage of photocatalytic degradation of methylene blue solution in presence of silver cubes was about 15% higher than that of other morphologies. Therefore, by controlling the shape of noble metal nanostructures, the photocatalytic activity of a semiconductor can be maximized and adjusted.     

Fluidized-Bed Bioreactor Applications for Biological Wastewater Treatment: A Review of Research and Developments

Wastewater treatment is a process that is vital to protecting both the environment and human health. At present, the most cost-effective way of treating wastewater is with biological treatment processes such as the activated sludge process, despite their long operating times. However, population increases have created a demand for more efficient means of wastewater treatment. Fluidization has been demonstrated to increase the efficiency of many processes in chemical and biochemical engineering, but it has not been widely used in large-scale wastewater treatment. At the University of Western Ontario, the circulating fluidized-bed bioreactor (CFBBR) was developed for treating wastewater. In this process, carrier particles develop a biofilm composed of bacteria and other microbes. The excellent mixing and mass transfer characteristics inherent to fluidization make this process very effective at treating both municipal and industrial wastewater. Studies of lab- and pilot-scale systems showed that the CFBBR can remove over 90% of the influent organic matter and 80% of the nitrogen, and produces less than one-third as much biological sludge as the activated sludge process. Due to its high efficiency, the CFBBR can also be used to treat wastewaters with high organic solid concentrations, which are more difficult to treat with conventional methods because they require longer residence times; the CFBBR can also be used to reduce the system size and footprint. In addition, it is much better at handling and recovering from dynamic loadings (i.e., varying influent volume and concentrations) than current systems. Overall, the CFBBR has been shown to be a very effective means of treating wastewater, and to be capable of treating larger volumes of wastewater using a smaller reactor volume and a shorter residence time. In addition, its compact design holds potential for more geographically localized and isolated wastewater treatment systems.     

Recent advances in earth-abundant photocatalyst materials for solar H2 production

Harvesting solar energy attracts great attention due to its abundant, clean, and permanent characteristics. Thus, photocatalysts have emerged as promising candidates for converting the solar energy to practically useful hydrogen molecules. Tremendous efforts have been devoted in developments of efficient photocatalysts for water splitting, but most of photocatalysts utilize noble metals to improve photocatalytic performance. Progress in photocatalyst materials for the hydrogen production coupled with a better understanding of the basic catalytic mechanisms has enabled better selection of catalytic nanomaterials with improved performance. In this review, we analyze the current state of the art in photocatalyst materials for photochemical hydrogen production through water splitting using earth-abundant materials. We also explore two main factors involved in both material morphology and sacrificial agent to further improve the activity, efficiency and stability of photocatalysts.     

Hydrothermal synthesis of nanostructured TiO2 particles and characterization of their photocatalytic antimicrobial activity

Nanostructured titania particles were synthesized by using hydrothermal processing and the photocatalytic antimicrobial activities were characterized. Both sol-gel synthesized and commercial TiO2 (anatase) samples were processed with two step hydrothermal treatments, under alkaline and neutral conditions. Scanning Electron Microscope (SEM) images showed that alkaline treatment yields nanofibers and lamellar structured particles from the commercial anatase and sol-gel synthesized samples respectively. Further treatment of nanofibers and nanostructured lamellar particles with distilled water results with crystal growth and the formation of nano structured bipyramidal crystalline particles. The photocatalytic antimicrobial activities of the samples were determined against Escherichia coil under irradiation. It was observed that the samples treated under alkaline conditions have improved activity than the original anatase samples. Limited activity and resulting time lag in bacterial inactivation were observed for hydrothermally treated samples with distilled water. However, a post treatment comprising the UV irradiation in aqueous conditions enhanced the photocatalytic activity.     

Photocatalytic activity of β-MnO2 nanotubes grown on PET fibre under visible light irradiation

Development of visible light response semiconductor photocatalysts in degradation of organic compounds (pollutants) is one of the current research focuses due to the severe environmental pollution from various industrial and agricultural pollutants in water bodies. In this work, β-MnO₂ particles were successfully prepared by sol-gel method with potassium permanganate and manganese (II) sulphate as precursors. The transmission electron microscope/selected area electron diffraction analysis indicates that the particles were polycrystals with tubular structure. The photodegradation of Rhodamine B (RhB) solution using β-MnO₂ nanotubes under visible irradiation followed 1^st order kinetic with rate constant of 0.022 ± 0.003 min^?1 and photodegradation efficiency of 90.3% after 120 min under visible light irradiation. The N-deethylation was the dominant process in photodegradation of RhB dye by β-MnO₂ nanotubes as compared to cycloreversion process. By applying similar synthesis condition, the β-MnO₂ nanotubes were successfully synthesised on PET fibre. The photodegradation efficiency of RhB dye under circulation condition by β-MnO₂ nanotubes grown on PET fibre under visible light irradiation was 1.23 h^?1. The result suggests that β-MnO₂ nanotubes grown on PET fibre could be used as visible light-driven photocatalysts for wastewater purifier application.