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1.
Chemosphere ; 262: 128031, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33182077

RESUMO

In this research, raw jujube seeds (RJS) treated with sulphuric acid followed by ultrasonic treatment such as ultrasonic assisted jujube seeds (UAJS) based biochar have been experimented as a viable material for treating Zn(II) and Pb(II) contaminated water. The adsorption ability of UAJS was compared with RJS through Langmuir adsorption capacity. The produced adsorbents were analysed by using BET surface area and thermogravimetric analyses. The removal kinetics, isotherms and thermodynamic behaviours of metal ions adsorption by UAJS were studied. Adsorption equilibrium data were analysed using various equilibrium models and Freundlich isotherm was appropriate towards explain the adsorption characteristics. UAJS Langmuir capacity of 221.1 mg/g and 119.8 mg/g were obtained for Zn(II) ions and Pb(II) ions, respectively. The results observed that UAJS holds higher capacity as compared with RJS. The pseudo-first order model was relevant to address adsorption behaviour. The mechanism on the separation of metal ions by UAJS was tested using diffusion and Boyd models. The mechanism outcomes observed that the internal and external diffusion controlled the separation process. The thermodynamic results explain the separation process was viable, exothermic and natural. The electroplating industrial wastewater was also treated with UAJS biochar to remove the metal ions such as copper, nickel, chromium and zinc ions from wastewater. Desorption process showed that 0.1 N HCl provide the good results as compared with other desorbing agents. The adsorbent property is not lost till the maximum of 5 adsorption/desorption cycles. The produced UAJS can be a better adsorbent for treating the heavy metal polluted wastewater.


Assuntos
Carvão Vegetal/química , Galvanoplastia , Metais Pesados/análise , Águas Residuárias/química , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Adsorção , Difusão , Íons , Cinética , Sementes/química , Termodinâmica , Ziziphus/química
2.
J Environ Sci (China) ; 99: 130-142, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33183690

RESUMO

Generation of alum sludge (AS) at drinking water treatment plants represents an environmental liability and adds to the cost of water purification. Consequently, this study explored the feasibility of using low and high carbon containing alum sludge from two water treatment plants to synthesize zeolite LTA. The hypothesis was that zeolite LTA synthesis was dependant upon alum sludge source and that a range of strategies may be required to optimize zeolite crystallinity. Zeolite characteristics such as morphology, phase composition, crystallinity, and particle size distribution were recorded. "One pot" hydrothermal synthesis of precursor gel with molar composition 4.2Na2O:Al2O3:1.2SiO2:168H2O at 80°C for 3 hr resulted in 25 and 46 wt.% zeolite LTA from high and low carbonaceous sludge, respectively. Prior to hydrothermal reaction stage it was discovered that ageing of the gel, addition of zeolite LTA seeds, ultrasonic treatment and calcination all promoted zeolite LTA formation. Calcination of the alum sludge at 700°C for 2 hr before hydrothermal synthesis resulted in particle size reduction and the highest amount of crystalline zeolite LTA: 79 wt.% from low carbon sludge and 65 wt.% from high carbon sludge. Notably, the zeolite crystallinity reported in this study was the higher than previous studies on this topic. The outlined approach may allow value adding of alum waste and produce a commodity which could be used locally by the water treatment plant as a water softener.


Assuntos
Purificação da Água , Zeolitas , Compostos de Alúmen , Esgotos
3.
J Environ Sci (China) ; 99: 151-159, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33183692

RESUMO

Disinfection byproducts (DBPs) represent a ubiquitous source of chemical exposure in disinfected water. While over 700 DBPs have been identified, the drivers of toxicity remain poorly understood. Additionally, ever evolving water treatment practices have led to a continually growing list of DBPs. Advancement of analytical technologies have enabled the identification of new classes of DBPs and the quantification of these chemically diverse sets of DBPs. Here we summarize advances in new workflows for DBP analysis, including sample preparation, chromatographic separation with mass spectrometry (MS) detection, and data processing. To aid in the selection of techniques for future studies, we discuss necessary considerations for each step in the strategy. This review focuses on how each step of a workflow can be optimized to capture diverse classes of DBPs within a single method. Additionally, we highlight new MS-based approaches that can be powerful for identifying novel DBPs of toxicological relevance. We discuss current challenges and provide perspectives on future research directions with respect to studying new DBPs of toxicological relevance. As analytical technologies continue to advance, new strategies will be increasingly used to analyze complex DBPs produced in different treatment processes with the aim to identify potential drivers of toxicity.


Assuntos
Desinfetantes , Poluentes Químicos da Água , Purificação da Água , Desinfetantes/análise , Desinfecção , Halogenação , Água , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/toxicidade
4.
Chemosphere ; 262: 127853, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-32777616

RESUMO

Green rusts (GRs) are redox active towards contaminants but they are not stable for long distance transport during the soil and groundwater remediation. In this study, green rust chloride (GR) was stabilized by selected regents, including silicate (Si), phosphate (P), fulvic acid (FA), carboxymethyl cellulose (CMC) and bone char (BC), then these stabilized GR, collectively named GR-X, would be further applied for Cr(VI) removal from aqueous solution. The stabilization experiment demonstrated that the release of Fe(II) from GR was effectively suppressed by above reagents, enabling at least 50% lower Fe(II) leaching from the stabilized GR-X than that from the pristine GR. The intact hexagonal GR plates and crystallinity were also confirmed by the SEM images and XRD patterns after storage for 7 days, indicating the stable structure of GR-X was remained. In the Cr(VI) removal tests, Cr(VI) was eliminated by GR-X in seconds with a Fe(II) utilization efficiency over 90%. The Cr species examination demonstrated that the GR-X was able to transfer Cr(VI) into stable Cr(III)-Fe(III) precipitates (Fe-Mn oxides fraction). After Cr(VI) removal tests, all reactors were exposed to the air for 1 week to monitor pH fluctuation and evaluated the risk of acidification. The results indicate that, except for GR-Si system, the other post-remediation systems are stable and the pH buffering ability of GR-X could avoid acidification and lower the Cr leaching risk.


Assuntos
Cromo/química , Poluentes Químicos da Água/química , Purificação da Água/métodos , Carboximetilcelulose Sódica , Cromo/análise , Água Subterrânea , Ferro/química , Cinética , Oxirredução , Óxidos , Solo/química , Água/química , Poluentes Químicos da Água/análise
5.
Chemosphere ; 262: 127820, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-32781332

RESUMO

In this study, the behavior of mono-component (metronidazole/phosphate/nitrate, MET/PO43-/NO3-) and multi-component (MET+PO43-+NO3-) adsorption in fixed-bed adsorption column was investigated using Prosopis juliflora activated carbon (PJAC). The influence of column operating parameters such as bed depth (H: 5-15 cm), influent flow rate (Q: 0.5-2 L/h) and adsorbate concentration (Co: 25-100 mg/L) on breakthrough curves were evaluated. The experimental data was correlated with breakthrough models viz. Thomas, Adams-Bohart, Yoon-Nelson and bed depth service time (BDST) models. The results showed that the Thomas model fitted the experimental data better than other models in predicting the breakthrough characteristics for the removal of MET, PO43- and NO3- by PJAC. The maximum adsorption capacity found by Thomas model was 9.70, 8.21 and 5.57 mg/g for MET, PO43- and NO3-, respectively. In multi-component systems, antagonistic behavior in sorption of MET, PO43- and NO3- was observed and as a result, adsorption capacity was 1.2-1.5 folds lesser than that observed in mono-component system. In conclusion, results of the present study indicate that the PJAC can be successfully employed for the removal of MET, PO43- and NO3- using fixed-bed adsorption column; however, the column design for multi-component mixture should be based on rapid breakthrough sorbate.


Assuntos
Carvão Vegetal/química , Prosopis , Poluentes Químicos da Água/química , Purificação da Água/métodos , Adsorção , Antibacterianos , Nutrientes , Poluentes Químicos da Água/análise
6.
Chemosphere ; 262: 127836, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-32805657

RESUMO

Polyacrylonitrile fiber was successfully modified with triazine-based dendrimer via grafting method as a promising adsorbent for removal of mercury species from aqueous media. The prepared adsorbent was characterized by elemental analysis, scanning electron microscope, Fourier transform infrared spectroscopy, porous structure analysis and X-ray photoelectron spectroscopy, providing the evidence of successful fabrication. The adsorption conditions were found via varying pH, dosage, coexisting substances, contact time, temperature and concentration. Adsorption performance, described better by the pseudo-second-order kinetics with intraparticle diffusion as rate controlling step and Langmuir isotherm model, indicated a chemisorption process with the maximum Langmuir adsorption amount of 227.64 mg g-1 for mercury ions. Thermodynamically, adsorption of mercury ions was spontaneous and endothermic. Desorption and regeneration experiments demonstrated that it could be reused in five successive adsorption cycles without significant loss of its original performance. Experimental data and density functional theory calculation disclosed the coordination geometries and chelating mechanism between the adsorbent and mercury ions. The proposed study would provide a new prospect for the purification of mercury in aqueous system by functionalizing commercial polyacrylonitrile fiber with dendrimers.


Assuntos
Resinas Acrílicas/química , Dendrímeros/química , Poluentes Químicos da Água/química , Purificação da Água/métodos , Adsorção , Difusão , Concentração de Íons de Hidrogênio , Íons/análise , Cinética , Mercúrio/análise , Temperatura , Termodinâmica , Águas Residuárias/química , Água/química , Poluentes Químicos da Água/análise
7.
Sci Total Environ ; 750: 141691, 2021 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-32853938

RESUMO

This work focused on the impacts of FeCl3 impregnation ratio on the properties of FeCl3-activated bermudagrass (BG)-derived biochars (IA-BCs), adsorption of sulfamethoxazole (SMX) onto IA-BCs and regeneration of SMX-spent IA-BC. Compared with the control BC (85.82 m2/g), IA-BCs made via pyrolysis with FeCl3 to BG mass ratio between 1 and 3 (1-3 g FeCl3/g BG) resulted in significantly enhancing surface area (1014-1035 m2/g), hydrophobicity, Fe content in IA-BCs (3.87-7.27%), and graphitized carbon. The properties of IA-BCs supported magnetic separation and higher adsorption (32-265 mg SMX/g BC) than the control BC (6-14 mg SMX/g BC) at various pH. Adsorption experiments indicated various adsorption mechanisms between SMX and IA-BCs via π-π EDA, hydrophobic interactions, and hydrogen bond with intraparticle diffusion limitation. The adsorption was also found to be spontaneous and exothermic. The IA-BC made at FeCl3 to BG mass ratio of 2 (IA-BC2.0) showed the maximum adsorption capacity for SMX (253 mg SMX/g BC) calculated from Langmuir isotherm model. Additionally, both NaOH desorption and thermal oxidation showed effective regeneration of SMX-saturated IA-BC2.0 over multiple cycles. After three cycles of adsorption-regeneration, 64% and 62% of regeneration efficiencies were still achieved under thermal treatment at 300 °C and desorption with 0.1 M NaOH solution, respectively, indicating a cost-efficient adsorbent for the elimination of SMX in water.


Assuntos
Poluentes Químicos da Água , Purificação da Água , Adsorção , Carvão Vegetal , Cynodon , Ferro , Sulfametoxazol , Poluentes Químicos da Água/análise
8.
Sci Total Environ ; 751: 141310, 2021 Jan 10.
Artigo em Inglês | MEDLINE | ID: mdl-32861185

RESUMO

Health care facilities can represent point sources for pharmaceutical residues in public sewer systems. Compared to general hospitals, more specialized health care facilities might also have a different pattern of medication. Therefore, the on-site treatment of wastewater from such facilities could be an effective strategy to reduce emissions into water bodies and was the aim of this study. Wastewater from three health care facilities (nursing home, clinic with orthopaedic focus, and psychiatric clinic) was treated in lab-scale and semi-industrial trials. Biological treatment was performed via an ultrafiltration membrane bioreactor (UF-MBR), after which adsorption onto granular activated carbon (using rapid-small-scale column tests GAC-RSSCT), ozonation and a UV/H2O2 advanced oxidation process (AOP) were tested and compared. The removal of 17 pharmaceutical compounds and drug metabolites from 9 drug classes (e.g. analgesics, antibiotics, anticonvulsants) was evaluated. Most of the measured OMP were detected with concentrations between 1,000 and 30,000 ng L-1 in the influent of the MBR. The UF-MBR provided an effective mechanical-biological cleaning of the wastewater, with micropollutant removal efficiencies between 0 and > 95%, making further treatment necessary to remove the micropollutants. Each combination of the UF-MBR with one of the three further treatments achieved removal efficiencies above 80% for most of the investigated substances, reducing many to below the quantification limit of 10 ng L-1. The results show the general suitability of combining the UF-MBR with either GAC-adsorption, ozonation or AOP for eliminating pharmaceutical residues. However, the AOP process has a significantly higher energy demand than the other two processes. Moreover, specific settings and dosages depend on the respective wastewater matrix.


Assuntos
Preparações Farmacêuticas , Poluentes Químicos da Água , Purificação da Água , Reatores Biológicos , Peróxido de Hidrogênio , Eliminação de Resíduos Líquidos , Águas Residuárias , Poluentes Químicos da Água/análise
9.
Sci Total Environ ; 751: 141572, 2021 Jan 10.
Artigo em Inglês | MEDLINE | ID: mdl-32871311

RESUMO

The robustness of anaerobic dynamic membrane bioreactor (AnDMBR) for synthetic textile wastewater treatment was investigated. Textile wastewater may contain high concentrations of NaCl and sulfate, hence their impact on the AnDMBR performance was investigated in detail. A dynamic membrane was formed on a 20-µm pore sized nylon support layer at a constant flux of around 8 LMH. In the absence of sulfate addition, total and filtered (soluble) COD averaged 96 ± 49 mg/L (91% removal) and 75 ± 35 mg/L (93% removal), respectively. Sulfate addition increased total COD in the permeate to 222 ± 68 mg/L (79% removal). Average SS concentration was lower than 30 mg/L in the permeate although its concentration in the bioreactor reached 10 g/L. Throughout the AnDMBR operation dye removal averaged >97%. Sludge filterability, which was assessed by specific resistance to filtration, supernatant filtration, capillary suction time and viscosity, decreased after sulfate addition. Organic and inorganic matters in the dynamic layer were characterized by SEM-EDS and FTIR analyses.


Assuntos
Águas Residuárias , Purificação da Água , Anaerobiose , Reatores Biológicos , Membranas Artificiais , Indústria Têxtil , Eliminação de Resíduos Líquidos
10.
Sci Total Environ ; 751: 141777, 2021 Jan 10.
Artigo em Inglês | MEDLINE | ID: mdl-32871317

RESUMO

Cells have inherent anti-fouling properties. The mechanisms underpinning these natural properties inform the design of an anti-biosorption coating for a polyethersulfone microfiltration membrane, which includes polydopamine and chitosan layers. This tri-layered membrane is created using quick and easy synthesis method. Its ability to resist bio-adsorption and membrane extracellular polymeric substances (EPS) formation is investigated using the bacterium E. coli (ATCC 11775, 1.5 × 107 CFU/mL). In addition, the proliferative bio-adsorption process is explored on the microfiltration membrane surface, using natural water under static and shaken conditions, while monitoring the bio-adsorption kinetics and EPS dynamic changes. The characterization results show that the modification by polydopamine and chitosan change the membrane surface morphology and increase its hydrophilicity. After 10 min dipping in 5 g/L chitosan solution, the pure water flux of the modified membrane is 5469 ± 30 L/(m2·h) (0.2 bar) and the contact angle decreases to 36.7 ± 1.0°, compared with 9889 ± 23 L/(m2·h) (0.2 bar) and 60.3 ± 1.5° for the unmodified polyethersulfone membrane, respectively. In proliferative bio-adsorption tests, the modified membrane is shown to decrease bio-adsorption by 0.4-2.3 orders of magnitude. However, no antimicrobial function is observed, probably due to the alkaline environment and insufficient functional amino groups. A series of linear and non-linear kinetic models is applied to fit the proliferative bio-adsorption process. The pseudo-second-order model is found to describe the proliferative bio-adsorption process best. Neither total organic carbon (TOC) nor protein is detected on the modified membrane surface. In contrast, on the unmodified PES membrane the ratios of protein/TOC (%), TOC/abundance ((µg/cm2)/CFU (log)) and protein/abundance ((µg/cm2)/CFU(log)) are 10%-16%, 0.17-0.28 and 0.02-0.04, respectively. No significant difference (p > 0.05) is found between static and shaken conditions. All these results point to improved anti-biosorption properties for water treatment applications, encouraging further studies on this membrane.


Assuntos
Escherichia coli , Purificação da Água , Adsorção , Interações Hidrofóbicas e Hidrofílicas , Membranas Artificiais
11.
Sci Total Environ ; 751: 141623, 2021 Jan 10.
Artigo em Inglês | MEDLINE | ID: mdl-32877793

RESUMO

There is a growing interest in the use of adsorbent nanoparticles to mitigate the toxic effects of pollutants in natural matrices. However, due to their small size, nanoparticles have the potential to transport and disseminate contaminants adsorbed on their surfaces into environmental compartments with greater risk to human, animal, or plant health. This potential consequence of nanoparticle application remains largely unstudied. Here, we studied the application of three adsorbents, including zeolite (Z, micrometric size), nanomagnetite (Mt), and a nanomagnetite-zeolite composite (MtZ) intended to mediate arsenic toxicity in hydroponic tomato cultures. Adsorption studies showed an arsenate adsorption sequence of MtZ (6.2 mg g-1) ≥ Mt (4.7 mg g-1) â‰« Z (0.3 mg g-1). Tomatoes grown under the Mt condition demonstrated the lowest growth rate (4.2 cm), corresponding to a 45% decrease compared to the control (7.6 cm), as well as the highest oxidative stress level (0.024 µmol g-1) as indicated by malondialdehyde (MDA) concentration, almost twice the control (0.014 µg g-1). Tomatoes grown under MtZ conditions showed a 22% decreased growth (5.9 cm) but MDA levels (0.012 µmol g-1) were comparable to the control. Together, these results suggest that Mt at the nanometric size could obstruct channels in the plant and prevent absorption of water and nutrients. Anchoring nanomaterials in larger composites of micrometer size presents a promising alternative that would retain their super-adsorbent properties while avoiding toxicity due to nanometric size.


Assuntos
Arsênico , Lycopersicon esculentum , Poluentes Químicos da Água , Purificação da Água , Zeolitas , Adsorção , Arsênico/análise , Humanos , Concentração de Íons de Hidrogênio , Hidroponia , Cinética , Poluentes Químicos da Água/análise
12.
Sci Total Environ ; 750: 141498, 2021 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-32882491

RESUMO

This work examined the adsorption capacity of sugarcane bagasse (SB) for the removal of ciprofloxacin (CPX) from water using batch experiments and a fixed bed column and compared its adsorption performance with a powdered activated commercial carbon (PAC). Both adsorbents achieved a similar percentage removal of about 78% with doses of 3 g L-1 of SB and 0.3 g L-1 of PAC (20 mg L-1 initial CPX concentration at 30 °C). The maximum removal was obtained at a pH between 6 and 8. SB adsorption isotherms were fitted to the Langmuir, BET and Freundlich models showing a maximum adsorption capacity of 13.6 mg g-1. The kinetic data for both SB and PAC fitted the pseudo second-order model (R2 = 0.99). The adsorption process was faster on the SB (65% of elimination in the first 5 min) than on the PAC. The study of the adsorbent properties shows that SB is a macroporous solid with a specific surface area 250 times smaller than PAC. The thermodynamic results show that SB adsorption was physical and exothermic. The main suggested interactions between CPX and SB are electrostatic attraction, hydrogen bonding and dipole-dipole interactions. The experiments carried out in a fixed bed show that the adsorption capacity at breakthrough increases with the bed height. The adsorption capacity at saturation time was 9.47 mg g-1 at a flow rate of 3 mL min-1, a bed height of 14 cm, and a diameter of 1.5 cm. The experimental data were fitted to the Bohart-Adams model (R2 = 0.98). These results highlight the capacity of sugarcane bagasse to adsorb ciprofloxacin from water, illustrating its potential as a low-cost adsorbent.


Assuntos
Saccharum , Poluentes Químicos da Água , Purificação da Água , Adsorção , Celulose , Carvão Vegetal , Ciprofloxacino , Equador , Concentração de Íons de Hidrogênio , Cinética , Pós
13.
Sci Total Environ ; 751: 141409, 2021 Jan 10.
Artigo em Inglês | MEDLINE | ID: mdl-32882545

RESUMO

To address the adverse effects of harmful algal blooms, there are increased demands over the implementation of ozone coupled with biologically active carbon (BAC) filters in the drinking water treatment plants. Although the microbial biofilms are vital elements to support the proper performance of BAC filters, except for taxonomic affiliations, little is known about the assembly mechanisms of microbial communities in the full-scale BAC filters. This study aimed to examine how the assembly processes and their associated factors (e.g., influent characteristics, biological interactions) drive the temporal dynamics of bacterial communities in full-scale BAC filters, which underwent ozone implementation (five consecutive seasons from 2017 to 2018). The results revealed that along with the increase of bacterial taxonomic richness and evenness, stochastic processes became more crucial to determine the bacterial community assembly in the summer and autumn after ozone implementation (relative contribution: 61.23% and 83.75%, respectively). Moreover, their corresponding networks possessed simple network structures with lower modularity than other seasons, which implied lesser biological interactions among bacterial populations. The correlation between taxonomic and predicted functional diversities using functional redundancy index indicated that relatively high levels of bacterial functional redundancy (>0.83) were generally present in BAC filters. However, compared to other seasons, significantly higher degrees of functional redundancy existed in the summer and autumn after ozone implementation (0.85 ± 0.01 and 0.86 ± 0.01, respectively). Overall, this work improves our understanding of the microbial ecology of full-scale BAC filters by providing a conceptual framework that characterizes bacterial biofilm assembly processes relevant to performance optimization of full-scale BAC filters.


Assuntos
Ozônio , Purificação da Água , Bactérias , Biofilmes , Carvão Vegetal
14.
Sci Total Environ ; 751: 141660, 2021 Jan 10.
Artigo em Inglês | MEDLINE | ID: mdl-32889458

RESUMO

A new NiAlFe layered double hydroxide/polydopamine/polyvinylidene fluoride (NiAlFe LDH/PDA/PVDF) membrane was fabricated by in-situ growth of LDH on the PDA modified PVDF membrane. The as-prepared membrane possesses a nano/microscale rough structural surface and displays the superior wettability of superhydrophilicity in air and underwater superoleophobicity. Combining the favourable features of superwettability and hierarchical rough structure, the NiAlFe LDH/PDA/PVDF membrane could effectively separate a series of oil-in-water emulsions with high efficiency (>99%) and high permeation flux (925-1913 L m-2 h-1 bar-1). Besides, owing to the light harvest ability of NiAlFe LDH, the relevant membrane also can be applied as a photocatalysis paper for the light-driven treatment of antibiotic residue in aqueous solution. In which, NiAlFe LDH/PDA/PVDF membrane can effectively degrade typical antibiotic tetracycline within 20 min under UV light irradiation, exhibiting excellent photocatalytic activity. In addition, cyclic experiments demonstrate that NiAlFe LDH/PDA/PVDF membrane has excellent stability and reusability both in oil-in-water emulsion separation and photocatalytic reaction. In general, the findings of this research demonstrate that photo-response LDH modified membranes have potential multiple applications in wastewater treatment.


Assuntos
Purificação da Água , Antibacterianos , Interações Hidrofóbicas e Hidrofílicas , Membranas Artificiais , Águas Residuárias
15.
Chemosphere ; 262: 128102, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33182125

RESUMO

Novel pectin derived from sweet potato residue was modified by high hydrostatic pressure (HHP)-assisted pectinase and then used for Pb2+ removal from aqueous solutions. The removal characteristics and mechanisms were also investigated. Results showed that modified sweet potato pectin exhibited greater adsorption performances for Pb2+ than that of natural ones, and showed excellent eco-friendly properties and good potential for adsorption of some other heavy metals (such as Cu2+). The adsorption curves were much more conformed to Langmuir model, and the highest capacity for Pb2+ adsorption was 263.15 mg/g with 1.00% pectin at pH 7. Chemical adsorption process of pectin for Pb2+ absorption involved O-containing functional groups (O-H, COO-), cation exchange, and along with electrostatic interactions. Overall, the results in this study indicated that sweet potato pectin modified with HHP-assisted pectinase had the potential to become an environmentally friendly coagulant-flocculant agent for the heavy metal adsorption, especially for Pb2+.


Assuntos
Pressão Hidrostática , Ipomoea batatas/química , Chumbo/análise , Pectinas/química , Poligalacturonase/química , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Adsorção , Concentração de Íons de Hidrogênio , Cinética , Pectinas/isolamento & purificação , Águas Residuárias/química
16.
Chemosphere ; 262: 128215, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33182126

RESUMO

The effluent from conventional treatment process (including anaerobic digestion and anoxic-oxic treatment) for pig farm wastewater was difficult to treat due to its low ratio of biochemical oxygen demand to chemical oxygen demand (BOD5/CODCr) (<0.1). In the present study, electro-Fenton (EF) was used to improve the biodegradability of the mentioned effluent and the properties of self-prepared CeO2-doped multi-wall carbon nanotubes (MWCNTs) electrodes were also studied. An excellent H2O2 production (165 mg L-1) was recorded, after an 80-min electrolysis, when the mass ratio of MWCNTs, CeO2 and pore-forming agent (NH4HCO3) was 6:1:1. Results of scanning electron microscopy (SEM), transmission electron microscope (TEM) and x-ray photoelectron spectroscopy (XPS) showed that addition of NH4HCO3 and the doping of CeO2 could increase the superficial area of the electrode as well as the oxygen reduction reaction (ORR) electro-catalytic performance. The BOD5/CODCr of the wastewater from the first stage AO process increased from 0.08 to 0.45 and CODCr reduced 71.5% after an 80-min electrolysis, with 0.3 mM Fe2+ solution. The non-biodegradable chemical pollutants from the first stage AO process were degraded by EF. The non-biodegradable pollutants identified by LC-MS/MS in the effluent from AO process including aminopyrine, oxadixyl and 3-methyl-2-quinoxalinecarboxylic acid could be degraded by EF process, with the removal rates of 81.86%, 34.39% and 7.13% in 80 min, and oxytetracycline with the removal rate of 100% in 20 min. Therefore, electro-Fenton with the new CeO2-doped MWCNTs cathode electrode will be a promising supplement for advanced treatment of pig farm wastewater.


Assuntos
Cério/química , Eletrólise/métodos , Nanotubos de Carbono/química , Águas Residuárias/química , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Animais , Biodegradação Ambiental , Análise da Demanda Biológica de Oxigênio , Catálise , Eletrodos , Fazendas , Peróxido de Hidrogênio/análise , Oxirredução , Suínos
17.
Chemosphere ; 262: 128072, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33182132

RESUMO

A new synthesis method was developed to prepare an aluminum-based metal organic framework (MIL-96) with a larger particle size and different crystal habits. A low cost and water-soluble polymer, hydrolyzed polyacrylamide (HPAM), was added in varying quantities into the synthesis reaction to achieve >200% particle size enlargement with controlled crystal morphology. The modified adsorbent, MIL-96-RHPAM2, was systematically characterized by SEM, XRD, FTIR, BET and TGA-MS. Using activated carbon (AC) as a reference adsorbent, the effectiveness of MIL-96-RHPAM2 for perfluorooctanoic acid (PFOA) removal from water was examined. The study confirms stable morphology of hydrated MIL-96-RHPAM2 particles as well as a superior PFOA adsorption capacity (340 mg/g) despite its lower surface area, relative to standard MIL-96. MIL-96-RHPAM2 suffers from slow adsorption kinetics as the modification significantly blocks pore access. The strong adsorption of PFOA by MIL-96-RHPAM2 was associated with the formation of electrostatic bonds between the anionic carboxylate of PFOA and the amine functionality present in the HPAM backbone. Thus, the strongly held PFOA molecules in the pores of MIL-96-RHPAM2 were not easily desorbed even after eluted with a high ionic strength solvent (500 mM NaCl). Nevertheless, this simple HPAM addition strategy can still chart promising pathways to impart judicious control over adsorbent particle size and crystal shapes while the introduction of amine functionality onto the surface chemistry is simultaneously useful for enhanced PFOA removal from contaminated aqueous systems.


Assuntos
Alumínio/química , Caprilatos/análise , Fluorcarbonetos/análise , Dietilamida do Ácido Lisérgico/análogos & derivados , Estruturas Metalorgânicas/química , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Resinas Acrílicas/química , Adsorção , Carvão Vegetal/química , Dietilamida do Ácido Lisérgico/química , Tamanho da Partícula , Solubilidade , Propriedades de Superfície
18.
Chemosphere ; 262: 128032, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33182153

RESUMO

Effective and practical materials are important for the pollution control in the environment. A novel magnetic molecularly imprinted polymer (CoFe2O4@TiO2-MMIP) was prepared based on the surface molecular imprinting technology combined with photocatalytic degradation and magnetic separation. The adsorption rate constant and maximum adsorption capacity of CoFe2O4@TiO2-MMIP are 0.21 g mg-1 min-1 and 14.26 mg g-1, respectively. The effects of experimental factors on the adsorption properties of the magnetic molecularly imprinted polymer were investigated. CoFe2O4@TiO2-MMIP had selective adsorption ability towards fluoroquinolones. The adsorption efficiency was closely related to the molecular structure, molecular weight, polarity and functional groups of the target contaminant and the removal efficiency of norfloxacin was affected by another substance obviously in binary adsorption system. The adsorption-photocatalytic recycling experiment verified that CoFe2O4@TiO2-MMIP could simultaneously complete the degradation of pollutants and in-situ regeneration, indicating good reusability. This material with selective adsorption and photocatalytic regeneration would have substantial attraction for application in the removal of fluoroquinolones.


Assuntos
Campos Magnéticos , Impressão Molecular , Norfloxacino/análise , Polímeros/química , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Adsorção , Catálise , Modelos Teóricos , Fotoquímica , Propriedades de Superfície , Raios Ultravioleta
19.
Chemosphere ; 262: 128073, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33182155

RESUMO

Due to the multi-catalysis of the WO3 and excellent properties of the graphene (GO), a series of rGO-WO3 nanocomposites were prepared through the hydrothermal synthesis procedure by changing the material ratio, the reaction temperature and the reaction time in this paper, and then added it into a dielectric barrier discharge plasma (DBDP) system for investigating the bisphenol A (BPA)'s degradation and corresponding catalytic mechanism of the rGO-WO3 in the DBDP system. The obtained results show that there was an optimum dosage of the rGO-WO3 (40 mg/L) as well as the preparation conditions (5:1000 mass ratio of the GO and the WO3, 18 h reaction time and 120 °C reaction temperature) for achieving the highest catalytic effect, and the highest degradation rate constant of the BPA was 0.03129 min-1. The determined higher TOC removal, higher COD removal as well as UV-Vis analysis also demonstrated the catalysis of the rGO-WO3. The measurement of the change of the O3 and the H2O2 concentrations in the reaction system with or without the rGO-WO3 and with or without the BPA proved the catalysis of the rGO-WO3 on the ·OH formation, while the combination of the GO had the positive effect for enhancing the catalytic effect. A figure on the catalysis and degradation procedure of the BPA in the DBDP/rGO-WO3 system was provided in the paper.


Assuntos
Compostos Benzidrílicos/análise , Grafite/química , Nanocompostos/química , Óxidos/química , Fenóis/análise , Tungstênio/química , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Catálise , Peróxido de Hidrogênio/química , Modelos Teóricos , Oxirredução , Ozônio/química
20.
Chemosphere ; 262: 128379, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33182079

RESUMO

The co-existence of heavy metals and organics in industrial effluents is a prevalent problem. These pollutants usually have dissimilar compositions and properties, making their complete removal very tedious even with the use of conventional methods. In some cases, organics and heavy metals usually exist in a mixed matrix in industrial wastes. This poses harmful health risks to humans, aquatic lives and the entire ecosystem, because majority of these mixed pollutants amass in water in concentrations which are more than the permissible discharge limits in the environment. Therefore, it is necessary to remove these pollutants in order to prevent them from contaminating both the surface and ground water. Although, the removal of organic compounds and heavy metals (such as Hg, Pb, Cd, As and Cr) could be easily achieved individually, however, these pollutants exist together in many industrial effluents and even in surface waters. Hence the complete removal of these pollutants concurrently in a polluted system is the focus of this study. Several technologies have been used for the simultaneous removal of organics and heavy metal pollutants from water, which includes adsorption, ion exchange, photocatalysis, and coagulation. The success of these techniques depends on the water matrices and the choice of water treatment media such as adsorbents, resins, photocatalysts, and coagulants. The advantages and limitations of these technologies together with their respective mathematical modelling is critically examined in this review. Finally, the effect of joint existence of organic pollutants and heavy metals on the removal efficiency were examined in addition to the mathematical models that discusses the mechanisms of their combine elimination.


Assuntos
Resíduos Industriais , Metais Pesados/análise , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Adsorção , Ecossistema , Indústrias , Águas Residuárias
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