Treatment Of Contaminated Wastewater Research Articles

Periodate activation with copper oxide nanomaterials for the degradation of ciprofloxacin - A new insight into the efficiency and mechanisms

In this study, CuO was synthesized using a facile precipitation method and was characterized using various techniques for the efficient activation of periodate (PI). Compared to systems consisting of PI alone (0.5 mM) and CuO alone (0.5 g/L), the CuO (0.5 g/L)/PI (0.5 mM) process exhibited improved degradation performance for ciprofloxacin (CIP), a widely used refractory antibacterial drug, with 98% of this pollutant (20 mg/L) removed in a reaction time of 30 min. Both radical and nonradical degradation pathways were identified to play a significant role in the developed CuO/PI system, where the nonradical pathway (holes and electrons) played the most important role in the degradation of CIP. Under both acidic (pH = 3) and near-neutral (pH = 6) conditions, the system showed an improved efficiency for the degradation of CIP in comparison with alkaline conditions (pH = 10). This was attributed to a more facile adsorption of the PI ions onto the surface of the CuO nanoparticles, induced by the electrostatic attraction between the PI ions and the CuO nanomaterial. Analysis of the degraded samples with ultrahigh-performance liquid chromatography quadrupole time-of-flight mass spectrometry (UHPLC Q-TOF MS) demonstrated that cleavage of the piperazine ring and defluorination were the primary degradation pathways of CIP under this oxidation process. The CuO/PI system also showed an excellent removal efficiency for other refractory organic contaminants, such as sulfamethoxazole (SMX) and methylene blue (MB), in various water matrices, including real wastewater. Moreover, respiration tests revealed that the toxicity of the effluents was reduced after the treatment process. In conclusion, this research presents a novel, promising periodate activation technique for the removal of refractory organic contaminants in wastewater treatment.

Fabrication of robust ceramic supported polymeric composite nanofiltration membrane for heavy metal contaminated wastewater treatment

Nanofiltration (NF) membranes with positive charge are essential for efficient removal of heavy metals and salts from waste water. In this work surface modified positively charged novel ‘ceramic-supported-polymeric’ (CSP) composite NF membranes were fabricated with the copper ions embedded crosslinked polyethyleneimine polymer matrix over tubular ceramic substrate using facile dipcoating method. EDX, ATR-FTIR, XPS, FESEM, AFM and contact angle analyses were performed to characterize the chemical structures and morphologies of the prepared membranes. The composite NF membrane exhibited satisfactory pure water permeability (PWP) of 8.1 L.m−2.h−1.bar−1 and promising salt (87.19 % and 74.41 % for Mg2+ and Ca2+, respectively) and heavy metal ion rejections (91.73 %, 83.15 % and 75.50 % for Zn2+, Ni2+ and Cd2+, respectively). Activation energy and overall size-exclusion-dehydration phenomena along with steric hindrance and Donnan electrostatic exclusion plays an important role for heavy metals and salts rejection. In addition, the membrane showed excellent antifouling properties (>99 % humic acid removal) with high flux recovery ratio (77.6 %) and low flux decline ratio (33 %) for 5 h operations (3rd cycle) together with outstanding antibiofouling ability towards Brevibacillusagri and Leclerciaadecarboxylata. Furthermore, excellent chemical stability of the membrane suggests its potential application for waste water treatment under critical conditions.

A versatile nanocomposite Fe0@SiO2@CaO2 for reductive, oxidative, and coagulation removal of organic and inorganic contaminants from water

Water scarcity is one of the most pressing global challenges and limits economic and social development. Multiple processes of current technologies for water purification are needed to meet water quality objectives due to their contaminant-specific removal capability. Here, we developed Fe0@SiO2@CaO2 nanocomposite with three layers of core–shell structure that could achieve an array of water contaminants removal by oxidation, reduction, and flocculation. >99 % of 50 mg/L tetracycline, 20 mg/L pentachlorophenol, 450 mg/L Cd(Ⅱ), 20 mg/L Cr(Ⅵ), or 80 mg/L P (in form of PO43−) was removed by 2 g/L Fe0@SiO2@CaO2 in 24 h. Moreover, Fe0@SiO2@CaO2 (2 g/L) showed an excellent performance in turbidity removal (239 mg/L kaolinite suspension, removal rate > 99 %) and water decolorization (50 mg/L humic acid, removal rate > 93 %). Cd(II) and Cr(VI) could be reduced to Cd(0) and Cr(III), respectively, through electronic reduction reactions using Fe0 and •H, which is formed during the reaction Fe0 + 2H+→2•H + Fe2+; Cd(Ⅱ) and the formed Cr(III) could coprecipitate with the formed orthosilicic acid and OH−. The removal of P was mainly resulted from the coordination with released Ca2+ and iron compounds. Charge neutralization by nanocomposite and coagulation with the products from nanocomposite transformation were responsible for the kaolinite removal. Reduction by •H and Fe0, oxidation by •OH derived from the Fenton reaction, and/or coagulation accounted for the organic contaminant removal. This work provides a novel material that can be used to simultaneously remove a range of contaminants in wastewater treatment.

Synchronous pyrolysis and activation of poly (ethylene terephthalate) for the generation of activated carbon for dye contaminated wastewater treatment

To address the increasing accumulation of water bottle waste and lack of effective recycling processes, water bottle waste was upcycled into a high value activated carbon product. This growing waste feedstock has proved to be a promising precursor for activated carbon, but it has not been investigated for use in the treatment of dye-contaminated effluent which is a very high-volume source of waste from textile industries. In this work, the production of activated carbon from water bottle waste by chemical activation using KOH was optimized and validated for the application as an adsorbent of textile dyes. The activation conditions of 800 °C for 1 h proved to be most optimal based on conversion efficiency, surface area, surface charge, and yield measurement. It was found that the product’s negative zeta potential (−40 mV) and high surface area (1124 m2/g), provided excellent adsorption capacity for the cationic methylene blue dye (335 mg/g). The adsorption of this representative dye was studied in detail and compared with cationic brilliant green dye and a mixture containing anionic methyl orange dye. Although the adsorption was found to depend on dye charge characteristics, there is potential for adsorption enhancement through pH adjustments. Additionally, the AC demonstrated the ability to treat mixed dye wastes containing anionic dyes despite its selective adsorption towards cationic dyes of over twice the amount. Overall, the product showed potential to be extended to a variety of textile dyes to provide excellent value for the textile industry while also helping to divert a significant amount of waste from landfills.

Efficient promotion of Cr(VI) removal over Bi2S3 nanoparticles with cupric ions: Potential applications in electroplating wastewater and contaminated groundwater

Emerging Bi2S3-based nanotechnology has great potential in Cr(VI)-contaminated wastewater treatment. In this work, it was found for the first time that Bi2S3 nanoparticles (BS-D) prepared from dual sulfur sources of L-cysteine and ammonium sulfide efficiently promoted Cr(VI) removal with excellent selectivity for simultaneous removal of Cr(VI) and Cu2+ from aqueous solutions containing various co-existing ions (including Na+, K+, Ca2+, Zn2+, Ni2+, Cd2+, NO3–, SO42− and Cl−) at pH > 3, preferably at pH of 4.5. Besides, BS-D had stable performance for co-removal of Cr(VI) and Cu2+ in five recycling tests. Kinetic and thermodynamic studies indicated that the adsorption of Cr(VI) or Cu2+ by BS-D was a spontaneous endothermic process and conformed to pseudo-second-order kinetic model. The adsorbed Cr(VI) ions were partially reduced to Cr(III), which were leached into the solution at pH ≤ 3, inhibiting the adsorption of Cu2+ on BS-D and its promotional effect on Cr(VI) removal by BS-D. The mutual promotional effects between Cu2+ and Cr(VI) during their co-removal by BS-D were ascribed to electrostatic attraction between HCrO4− and Cu2+ and smaller pH variation in mixed Cr(VI)-Cu2+ solutions. Finally, potential applications of BS-D were demonstrated by co-removal of Cr(VI) and Cu2+ from real electroplating wastewater and contaminated groundwater. This work provided a promising BS-D adsorbent for Cr(VI)-contaminated wastewater treatment, and shed insight on the influence of Cu2+ on the Cr(VI) removal by BS-D.

Influence of C/N ratios on treatment performance and biomass production during co-culture of microalgae and activated sludge.

Novel phycosphere associated bacteria processes are being regarded as a potential and cost-effective strategy for controlling anthropogenic contaminants in wastewater treatment. However, the underlying concern with the process is its vulnerability to improper organic or nutrient intake. This study established a synergistic interaction between microalgae and activated sludge in a three-photobioreactor system (without external aeration) to understand how pollutants could be mitigated whilst simultaneously yielding biomass under different C/N ratios of 1:1, 5:1 and 10:1. The result showed that the superior biomass productivity was facilitated at a C/N ratio of 5:1 (106 mg L-1 d-1), and the high degradation rate constants (kCOD = 0.25 d-1, kTN = 0.29 d-1, kTP = 0.35 d-1) was approximated using a first-order kinetic model. The removal of pollutants was remarkably high, exceeding 90% (COD), 93% (TN), and 96% (TP). Nevertheless, the C/N ratio of 1:1 resulted in a threefold drop in biomass-specific growth rate (μ = 0.07 d-1). Microalgal assimilation, followed by bacterial denitrification, is the major pathway of removing total nitrogen when the C/N ratio exceeds 5:1. Activated sludge plays an important role in improving microalgae tolerance to high concentration of ammonia nitrogen and boosting nitrification (light phase) and denitrification (dark phase). The use of phycosphere associated bacteria could be a promising strategy for controlling nutrients pollution and other environmental considerations in wastewater.

Enhanced photodegradation toward graphene–based MgFe2O4–TiO2: Investigation and optimization

In this work, graphene–based MgFe2O4–TiO2 (MFO–TiO2@rGO) nanocomposite was synthesized and conducted an efficient photo–treatment with p–nitrophenol (PNP) as a well–known pollutant in water. The ternary material was characterized by modern analysis methods including Fourier transform infrared spectroscopy, X–ray diffraction, Raman spectroscopy, Transmission electron microscopy, Energy–dispersive X–ray spectroscopy, Selected area electron diffraction, and UV–vis spectroscopy. The simultaneous effects of the volume of H2O2, catalyst dosage, and pH on the photodegradation of p–nitrophenol were also examined by full factorial experimental design according to Box–Behnken designs. As a result, the characterization has confirmed the uniform bounding of MFO and TiO2 nanosizing from 4 to 6 nm on graphene with a high crystallinity degree. The photocatalysis of this material toward PNP can reach up to ∼99.44% in only 60 min reaction under UV control with 1.12 mL H2O2 added, 38.15 mg catalyst, and pH 9. Besides, in solar condition (directly under sun), the material also expressed a relatively impressive capability in degrade PNP from water. Furthermore, the ternary nanocomposite can be easily recycled and reused with an inconsiderable change in yield, represented by the elimination yield of recovered MFO–TiO2@rGO was significantly more than 90% after ten–run cycles. Indeed, the nanocomposite suggests an efficient pathway for treating organic contaminants in wastewater treatment.

Facile synthesis of hierarchical Ti3C2@FeOOH nanocomposites for antimony contaminated wastewater treatment: Performance, mechanisms, reutilization, and sustainability

Designing well-behaved nanocomposites for adsorbing and removing heavy metals has been the top strategies in wastewater treatment. Herein, we report a MXene-based hierarchical nanocomposite via in-situ growth of ferric oxides (FeOOH) on the alkali Ti3C2 for efficient immobilization of Sb(III) and Sb(V) from aqueous solution. The alkalized MXene with negatively charged surface allows the formation of stable heterojunction structure between Ti3C2 and FeOOH through electrostatic self-assembly, resulting in uniformly distributed FeOOH nanoparticles onto Ti3C2 nanosheets. The Ti3C2@FeOOH nanocomposite exhibits maximum adsorption capacities at 111.50 and 93.22 mg/g for Sb(III) and Sb(V), respectively, outperforming majority of metallic-based adsorbents. DFT calculations reveal that the binding energy between Ti3C2@FeOOH and Sb(III) is higher than that of Sb(V), which agree well with the experimental results. The combination of inner-sphere complexation and electrostatic attraction are the dominant forces responsible for the removal of Sb species according to microanalysis. Moreover, the as-prepared nanocomposite presents potential applications in treating antimony contaminated wastewater with high reusability and sustainability. Interestingly, the Ti3C2@FeOOH after loading with Sb species can serve as potential electrode materials, thereby minimizing secondary pollution of waste adsorbents to the environment. This work opens new avenues for function tailoring of nano-multilayered composites towards remediation of heavy metals from water media.

Hydrothermal synthesis of titanium dioxide/graphene aerogel for photodegradation of methylene blue in aqueous solution

Titanium dioxide/graphene aerogel (TiO 2 /GA) was synthesized via a one-pot hydrothermal method and characterized by various spectroscopic techniques, including X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscope, transmission electron microscopy, Raman spectroscopy, and UV-Vis spectroscopy. The influences of pH and TiO 2 /GA dose on the photocatalytic performance were investigated against positive dye methylene blue (MB) under UV light control. The characterization of TiO 2 /GA revealed that the synthesized TiO 2 nanosize of 12–22.5 nm was uniformly distributed onto the graphene layers. The bandgap of the as-prepared nanocomposite was 2.63 eV, lower than that of pure TiO 2 (3.2 eV). The kinetic studies exhibited that the adsorption–desorption equilibrium was achieved after 60 min following the pseudo-second-order. Meanwhile, 99.9% of MB was eliminated after 120 min at pH 9 with a 20 mg catalyst. The degradation data were well fitted to the pseudo-first-order kinetic model. Accordingly, applying TiO 2 /GA as an efficient photocatalyst indicates a potential pathway for the degradation of organic contaminants in wastewater treatment.

Kinetics and thermodynamics of Cr (VI) reduction by Tamarindus indica methanol leaves extract under optimized reaction conditions

Environmental contamination with Cr (VI) has recently attracted public attention because of its high concentration in soil and wastewater originating majorly from anthropogenic activities and natural processes. Reduction of Cr (VI) to Cr (III) is a feasible method for minimizing chromium pollution. This work aimed at characterizing the effects of Cr (VI) reduction conditions in a batch experiment such as temperature, hydrogen ion concentration, time, and reactant concentrations, as well as kinetics and thermodynamics of the reaction using Tamarindus indica methanol leaves extract as a reductant. Cr (VI) reduction was meaningfully affected by temperature, hydrogen ion concentration, reaction time, and reactant concentrations. The reaction followed the pseudo-second-order kinetic model (R2 = 0.997) at pH of 2; at the neutral and alkaline pH (7 and 9), the reaction predominantly obeyed first order (R2 = 0.988) and pseudo-first order (R2 = 0.758), respectively. Under various hydrogen ion concentrations, the reaction retains negative free energies, enthalpy change, and a positive entropy. The findings from this study suggested the reaction to be spontaneous, exothermic, and orderly unstable. We concluded that phytocompounds present in tamarind methanol leaves extract demonstrated a strong potentials for converting Cr (VI) to Cr (III) and, thus, could be applicable in Cr (VI) contaminated wastewater treatment.

Highly efficient removal of As(III), Zn(II), Cu(II) and Cd(II) in aqueous solution using thermal desorption residue from oil sludge contaminated soil: Performance and mechanism

The thermal adsorption residue (TDR) from oil sludge co-contaminated soil was employed to remove As(III), Zn(II), Cu(II), Cd(II) in aqueous solution. The results showed that the TDR could efficiently neutralize the acid and adapt to the extensive pH. The adsorption of four heavy metals on TDR could be divided into three stages. The maximum adsorption capacity were 86.59, 249.07, 339.88, 322.86 mg·g−1 for As(III), Zn(II), Cu(II), Cd(II), respectively. The coexistence of Zn(II)/Cu(II)/Cd(II) could promote As(III) removal but As(III) led to decreasing of Zn(II)/Cu(II)/Cd(II) adsorption capacity in binary system. There was a significant competitive adsorption on TDR among the three cations which followed the selectivity sequence of Cu(II)>Zn(II)>Cd(II). The SEM-EDS, XRD, FTIR and XPS analyses demonstrated that the As(III) was removed via formation of Ca-As precipitation, and the Zn(II), Cu(II), Cd(II) were removed through precipitating as hydroxides/carbonates/silicates combining with ion exchange. Specially, the Cu(II) mainly precipitated in the form of Cu4(SO4)(OH)6⋅2H2O and Cu4(OH)6SO4 under sulfuric acid solution environment. Overall, this study indicates the potential of TDR as a cost-effective adsorbent in acid heavy metals contaminated wastewater treatment.

Sulfonamide and quinolone antibiotics contaminated wastewater treatment by constructed rapid infiltration: efficiency and microbial community structure

Four antibiotics common in wastewater, namely sulfadiazine (SD), sulfamethoxazole (SMX), ciprofloxacin (CIP), and norfloxacin (NOR), were used in the treatment of wastewater by constructed rapid infiltration (CRI), using coke as filler material. Results showed that the removal rates of chemical oxygen demand (COD), ammonia nitrogen (NH3-N) and the total phosphorus (TP) of the sulfonamide antibiotics infiltration column reached 75.01%, 40.79% and 91.22%, respectively, which were 6.61%, 12.13% and 2.68% lower than those of the quinolone antibiotics infiltration column. With increasing antibiotic concentration (2–10 mg/L), the removal of SD showed a downward trend. The average removal rates of CIP and NOR by the CRI reached 34.65% and 43.57%, respectively. Oxygen-containing functional groups of the coke played a positive role in the removal of antibiotics. The dehydrogenase (DH) activity in the sulfonamide infiltration column was 0.62 μg/(g·mL), which was 0.48 μg/(g·mL) lower than that of the quinolone infiltration column. Meanwhile, the activity of phosphatase (AKP) in the sulfonamide infiltration column was 0.06 mg/(g·h), 0.30 mg/(g·h) lower compared to that of the quinolone infiltration column. Microbial community was dominated by Actinomycetes (38.52–55.93%) at the phylum level and by Arthrobacter (34.00–49.20%) at the genus level, especially in the sulfonamide infiltration column. Based on Kyoto Encyclopedia of Genes and Genomes (KEGG) functional analysis, carbohydrate (10.79–11.52%) and amino acid metabolism (10.79–11.27%) were the main bacterial pathways. Overall, sulfonamide antibiotics more negative impacted wastewater treatment by the CRI than quinolone antibiotics.

Efficient removal of Cu(II) from an aqueous solution using a novel chitosan assisted EDTA-intercalated hydrotalcite-like compound composite: Preparation, characterization, and adsorption mechanism

Adsorption is recognized as one of the most promising methods for heavy metal removal from contaminated water. However, the adsorption efficiency often decreases because of easy aggregation and an inevitable certain loss of adsorbents during the adsorption process. Herein, a highly efficient chitosan (CS) assisted ethylenediaminetetraacetate-intercalated Mg-Al hydrotalcite-like compound (EDTA-HTlc) composite absorbent (CS-EDTA-HTlc) was synthesized by using a simple ion-exchange/chemical crosslinking process to remove Cu(II), used as a template heavy metal, from an aqueous solution. Characterization by FESEM, PXRD, FTIR, TG-DTG, BET specific surface area, and pore volume revealed that CS-EDTA-HTlc had a high specific surface area and many different functional groups (such as carboxyl, hydroxyl, and amino) with strong complexing ability. The adsorption capacity of CS-EDTA-HTlc for Cu(II) was investigated by varying experimental conditions such as adsorbent dosage, initial solution pH, adsorption time, initial Cu(II) concentration, and temperature. The adsorption equilibrium was reached within 120 min. The Cu(II) removal efficiency came 98% with the initial Cu(II) concentration of 200 mg·L-1 and the adsorbent dosage of 1.0 g·L-1. The adsorption kinetics and isotherms data of Cu(II) on CS-EDTA-HTlc were well described by the pseudo-second-order kinetic equation and the Freundlich model, respectively. The adsorption was a spontaneous exothermic process, and the possible adsorption mechanisms analyzed by the XPS and PXRD spectra involved the complexation of Cu(II) ions by carboxyl/hydroxyl/amino groups and the isomorphic substitution of Mg(II) in brucite-like layers. The results suggest that CS-EDTA-HTlc has potential applications in natural Cu(II) contaminated wastewater treatment.

Quantitative structure-activity relationship for the oxidation of organic contaminants by peracetic acid using GA-MLR method

Peracetic acid (PAA) is considered as an effective and powerful oxidant for eliminating organic contaminants in wastewater treatment. The second-order rate constant (kapp) for the reaction of PAA with organic contaminants is practically important for evaluating their removal efficiency in wastewater treatment, but only limited numbers of kapp values are available. In this study, 70 organic compounds with various structures were selected, and the kapp of PAA with each organic compound was used to develop two quantitative structure-activity relationship (QSAR) models based on three kinds of descriptors including constitutional, quantum chemical, and the PaDEL descriptors. The genetic algorithm (GA) was applied to select the molecular descriptors, then the models developed by multiple linear regression (MLR). The most important descriptors that explain the reactivity of organic compounds with PAA are the EHOMO for the model with the constitutional and quantum chemical descriptors. The maxHdsCH and minHdCH2 are two most important descriptors for the model with only PaDEL descriptors. The developed models can be used to predict kapp for a wide range of organic contaminants. The accuracy of the developed models was proved by the internal, external validation and the Y-scrambling technique. The developed QSAR models using the GA-MLR method can be used as a screening tool for predicting the elimination of organic contaminants by PAA and increasing the understanding of chemical pollutant fate.

Transcriptomics and proteomics revealed the psychrotolerant and antibiotic-resistant mechanisms of strain Pseudomonas psychrophila RNC-1 capable of assimilatory nitrate reduction and aerobic denitrification

Aerobic denitrification has been proved to be profoundly affected by temperature and antibiotics, but little is known about how aerobic denitrifiers respond to temperature and antibiotic stress. In this study, the nitrate reduction performance and the intracellular metabolism by a psychrotolerant aerobic denitrifying bacteria, named Pseudomonas psychrophila RNC-1, were systematically investigated at different temperatures (10 °C, 20 °C, 30 °C) and different sulfamethoxazole (SMX) concentrations (0 mg/L, 0.1 mg/L, 0.5 mg/L, 1.0 mg/L, and 5.0 mg/L). The results showed that strain RNC-1 performed satisfactory nitrate removal at 10 °C and 20 °C, but its growth was significantly inhibited at 30 °C. Nitrate removal by strain RNC-1 was slightly promoted in the presence of 0.5 mg/L SMX, whereas it was significantly suppressed with 5.0 mg/L SMX. Nitrogen balance analysis indicated that assimilatory nitrate reduction and dissimilatory aerobic denitrification jointly dominated in the nitrate removal process of strain RNC-1, in which the inhibition effected on assimilation process was much higher than that on the aerobic denitrification process under SMX exposure. Further transcriptomics and proteomics analysis revealed that the psychrotolerant mechanism of strain RNC-1 could be attributed to the up-regulation of RNA translation, energy metabolism, ABC transporters and the over-expression of cold shock proteins, while the down-regulation of oxidative phosphorylation pathway was the primary reason for the deteriorative cell growth at 30 °C. The promotion of nitrate reduction with 0.5 mg/L SMX was related to the up-regulation of amino acid metabolism pathways, while the down-regulation of folate cycle, glycolysis/gluconeogenesis and bacterial chemotaxis pathways were responsible for the inhibition effect at 5.0 mg/L SMX. This work provides a mechanistic understanding of the metabolic adaption of strain RNC-1 under different stress, which is of significance for its application in nitrogen contaminated wastewater treatment processes.

Dye contaminated wastewater treatment through metal–organic framework (MOF) based materials

A complete discussion of MOFs and MOF composites such as MOF-based membranes, magnetic MOFs, and metal–organic gels (MOGs) used for dye removal along with their adsorption efficiency has been done.

Synchronous Pyrolysis and Activation of Poly (Ethylene Terephthalate) for the Generation of Activated Carbon for Dye Contaminated Wastewater Treatment

Synchronous Pyrolysis and Activation of Poly (Ethylene Terephthalate) for the Generation of Activated Carbon for Dye Contaminated Wastewater Treatment

Self-supporting rGO/BiOBr composite on loofah-sponge as a floating monolithic photocatalyst for efficient microcystis aeruginosa inactivation

• An innovative design of using agricultural waste for algae inactivation is proposed. • High-efficient monolithic photocatalyst supporting on loofah sponge is fabricated. • rGO improves the adhesive of BiOBr on loofah sponge, but also facilitates charge separation. • rGO/BiOBr@LF shows high efficient algae killing activity and long term operation stability. Photocatalysis has long been considered as a promising way for water purification, however the practical application of it has been strictly hindered by the difficulty in photocatalyst recyclability. In this work we report the first use of agricultural waste of loofah sponge as catalyst host to support photocatalyst, forming a floating monolithic-like structure for algae contaminated wastewater treatment. Taking BiOBr as an example, a series of floating monolithic photocatalysts of rGO/BiOBr supporting on loofah sponge (rGO/BiOBr@LF) are fabricated, exhibiting remarkable photocatalytic activities toward microcystis aeruginosa inactivation. Among them, rGO/BiOBr@LF with rGO loading content of 1.5 wt% (rGO/BiOBr@LF-2) shows the highest photocatalytic algae degradation performance, where more than 90% of microcystis aeruginosa can be removed with the TOC removal of algae reaching 74% within 3 h photocatalysis. Furthermore, the as-prepared rGO/BiOBr@LF-2 could be simply recycled by taking the material out of the solution, while without obvious catalytic activity loss. This work offers a new insight in designing recyclable and floating monolithic photocatalyst for high-efficient practical algae wastewater treatment.

Hyaluronate macromolecules reduced-stabilized colloidal palladium nanocatalyst for azo contaminated wastewater treatment

Palladium nanoparticles (PdNPs) are of great important catalysts for a wide variety of applications. With the increasing demands of these materials, green and novel synthesis methods have become one of the leading research focuses. In obedience to the principle of an eco-friendly approach, PdNPs were developed following a one-pot green synthesis technique using sodium hyaluronate (SH) as reductant and stabilizer, which is a non-toxic, renewable, and glycosaminoglycan polymer. The synthesis protocol was spectroscopically monitored to achieve an optimum reaction condition using a one-variable-at-a-time technique where all parameters (concentration of SH, media pH, reaction time, and temperature) were tested in a set of experiments. The growth of PdNPs was evinced from intense brown color in the reaction solution and broad continuous absorption spectra in the UV–vis region. The synthesized PdNPs coated with SH-macromolecules were face-centered cubic crystal structure (d-spacing = 0.233 nm) with spherical/oval shape, uniformly polydispersed (ranged from 2.1 to 8.6 nm), smaller in size (5.3 ± 2.1 nm), and highly stabilized (zeta potential = −25.0 mV). The homogeneous catalytic performance of PdNPs exhibited almost 100% dye degradation for reactive red 195 and reactive yellow 145 by 12 and 16 min with a kinetic-constant value of 0.2128 and 0.1505 min –1 , respectively. The practical application of as-synthesized biogenic PdNPs as a nanocatalyst could be explored for the eco-friendly environmental treatment of wastewaters polluted with toxic, mutagenic, and hazardous azo dyes/pigments. • This bioreduction method is capable of synthesizing PdNPs by green and fast approach. • Hyaluronate is used as a soft matrix and reducing-stabilizing agent for PdNPs synthesis. • The high yield of the PdNPs is achieved using a one-variable-at-a-time optimization strategy. • Synthesized PdNPs are nano-sized, spherical shape, uniformly polydisperse, highly stable, and FFC crystal structure. • The synthesized PdNPs possessed excellent catalytic reduction potential against toxic azo dyes.

Highly efficient adsorbent for removal of Crystal Violet Dye from Aqueous Solution by CaAl/LDH supported on Biochar

This work presents the development of a novel highly efficient adsorbent produced from CaAl/LDH supported on biochar chemically activated with phosphoric acid [CaAl/Biochar(H3PO4)] in order to maintain a great adsorbent capacity and prevent LDH disintegration. Its adsorptive efficiency was compared to an adsorbent formed from CaAl/LDH supported on untreated biochar (CaAl/Biochar). Biochar was produced from the pyrolysis of Eucalyptus saligna sawdust. The adsorbents were applied to remove crystal violet (CV) dye from aqueous solutions in a batch adsorption process. The adsorbents were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) and scanning electron microscopy (SEM). Adsorption kinetics, isotherms and thermodynamics were evaluated. The characterization results suggested that the CaAl/LDH was successfully synthesized and supported on biochar. The results indicate that pH 8 was more suitable for CV dye adsorption, with an adsorptive capacity over 101 mg g−1 for CaAl/Biochar(H3PO4). Furthermore, adsorption experimental data fitted well with the pseudo-second order kinetics model and the Freundlich isotherm model. It was obtained a maximum adsorption capacity of 496.55 mg·g−1 at 50 °C. For CaAl/Biochar(H3PO4), the thermodynamic results revealed a favorable, spontaneous and endothermic process. In addition, the results showed that the pre-treatment of the biochar with phosphoric acid maintained 71% of the initial adsorptive capacity even after four cycles of reuse. Therefore, CaAl/Biochar(H3PO4) is a sustainable adsorbent with high performance for CV contaminated wastewater treatment and groundwater remediation.