Purification Of Polluted Water Research Articles

Research Advances in Wood Composites in Applications of Industrial Wastewater Purification and Solar-Driven Seawater Desalination.

In recent years, the ecosystem has been seriously affected by sewage discharge and oil spill accidents. A series of issues (such as the continuous pollution of the ecological environment and the imminent exhaustion of freshwater resources) are becoming more and more unmanageable, resulting in a crisis of water quality and quantity. Therefore, studies on industrial wastewater purification and solar-driven seawater desalination based on wood composites have been widely considered as an important development direction. This paper comprehensively analyzes and summarizes the applications of wood composites in the fields of solar-driven seawater desalination and polluted water purification. In particular, the present situation of industrial wastewater containing heavy metal ions, microorganisms, aromatic dyes and oil stains and related problems of solar-driven seawater desalination are comprehensively analyzed and summarized. Generally, functional nanomaterials are loaded into the wood cell wall, from which lignin and hemicellulose are selectively removed. Alternatively, functional groups are modified on the basis of the molecular structure of the wood microchannels. Due to its three-dimensional (3D) pore structure and low thermal conductivity, wood is an ideal substrate material for industrial wastewater purification and solar-driven seawater desalination. Based on the study of objective conditions such as the preparation process, modification method and selection of photothermal conversion materials, the performances of the wood composites in filtration, adsorption and seawater desalination are analyzed in detail. In addition, this work points out the problems and possible solutions in applying wood composites to industrial wastewater purification and solar-driven seawater desalination.

Wastewater Treatment by Improving the Local Clay Capacity with Chemical and Thermal Activation

Worldwide, liquid effluents are generally discharged into the environment untreated, which, in turn, are affecting humans, animals and plants. Preserving our environment is a priority, especially with the emergence of epidemics in recent years. As a part of our investigation, we aim to treat the wastewater of the Ouargla region by enhancing the adsorption capacity of local clay collected from El-Oued (Elmghaier, south of Algeria) using thermo-chemical activation for the removal of organic pollutants. The clay used was (illite, kaolinite, and quartz 62.0%, 27.0% and 11.1%, respectively). The experiments proved the efficiency of enhancing the adsorption capacity of local clay by thermo-chemical activation in the treatment of urban wastewater to determine the efficiency by the following characteristics: chemical oxygen demand, biochemical oxygen demand, total suspended solids, and turbidity, respectively. Acid-activated clay with sulphuric acid achieved high efficiency on polluted water purification at the ideal concentration (0.75 N) and an adsorption rate of (80.16%, 90.74%, 93.33% and 90.74%), while the result decreased in the optimal concentration of acid activated clay HCl (0.134 N) and the adsorption rate was 73%, 60.92%, 94.31% and 65.57%. The thermal activation effect of the clay studied under optimal temperature conditions (400°C) shows that the adsorption ratio increased with higher temperatures (82%, 65%, 89.56% and 78.65%).

A novel amino-functionalized magnetic silica cryogel to rapidly capture and eliminate Cr(VI): Its efficient performance and synergetic mechanism

Although silica (SiO2) cryogel possesses high surface area and physicochemical stability, the poor performance, high production cost, and difficult separation limit its capability to efficiently remove Cr(VI) from water. To address this issue, commercial water glass was chosen as the silica source, and Fe3O4 was used as the core to synthesize the magnetic SiO2 cryogel, which was then anchored with 3-(2-Aminoethylamino)propyltrimethoxysilane (APTMS) to prepare a novel cryogel named Fe3O4 @SiO2-APTMS. Successful amino functionalization was evidenced by the characterization of techniques such as SEM, TEM, FTIR, XRD, VSM, and BET. The adsorption performance of Fe3O4 @SiO2-APTMS was evaluated systematically under different conditions concerning the initial solution pH, adsorbent dosage, temperature, and coexisting anions and cations. Adsorption kinetics, isotherms, and thermodynamics revealed that the pseudo-second-order kinetic, Langmuir models preferably fitted the adsorption data, suggesting a single-layer, chemical sorption, and exothermic adsorption process occurred. The Fe3O4 @SiO2-APTMS exhibited a fast adsorption rate to Cr(VI) ions that it reached the equilibrium within 10 min when the initial Cr(VI) concentration was less than 200 mg/L, and the theoretical maximum capacity was estimated as high as 240.96 mg/g at 298 K and pH 2.0, which are superior than the majority magnetic adsorbents. Moreover, the amino-modified magnetic cryogel could be rapidly separated by the external magnetic field and maintain effective Cr(VI) removal efficiency even after 4 cycles. It was further expounded that the outstanding Cr(VI) removal performance could be attributable to electrostatic attraction coupled with reduction and chelation. The study could provide a promising alternative material for the Cr(VI)-polluted water purification and highlight the potential application of related magnetic cryogel material. The findings also implied the amino-decorated material could participate in the redox of Cr(VI) at nearly one-half of the total amount for the detoxification.

Architecting Hybrid Donor–Acceptor Dendritic Nanosheets Based on Polyoxometalate and Porphyrin for High‐Yield Solar Water Purification

AbstractHarvesting solar energy for saline and polluted water purification is a sustainable and affordable solution to alleviate the stress on water shortages. However, the water evaporation rate relies on high optical intensity and suffers from inadequate energy conversion. Herein, a novel hybrid donor–acceptor dendritic nanosheets (denoted as DNS) composed of phosphomolybdic acid (PMA) clusters and porphyrin ligands is reported. Experimental results and molecular dynamics simulations indicate that the PMA and porphyrin are oriented attachment and assembled into a stable nanostructure. Benefiting from the advantages of the unique structure and photosensitive components, the DNS exhibits high evaporation rate of 2.23 kg m‐2 h‐1 with 90.9% energy efficiency under 1 sun irradiation. It is noteworthy that the evaporation performance is upgraded by innovative technology, and even under 0.5 sun that is close to the natural sunlight intensity, the evaporation rate reaches up to 1.31 kg m‐2 h‐1, which exceeds that of the vast majority of the reported evaporators. Furthermore, this evaporator also displays excellent seawater desalination and wastewater decontamination based on photo‐thermal distillation, highlighting its potential application toward water purification.

Zirconium hydroxide nanoparticle encapsulated magnetic biochar composite derived from rice residue: Application for As(III) and As(V) polluted water purification

Finding a low-cost and suitable adsorbent is still in urgent need for efficient decontamination of As(III) and As(V) elements from the polluted waters. A novel zirconium hydroxide nanoparticle encapsulated magnetic biochar composite (ZBC) derived from rice residue was synthesized for the adsorptive capture of As(III) and As(V) from aqueous solutions. The results revealed that ZBC showed an acceptable magnet separation ability and its surface was encapsulated with lots of hydrous zirconium oxide nanoparticles. Compared to As(III), the adsorption of As(V) onto ZBC was mainly dependent on the pH of the solution. The intraparticle diffusion model described the adsorption process. ZBC showed satisfactory adsorption performances to As(III) and As(V) with the highest adsorption quantity of 107.6 mg/g and 40.8 mg/g at pH 6.5 and 8.5, respectively. The adsorption of As(III) and As(V) on ZBC was almost impervious with the ionic strength while the presence of coexisting ions, especially phosphate, significantly affected the adsorption process. The processes of complexation reaction and electrostatic attraction contributed to the adsorption of As(III) and As(V) onto ZBC. ZBC prepared from kitchen rice residue was found to be a low cost environmentally friendly promising adsorbent with high removal capacity for As(III) and As(V) and could be recycled easily from contaminated waters.

Waste-to-resources: Green preparation of magnetic biogas residues-based biochar for effective heavy metal removals

The agricultural wastes disposal and polluted water purification are always the key issues of environmental restoration. In this work, a magnetic biogas residue-based biochar (mBR-C) by direct pyrolysis and sonochemical method was prepared from biogas residue (BR). Response design methodology based on Box-Behnken design was used for the preparation parameters optimization. The characterization results identified that mBR-C had well-developed pore structure and surface area, which was beneficial to diffuse and capture heavy metal ions. Traces of toxic heavy metal in mBR-C was leached (˂0.04 mg/L) through TCLP method, indicating the environmental safety of the magnetic biochar. Meanwhile, the mBR-C exhibited excellent solid-liquid separation efficiency because of its strong magnetism. The series of adsorption experiments indicated that mBR-C could capture Cu2+ and Pb2+ rapidly, and the maximum adsorption capacity for Cu2+ and Pb2+ was 75.76 and 181.82 mg/g, respectively, which was higher than some other biochars previously reported. mBR-C was further applied in the synthetic wastewater treatment, which could effectively purify at least 600 mL (150 BV) to meet emission standards. After several column adsorption-desorption cycles, the adsorption capacity could still reach 85%, implying that mBR-C has good reusability and stability. Overall, the mBR-C can be used as an eco-friendly, desirable, economic and recyclable biosorbent in heavy metal polluted water treatment, providing a new idea for a combination of biogas residue recycle and wastewater treatment.

Al cluster oxide modified a hematite/P3HT ternary Z-scheme photocatalyst with excellent photocatalytic performance: A discussion of the mechanism

The Z-scheme photocatalyst is valuable for use in polluted water purification, and there is a need to develop a cheap and efficient photocatalyst. This study presents a new type of Z-scheme photocatalytic material composed of hematite and P3HT, also, the Al cluster oxides were first used as a charge transfer mediator to construct Z-scheme photocatalysis system. In addition, by analyzing the electron rearrangement phenomenon exhibited by the XPS spectrum and the experimental results of the in-situ illumination XPS, it is found that Al cluster is beneficial to the electron multi-step charge transfer process and Al cluster favors the construction of Z-scheme structure between hematite and P3HT. This Poly-3-hexylthiophene (P3HT)/Al cluster oxide/hematite ternary photocatalyst exhibited an excellent degradation effect on bisphenol A and tetracycline. This study demonstrates the feasibility of using the Al cluster as a charge mediator in the Z-scheme, providing new Z-scheme catalyst construction idea which is beneficial to the popularization and use of Z-scheme system in practical applications, and providing a new material for water pollution purification.

A novel immobilized Z-scheme P3HT/α-Fe2O3 photocatalyst array: Study on the excellent photocatalytic performance and photocatalytic mechanism

The Z-scheme photocatalyst is valuable for use in polluted water purification. To improve the practical application value of the Z-scheme, in this study, a nano α-Fe2O3 and P3HT composite photocatalyst array was synthesized by electrophoretic deposition for the first time. This material was named F1P. The EPR, VBXPS and in situ illumination XPS analyses indicated that the charge transfer path of F1P conforms to the Z-scheme, and F1P array has a high light energy conversion efficiency. Due to the advantages of the Z-scheme system and the good light harvesting ability, F1P exhibited a good degradation effect on different types of pollutants under visible light irradiation. The degradation efficiency of tetracycline and bisphenol A by F1P can reach 97 % and 99 %, respectively. Moreover, F1P showed a certain resistance to water quality changes. After four cycles, F1P can maintain the structural stability and good pollutant treatment effect. Due to the high redox ability of F1P, the complex structure of pollutants can be destroyed and the degradation path of pollutants in F1P system was also analyzed. This study provides a new way of synthesizing Z-scheme systems and immobilizing Z-scheme photocatalysts. F1P is a new material with high practicability.

Solid waste and graphite derived solar steam generator for highly-efficient and cost-effective water purification

Utilizing the clean and renewable solar energy to generate steam for wastewater purification or seawater desalination is a promising solution to the worldwide scarcity of fresh water. Herein, we report a highly-efficient, eco-friendly and cost-effective solar steam generator based on ball-milling graphite and cellulose fiber from waste paper. Ball-milling graphite/cellulose fiber composite aerogels are facilely developed via a freeze casting-drying method, endowing a featured vertically aligned porous structure. The fabrication of composite aerogels and the construction of evaporation systems take full advantages of recycled materials, contributing to the low cost and solid waste reclamation. High porosity, strong solar absorption, hydrophilicity and low thermal conductivity of the composite aerogels collectively contribute to a splendid solar evaporation rate of water as high as 1.61 kg m−2 h−1, with photothermal efficiency of ~90% under one sun illumination (1 kW m−2). Quantitative studies reveal the effects of ball-milling graphite/cellulose fiber ratio, ball-milling graphite concentration and thickness of composite aerogels on the solar evaporation rates, suggesting the optimal design of composite aerogels. Furthermore, the cycling stability and the capability for seawater desalination as well as polluted water purification manifest the potential of the composite aerogels to purify diverse water. Outdoor tests show 8–13 L of fresh water could be produced daily by 1 m2 of composite aerogel.

Efficient Interfacial Solar Steam Generator with Controlled Macromorphology Derived from Flour via “Dough Figurine” Technology

A solar‐driven interface steam generator (SISG) has potential applications in saline water desalination and polluted water purification. A shape‐ and size‐controlled, low‐cost, eco‐friendly solar‐absorber material is urgently desired for practical applications of SISGs. Herein, a facile, sustainable, and scalable approach is proposed to produce tailored SISGs with controlled macromorphology derived from flour via “dough figurine” technology originating from the China Han Dynasty. Three kinds of self‐floated flour‐based absorbers, i.e., near‐cylindrical (integrated), near‐spherical (loose packing), and powdery (dense packing) absorber used as SISGs, are discussed. More importantly, it is found that the macromorphology significantly influences water transport and interfacial thermal management of SISGs; thus the integrated absorber has an obvious advantage over the other two absorbers, which possesses a high evaporation efficiency of 71.9% at normal solar illumination. The proposed “dough figurine” technology breaks the limitations of the inherent geometry of reported biomass‐based SISGs, which provides an important guidance for SISG use in remote and impoverished areas.

Photoluminescence and photo-catalytic properties of Zn1−x−yCuxMnyS nanostructures

Zn1−x−yCuxMnyS [(0 ≤ x ≤ 0.1), (0 ≤ y ≤ 0.1)] nanostructures have been synthesized by facile chemical co-precipitation technique at room temperature. Crystallographic, topographical and morphological characterization of synthesized nanomaterials have been done by X-ray diffraction, Scanning Electron Microscope and Transmission Electron Microscope, respectively. Synthesized nanoparticles crystallizes in zinc blende structure having average crystallite size nearly 2–3 nm. Comparison of the diffraction and electron microscopy studies reveal the formation of single nanocrystals. The energy dispersive X-ray spectroscopy and Fourier transform infrared spectroscopic studies have been carried for the detailed quantitative and qualitative analysis of synthesized nanostructures. Optical characterization of synthesized nanomaterials has been done by UV–visible absorption and steady state photoluminescence spectroscopic studies. The room temperature energy resolved photoluminescence (PL) spectra show multi-chromatic emissions originating from the host and dopant related defect states. The photo-catalytic activity of synthesized nanomaterials under UV irradiation have been tested using methylene blue (MB) dye as test contaminant in aqueous media. Photo-physical and photo-chemical behaviour dependence on doping concentration has been thoroughly studied to explore the potential of synthesized nanomaterials for next era opto-electronic industrial applications as well as polluted water purification.

Photo-Catalytic Activity of Ca<sub>1-x</sub>Ni<sub>x</sub>S Nanocrystals

Ca1-xNixS (0 ≤ x ≤ 0.05) nanocrystals have been synthesized by facile solid state reaction method. Synthesized nanocrystals are further etched with mild acid solutions to reduce the particle size, which augments the surface to volume ratio and confinement of carriers. Crystallographic and morphological characterizations of synthesized nanomaterials have been done by X-ray diffraction and electron microscopy, respectively. Comparison of the diffraction and electron microscopy studies reveal the formation of single crystalline nanostructures. Optical characterization of synthesized nanomaterials has been done by UV-vis. absorption spectroscopic studies. The photo-catalytic activity of synthesized nanomaterials under UV irradiation has been tested using methylene blue (MB) dye as a test contaminant in aqueous media. Photo-catalytic behaviour dependence on dopant concentration and etching has been thoroughly studied to explore the potential of synthesized nanomaterials for next era optoelectronic industrial applications as well as polluted water purification.

English

 Abstract— Our nature and natural resources are the real teachers of our engineers. In wastewater engineering, one of the most sophisticated methods of wastewater treatment is the tertiary treatment or biological treatment. Methods such as biodisc, biofiltration and activated sludge use tiny organisms to remove organic and inorganic pollutants from wastewater. Other higher levels of organisms, such as plants, have been also used for polluted water purification. In phytoremediation, with its different methods of purification, plants are used to remove pollutants from wastewater. Other organisms such as algae, shellfish and fish can be also applied for wastewater treatment. In this paper, the results of the research on using organisms to remove pollutants such as heavy metals from different kinds of wastewaters are presented. The researches were either based on the measurements on nature, or pilot studies in the laboratory. We used water hyacinth to remove nitrate, phosphate, BOD5 and COD from municipal wastewater. The common reed and some other aquatic plants were used for the purification of wastewaters discharged from oil industries and gas purification factories. The concentrations of metals were measured in tissues of organisms exposed to polluted waters in nature; organisms such as algae, fish, shellfish, plants and worms. High concentrations of metals were observed in the organism tissues, suggesting they are favorable for wastewater treatment. The results suggest that a combination of methods would be the most appropriate and in most cases economic method for the treatment of different types of wastewater.

Theoretical and experimental study of the processes of water purification in a biofilter

This paper presents the results of experimental measurements of substrate concentrations characterizing the efficiency of polluted water purification by a drop biofilter. A model describing the process of purification based on the diffusion-kinetic approach is presented. A good agreement between the experimental and theoretically calculated characteristics of the purification process has been shown. A simple semiempirical relation for estimating the operation of the drop biofilter is given.

Séparation d'insolubles en phase liquide par électroflottation

Generally speaking, flotation relies on surface and interface tension properties to get solid particles to hook on to gas bubbles produced in a liquid. Conventional flotation methods (e.g. ore beneficiation) result in average enrichment in terms of a given constituent towards the surface, whereas the aim of polluted water treatment is to extract large quantities of fine matter after initial coarse separation. Mechanically-produced gas bubbles are too big for really effective results, but sizes as small as 0.2 mm can be produced by electrolysis, this being the limit for laminar rising flow. The most rational industrial system is one with the polluted liquid and bubble flows in opposite directions which gives the best concentration gradients and highest interception probability. The liquid passes through electrodes arranged in sheets at the bottom of the tank and the sludge is removed from the surface by mechanical means. The liquid flow velocity limit is about 4 m/h ; specific current and voltage are 100 A/m2 and 8-10 V ; the bubbles are swept over an effective depth of 0.5-1.0 m. The liquid can be prepared before treatment if required, for example by flocculation, which sometimes makes treatment more effective. The main advantages of the process are that it is very effective, easy to regulate, requires little room, gives a high sludge concentration, is economical to run and has simple conditioning requirements. For example, paper mill effluent at 1 g/l has been treated sucessfully with an input of 140 Wh/m3 without conditioning and 60 Wh/hm3) after flocculation. Residual solids in the water after treatment were less than 10 mg/l in the first case, and there were none in the second. The process is suitable for any raw or polluted water purification application and thus offers an exceptionally wide scope.