Metal Coagulants Research Articles

Moringa oleifera seed defatted press cake based biocoagulant for the treatment of coal beneficiation plant effluent

This study proposes a unique way of preparation of biocoagulant from Moringa oleifera defatted seed press cake. The press cake used in this study is a waste material produced as a by-product during cold press oil making from Moring oleifera seeds. The prepared Moringa oleifera seed defatted press cake based biocoagulant was found more effective than presently used metallic and polymer-based coagulants and flocculants for removal of fine particles of colloidal size from the effluent generated in the process of coal beneficiation. The detailed characterization of Moringa oleifera defatted seed press cake and the prepared biocoagulant for Particle size, Field Emission Scanning Electron Microscopy, Energy Dispersive X-Ray analysis, Zeta Potential, Fourier-transform Infrared Spectroscopy, etc. was done. The biocoagulant has been found effective in 97.4% total suspended solids removal and 97.48% turbidity removal from coal beneficiation plant effluent. The biocoagulant has been found to work satisfactorily under high fluxes of turbidity and total suspended solids with high removal of fine particles. The age of biocoagulant had negligible effect on fine particle removal efficiency (97.4% for fresh to 95% for 3-week-old biocoagulant). Field Emission Scanning Electron Microscopy analysis reveals considerable increase in flocs size from 198 nm to a 20 μ size well-developed flocs. The biocoagulant has proved as an efficient substitute of the metallic and polymer-based coagulants for the efficient treatment of coal beneficiation plant effluent.

Behaviour of ozone in the hybrid ozonation-coagulation (HOC) process for ibuprofen removal: Reaction selectivity and effects on coagulant hydrolysis

Simultaneous ozonation and coagulation can be realized in one unit in the developed hybrid ozonation-coagulation (HOC) process. To reveal the reaction sequence within the HOC process, the ibuprofen (IBP) removal efficiency of the ozonation only, HOC and HOC-PO43− (inhibition of the reactions between ozone and metal coagulant) processes at pH 5 and different ozone dosages were investigated. The removal efficiency is almost the same for the three processes at a low ozone dosage (4.8 mg/L), and higher removal performance can be achieved by the HOC process with increasing ozone dosage. It can be implied that ozone preferentially reacts with OH− to generate OH which react with IBP in the HOC process, and subsequently reacts with the surface hydroxyl groups of hydrolysed Al species to enhance OH generation. Moreover, based on the kinetics, X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR) analyses, the synergistic reactions between ozone and the metal coagulants (SOC) started to take effect from ozone dosage of 9.6 mg/L, which further verified that ozone will be involved in the IBP ozonation prior to the SOC reactions. The subsequent SOC reactions also resulted in the increased generation of polymeric Al species and more abundant intermediates in the HOC process.

Characteristic properties and recyclability of the aluminium fraction of MSWI bottom ash.

The increasing use of aluminimum in packaging applications results in many different aluminium-based products ending up in consumer mixed-waste bins. This waste is typically incinerated, generating an aluminium-containing bottom ash. The current work investigates the recyclability of the aluminium fraction in the bottom ash from waste incineration plants in the USA, UK and Denmark. Incinerated Al-samples from different size fractions (2-6mm, 6-12mm and 12-30mm) were characterized in terms of inherent oxide thickness, re-melting yield/coagulation and composition. The measured average oxide thickness on Al particles was 68µm(SD=100), with the metal yield and coagulation efficiency measured to between 76 and 92% and 87-99% respectively. Larger particle size fractions resulted in a higher metal yield due to their higher mass to surface ratio. A simplified model correlating metal yield and particle size was proposed. The aluminium content of the melted material was determined to between 95.6 and 98.5% with main impurities being Fe, Si, Mn, Zn, Mg and Cu, corresponding to major aluminium alloying elements and waste charge components.

Recent advancement in starch modification and its application as water treatment agent

The exploration of effective natural coagulant materials has never been ceased despite the superiority of synthetic and metallic coagulants. Numerous research outputs have been reported by many extensive studies using a wide variety of natural precursors for water clarification. The current paper outlines the scattered findings on factors affecting the performance of various natural coagulants on coagulation and flocculation activities as well as the mechanisms governing the process. The recent discoveries on the antimicrobial components and bactericidal ability of several natural coagulants are also included. Since starch has received outstanding attention as a promising coagulant and flocculant, the present paper also discusses the latest progress in starch modification techniques applied to enhance the properties of the material for the application as a water treatment agent. The article also recommends an unconventional method for starch modification to produce a greener and sustainable starch coagulant. In assisting the evaluation of a successful modification procedure, the review also presents the research outcomes on modified starch morphological characterization and physicochemical compositions. The research gaps in the existing literatures and several recommendations are addressed in this work to provide a platform for improvement and establish a new promising direction that can be further explored in the development of starch coagulants as an alternative to chemical coagulants. • The mechanisms and factors governing natural coagulants performance. • Latest works regarding natural coagulants in various water treatment application. • Recent modification techniques to enhance coagulation potential of starch. • Green modification technique is proposed to produce toxicant-free modified starch. • Characterization studies of successfully modified starch are discussed.

Characteristics and Removal Mechanism of an Electro-Hybrid Ozonation-Coagulation System in the Treatment of Organic Matters

To improve the removal efficiency of dissolved organic matter in wastewater treatment plant (WWTP) effluent, electro-hybrid ozonation-coagulation (E-HOC) is proposed and the treatment characteristics and removal mechanism for WWTP effluent and ibuprofen (IBP) are investigated. The E-HOC process has a better removal effect on dissolved organic matter in WWTP effluent, achieving 46.4%, 20.0%, 19.4%, 36.1%, and 49.7% higher removal than EC, ozonation, pre-ozonation-EC, electrocoagulation-ozonation, and chemical coagulation, respectively. To determine the mechanism of the E-HOC process, quenching experiments and electron paramagnetic resonance (EPR) were conducted, which confirmed that metal coagulants can be used as a catalyst to effectively increase the generation of the hydroxyl radical (·OH). Synergistic effects between ozone and the coagulants (SOC) were also found to be involved. Fourier-transform infrared spectroscopy (FT-IR) illustrated that the surface hydroxyl groups of the coagulant (hydrolyzed species produced by Al anode electrolysis) were the active sites for the generation of·OH in the SOC reaction. Based on a kinetics analysis of organic matter removal in the E-HOC system, SOC effects and ozonation played dominant roles in the E-HOC process. Additionally, the SOC created a new pathway for·OH formation.

From Small Molecules Toward Whole Cells Detection: Application of Electrochemical Aptasensors in Modern Medical Diagnostics.

This paper focuses on the current state of art as well as on future trends in electrochemical aptasensors application in medical diagnostics. The origin of aptamers is presented along with the description of the process known as SELEX. This is followed by the description of the broad spectrum of aptamer-based sensors for the electrochemical detection of various diagnostically relevant analytes, including metal cations, abused drugs, neurotransmitters, cancer, cardiac and coagulation biomarkers, circulating tumor cells, and viruses. We described also possible future perspectives of aptasensors development. This concerns (i) the approaches to lowering the detection limit and improvement of the electrochemical aptasensors selectivity by application of the hybrid aptamer–antibody receptor layers and/or nanomaterials; and (ii) electrochemical aptasensors integration with more advanced microfluidic devices as user-friendly medical instruments for medical diagnostic of the future.

Utilization of Alyssum mucilage as a natural coagulant in oily-saline wastewater treatment

Wastewater treatment with natural coagulants is an area that is well-researched and covered in the literature, but new research in this current and ongoing field is still interesting. The present analysis was conducted as the first study to investigate the use of Alyssum mucilage as a new, natural, and cost-effective coagulant for the treatment of synthesized bilge water. To the best of the authors’ knowledge, no previous study has specifically devoted to implementing a systematic analysis of a new coagulant (Alyssum mucilage) within the framework of central composite design-response surface methodology (CCD-RSM), adaptive neuro-fuzzy inference system (ANFIS), and artificial neural network (ANN). Thus, to spot the lights over the mentioned gaps, the current study was undertaken as the first attempt to perform highly comprehensive mathematical, kinetic, and statistical analyses for a quantitative definition of the coagulation-flocculation process of oily-saline wastewater treatment using Alyssum mucilage. In this study, three process-related parameters, such as coagulant dose, contact time, and pH, were introduced for modeling, optimization, and cost analysis of the investigated application. At the optimum conditions (coagulant dose = 40.5 mg/L, pH = 7.05, and contact time = 34.9 min) of Alyssum mucilage, the maximum chemical oxygen demand (COD), turbidity (TU), and surfactant removal efficiencies were obtained as 84.63 %, 96.25 %, and 99 %, respectively. Under the optimum conditions (coagulant dose = 301.8 mg/L, pH = 6.53, and contact time = 23.1 min) of poly aluminum chloride (PAC), used as a comparative polymerized metal coagulant, the maximum COD, TU, and surfactant removal efficiencies were determined as 92.30 %, 99.92 %, and 99 %, respectively. Compared to CCD-RSM, ANFIS and ANN showed high accuracy with R2 values more than 0.990 for both PAC and Alyssum mucilage. The kinetic study revealed that the second-order model performance was superior to the first-order model. Fourier-transform infrared spectroscopy (FTIR) analysis of Alyssum mucilage demonstrated that the functional groups presented in the composition of this coagulant caused coagulation and bonding between the particles. Furthermore, the zeta potentials of bilge water, coagulant, and treated bilge water indicated that the possible mechanism of the coagulation would be adsorption and bridging.

Performance of natural coagulants obtained from agro-industrial wastes in dairy wastewater treatment using dissolved air flotation

Agro-industrial wastes can become organic aids for coagulation, being an alternative to metallic coagulants. In this study ripe okra (Abelmoschus esculentus) and passion fruit (Passiflora edulis) seeds were prepared, characterized and used as natural coagulants in experiments of coagulation/dissolved air flotation (C/DAF) treating synthetic dairy wastewater (SDW). C/DAF was carried out using central composite design (CCD) for optimization of variables. In CCD, the effects of coagulant dosage and pH (independent variables) were studied. Removal of turbidity and chemical oxygen demand (COD) (dependent variables) were evaluated and regression models to predict the removal of these variables were adjusted and validated. The optimum conditions found for removing turbidity and COD were: okra dosage of 2.0 g L−1 at pH 9.00; and passion fruit seeds dosage of 1.3 g L−1 at pH 5.00. Okra as coagulant reduced 91.1 % of turbidity and 48.3 % of COD, whereas passion fruit seeds reduced 91.5 % of turbidity and 50.3 % of COD from the SDW. Okra and passion fruit seeds proved to be promising sources for obtaining coagulant agent, replacing metallic coagulants and minimizing the production of agro-industrial wastes.

Composite method of sewage treatment for chromium ion (VI)

The sewage, containing hexavalent chromium, appears at the different productions, where the main component of technological process is chromic acid. The influence curve has been constructed showing the dependence of the value of the sorption of chromium ions (III) on native bentonite clay. Maximum degree of the treatment is 96.25 % (original concentration is 0.024 mg/ml, minimum degree is 37.63 % (original concentration is 0.481 mg/ml). All the values of residual concentration exceed maximum permissible concentration according to chromium ions. A composite method of sewage treatment of galvanic production for chromium ion (VI) by means of pre-transforming it to chromium ion (III) and adding of bentonite clay and ferric chloride (III) in model solutions has been studied. Ferrum ions after the treatment are not detected in the solution. Optimal mass ratio of metal coagulant to clay in both cases is 1:4000.

Particle aggregation, pH changes and metal behaviour during estuarine mixing: review and integration

Estuaries are dynamic mixing zones where river water interacts with seawater, resulting in large and complex geochemical changes. How two key factors, particle aggregation and pH, affect metal behaviour in estuaries is reviewed and integrated in this paper. Riverine particles are coated with organic matter and electrostatic repulsive forces restrict aggregation. In estuaries, increased concentrations of divalent cations reduce the repulsive forces between particles at low salinities, resulting in their rapid coagulation and removal of particulate-associated metals (e.g. Fe and Pb). However, truly dissolved metals may mix conservatively, and metals associated more with colloidal and dissolved organic material (e.g. Cu and Zn) can show variable behaviour. In many field studies and modelling of river inputs with different compositions, pH decreases slightly at low salinity. Geochemical model simulations of dissolved metal speciation indicated that Zn would be desorbed from iron oxide binding surfaces due to these pH and cation concentration changes, with Cu also showing less binding to dissolved organic matter (DOM). DOM, pH and particle surfaces can influence individual metal behaviour at various spatial and temporal scales. Further integrated field and laboratory research in estuaries where key geochemical processes affecting metal concentrations are measured and modelled is needed.

Aggregating ability of ferric chloride in the presence of phosphate ligand

Complexing anions such as phosphate or silicate play an ambivalent role in the performance of hydrolyzing metal coagulants: On one hand, they significantly interfere with the hydrolytic pathway of conventional iron or aluminum coagulants, the associated destabilization mechanism remaining rather elusive; on the other hand, they have been shown to be key ingredients in the formulation of innovative coagulant solutions exhibiting improved removal efficiency, their action mechanism at the molecular scale being presently poorly understood. In this paper, we explore the effect of small additions of phosphate ligand on the chemical coagulation of silica nanoparticles with ferric chloride. Transmission Electron Microscopy-Energy Dispersed X-ray Spectroscopy (TEM-EDXS) combined with Extended X-ray absorption Fine Structure Spectroscopy (EXAFS) at the Fe K-edge are used to provide an insight into the nature of coagulant species, whereas jar-tests, laser diffraction, Small Angle X-ray Scattering (SAXS), and electrophoretic mobility, are used to investigate the aggregation dynamics of silica particles in the presence of phosphate ligand. We show that, in spite of a slight increase in the consumption of iron coagulant, the addition of phosphate significantly improves the formation of silica aggregates provided that the elemental Fe/P ratio remains above 7. Such effects originate from both a large increase in the overall number of coagulant species, the binding of a phosphate ligand terminating the growth of polymeric chains of edge-sharing Fe octahedra, and a change in the nature of the coagulant species that evolves with the Fe/P ratio, small polycations built-up from Fe-oligomers linked by phosphate tetrahedra being eventually formed. Those non-equilibrium nanosize Fe–P coagulant species assemble the silica nanoparticles to form hetero-aggregates whose structure is consistent with a Diffusion-Limited Cluster Aggregation mechanism.

Effectiveness of chitosan as a natural coagulant in treating turbid waters

Aluminum, Lime and iron coagulants are commonly used in most industries for many decades to coagulate particles in surface water also removing turbidity from the water prior to flocculation, sedimentation or filtration. Although effective, inorganic coagulants have several disadvantages, there has been a concern about the relation between aluminum residuals in treated water and Alzheimer disease and toxic effects of metallic coagulants on the aquatic environment. Hence nowadays, there has been great attention in the improvement of natural coagulants in treated water such as chitosan; chitosan is a natural linear cellulose-like copolymer of glucosamine and N-acetyl-glucosamine widely distributed in nature. The present study was aimed to investigate the effects of chitosan on the removal of suspended solids (bentonite clay) from water. A series of batch flocculation tests with chitosan under different conditions was conducted. The results indicate that chitosan is a potent coagulant for bentonite suspension. Coagulation of chitosan showed efficiency of 96.9%. The coagulant performed well at concentration of 1g chitosan/100 ml water at PH=6.

Promoted chemoselective crotonaldehyde hydrogenation on zirconia-doped SiO2 supported Ag catalysts: Interfacial catalysis over ternary Ag–ZrO2–SiO2 interfaces

In gas-phase chemoselective hydrogenation of crotonaldehyde on Ag-based catalysts, zirconia doping on silica supports was found to improve catalytic performance in terms of unsaturated alcohol selectivity, hydrogenation activity, and stability. The surface modification of silica by zirconia doping favors the fine dispersion of Ag species due to the enhanced quantity and strength of surface acid sites, which enable construction of abundant catalytic sites effective for CO bond hydrogenation. High crotyl alcohol selectivity, exceeding 80%, and significant inhibition of monohydrogenation on the CC bond were observed on the optimal Ag/Zr–SiO2 catalyst. Dynamic O2 chemisorption measurement revealed that the pure Ag powders did not chemisorb O2 irreversibly under 323 K, but SiO2 or Zr–SiO2 supported Ag catalysts did. The amounts of Ag active for O2 chemisorption, which are at least one order of magnitude lower than that of surface Ag derived from TEM and XRD characterizations, match well with the perimeter interface Ag of hemispherical particles. A strong correlation between hydrogenation activity and O2 uptake on those Ag/SiO2 and Ag/Zr–SiO2 catalysts with different Ag dispersions and deactivation degrees was observed, implying that the effective catalytic sites for crotonaldehyde chemoselective hydrogenation may originate from accessible interface sites with unique redox properties. Catalyst induction and deactivation were observed on both Ag/SiO2 and Ag/Zr–SiO2 catalysts in real catalytic operation. Changes in metal stable interface structure, rather than metal aggregation and coagulation, are assumed to be the main cause of irreversible catalyst deactivation, because the apparent Ag particle sizes changed slightly, but the oxygen chemisorption ability deteriorated considerably. Electropositive Ag sites interacting with neighboring oxygen from oxide supports at the ternary Ag–ZrO2–SiO2 interface are proposed to account for highly selective CO bond hydrogenation to produce the desired unsaturated alcohol.

GLYPHOSATE AND TURBIDITY REMOVAL IN WATER CONDITIONS BY CLARIFICATION WITH TANFLOC

With the progress in the agriculture sector, improper domains of pesticides, herbicides, and insecticides have grown, which have been negatively affected the environment until the present day. Therefore, the present work has as objective to evaluate the efficiency of the natural coagulant Tanfloc in the clarification stage with respect the herbicide glyphosate removal and the turbidity parameter by using jar test with different pH conditions and coagulant concentration. As a result, was obtained that for the pH range of 5-5.5 the natural coagulant has shown more efficient, with a glyphosate percentage removal of approximately 98.0% using low concentrations and turbidity removal of 21.69%. On the other hand, for the pH range of 6.8 to 7.3, the coagulant has not shown profitable results, considering that, for some concentrations, it was not possible to detect the herbicide removal. In the concentrations that were detected removal, the average glyphosate percentage removal was approximately 89% and an average of 20.24% of turbidity removal. In summary, although the natural coagulant has not shown remarkably efficient in the neutral pH range, the product may be considered an alternative device in water treatment with the respect of the use of metallic coagulants, which produce sludge with chemistry characteristics that may negatively affect the environment.

Decolorization of reactive dye Remazol Brilliant Blue R by zirconium oxychloride as a novel coagulant: optimization through response surface methodology.

The aim of the present study was to investigate the performance of a novel coagulant, i.e. ZrOCl2, for the removal of anthraquinone-based reactive dye from aqueous solution. An ideal experimental setup was designed based on central composite design using response surface methodology to determine the individual and interactive effects of different operational variables (i.e. pH, coagulant dose and dye concentration) on treatment performance in terms of dye and chemical oxygen demand (COD) removal efficiencies. Total 92.58% dye and 85.33% COD removal were experimentally attained at optimized conditions at low coagulant dose, i.e. 156.67 mg/L for the dye concentration of 105.67 mg/L at pH 2. To validate the working pH of the metal coagulant, the static charge of ZrOCl2 was measured using Eh value. The performance of the coagulant was validated with experimental and predicted values in the selected data set, and R2 values for both responses were found to be 0.99 and 0.95 respectively, which shows the reliability of the experimental design. Further, the toxicity of the coagulant was assessed and no such toxicity was found even up to the concentration of 500 mg/L, proclaiming the disposal of sludge may not exhibit any threat to humans. Experimental results suggested that the ZrOCl2 could be used as an eco-friendly coagulant for dye wastewater treatment.

Cover Image, Volume 93, Issue 2

The cover image, by Jianfeng Li et al., is based on the Research Article Synthesis and optimization of a novel poly‐silicic metal coagulant from coal gangue for tertiary‐treatment of coking wastewater, DOI: 10.1002/jctb.5362. image

REMOVAL OF DYES FROM WATER BY GALVANOCOAGULATION

Galvanocoagulation (GC) utilizing metallic iron chips and granular coke was studied as a potential technique for decolorization of dye-containing aqueous solutions. GC and chemical coagulation by inorganic metallic coagulants such as iron sulfates (Fe2+, Fe3+) were examined for the removal of individual dyes, used in the fur industry, from model aqueous solutions. The role of metal cations when progressively electrogenerated in situ was compared to when they are added simultaneously. The superiority of GC over chemical coagulation was established for the removal of the tested dyes as chemical coagulation required relatively high dosages of coagulant. Additionally, the specific dye removal ability, expressed as q (g/g), which is the maximum amount of dye removed per gram of iron, for GC was considerably higher compared to the one obtained from chemical coagulation. The efficiency of GC was also tested on real wastewater. The average percent removal of chemical oxygen demand (C0D) and color was 90 % and 99%, respectively, during 30 min of treatment. GC is considered a cost-effective and environmentally friendly method which, in the presence of hydrogen peroxide, may also be considered a Fenton-like Process. Using Acid Yellow as a model dye it was observed that the decolorization efficiency increased to 40% when a GC/H202 combination was used as compared to GC alone. UV treatment further increased the efficiency of the GC/H202 system. The dye removal is attributed to both the oxidation by the photo-Fenton reagent and the following adsorption.

Hexavalent chromium removal by monopolar electrodes based electrocoagulation system: optimization through Box–Behnken design

The aim of the present study was to investigate the performance of the graphite and aluminum electrode in monopolar arrangement to assess chromium removal efficiency. The aluminum anode has been used for generation of metal coagulants species, while the cathode material was replaced with monopolar graphite cathode to accomplish a major challenge, i.e., reduce energy consumption and cost of treatment. Moreover, the process has been optimized through the Box–Behnken Design application under response surface methodology by selecting process variables such as current density, pH, process time and a distance between electrodes. The optimized process variables found to be responsible for maximum removal are current density of 2.38 mA/cm 2 , pH of 7.29, process time 23 min, and electrode distance 3.5 cm. It has been found that the power consumed under the optimized condition was low for graphite cathode monopolar arrangement (0.194 kWh/m 3 ) in comparison to aluminum cathode (0.425 kWh/m 3 ) for approximate removal of the hexavalent chromium under similar optimized process variables as applied voltage reduced in the case of graphite cathode due to structural properties and hydrogen adsorption capacity of graphite cathode.

Coagulation of Metals in Superfluid and Normal Liquid Helium.

The thermal emission study in this work has shown that coagulation of metals in liquid helium is accompanied by enormous local overheating of several thousand degrees. Direct experiments demonstrated, for the first time, that condensation of metals in superfluid helium occurs via the specific mechanism which is substantially faster than that in normal liquid helium. It has been stated that coagulation of metals in superfluid helium indeed occurs in two stages, a "hot" one of nanoparticles coalescence with the formation of molten nanospheres and the subsequent stage of their sticking together into nanowires. It turned out that if a laser ablation of metal targets immersed in superfluid helium was used for introducing a metal into liquid, the formation of nanowires occurs at distances of only about 1 mm from the laser focus. This leads to the presence of a considerable number of spherical inclusions in nanowires grown in such a way.

Selective binding behavior of humic acid removal by aluminum coagulation.

The reactivity characteristics of humic acid (HA) with aluminium coagulants at different pH values was investigated. It revealed that the linear complexation reaction occurred between aluminum and humic acid at pH<7, and the reaction rate increased as the pH increased from 2 to 6. While at pH=7, most of the dosed aluminum existed in the form of free aluminum and remained unreacted in the presence of HA until the concentration reached to trigger Al(OH)3(s) formation. Differentiating the change of functional groups of HA by 1H nuclear magnetic resonance spectroscopy and X-ray photoelectron spectra analysis, it elucidated that there was a selective complexation between HA and Al with lower Al dosage at pH 5, which was probably due to coordination of the activated functional groups onto aluminium. While almost all components were removed proportionally by sweep adsorption without selectivity at pH 7, as well as that with higher Al dosage at pH 5. This study provided a promising pathway to analyse the mechanism of the interaction between HA and metal coagulants in future.