scholarly journals The Effect of Fe(II), Fe(III), Al(III), Ca(II) and Mg(II) on Electrocoagulation of As(V)

Water ◽  
2022 ◽  
Vol 14 (2) ◽  
pp. 215
Author(s):  
Niels Michiel Moed ◽  
Young Ku

The interaction between metal chlorides and electrocoagulation was tested. Precipitation of As(V) was found to be optimal at pH 4.9 using FeCl2, 2.6 for FeCl3, 3.8 using AlCl3, 11.6 using CaCl2 and 8.6 using MgCl2. As(V) removal through electrocoagulation went down as initial pH (pHi) of the solution increased. Addition of FeCl2 increased removal of As(V) at all pHi but was not able to achieve full removal at pHi 7. FeCl3 had a similar effect but a lower Fe(III) concentration of 30 mg/L was not sufficient for full removal at pHi 5 either. AlCl3 addition reduced removal efficiency at pHi 3 but removed all or most As(V) through precipitation at pHi 5 and 7, with complete removal followed through electrocoagulation. The addition of CaCl2 and MgCl2 resulted in nearly identical behavior. Addition of either at pHi 3 had no influence, but at pHi 5 and 7 caused complete removal to take place.

2017 ◽  
Vol 2017 ◽  
pp. 1-10 ◽  
Author(s):  
Zhitao Han ◽  
Bojun Liu ◽  
Shaolong Yang ◽  
Xinxiang Pan ◽  
Zhijun Yan

The experiments were performed in a lab-scale countercurrent spraying reactor to study the NOxremoval from simulated gas stream by cyclic scrubbing using NaClO solution. The effects of NaClO concentration, initial solution pH, coexisting gases (5% CO2and 13% O2), NOxconcentration, SO2concentration, and absorbent temperature on NOxremoval efficiency were investigated in regard to marine exhaust gas. When NaClO concentration was higher than 0.05 M and initial solution pH was below 8, NOxremoval efficiency was relatively stable and it was higher than 60%. The coexisting CO2(5%) had little effect on NOxremoval efficiency, but the outlet CO2concentration decreased slowly with the initial pH increasing from 6 to 8. A complete removal of SO2and NO could be achieved simultaneously at 293 K, initial pH of 6, and NaClO concentration of 0.05 M, while the outlet NO2concentration increased slightly with the increase of inlet SO2concentration. NOxremoval efficiency increased slightly with the increase of absorbent temperature. The relevant reaction mechanisms for the oxidation and absorption of NO with NaClO were also discussed. The results indicated that it was of great potential for NOxremoval from marine exhaust gas by wet scrubbing using NaClO solution.


2020 ◽  
Vol 9 (2) ◽  
pp. 375-382

Electrocoagulation (EC) is one of the efficient electrochemical approaches for industrial wastewater treatment. The present work aims to reach optimum conditions for achieving simultaneous removal of chromium and cadmium ions from synthetic wastewater by EC through assessment of different parameters like electrodes material, electrode configuration, initial pH, current density, initial temperature, and initial contaminate concentration. In addition, a comparison between chemical coagulation and EC efficiency for Chromium and cadmium removal was presented. Results showed that the (Fe-Al), an anode and cathode, achieved better removal efficiency than other electrodes configurations (Fe-Fe / Al-Fe / Al- Al). Also, the increase of initial temperature and current density enhanced the removal efficiency. In contrast, the increase in the initial concentration reduced the removal efficiency. The complete removal of Chromium achieved through the use of Fe-Al electrodes and current density was 12.50 mA/cm2 with solution pH of 5.8, temperature was 25oC and an initial concentration of 280 mg/L. On the other hand, Cadmium’s complete removal was achieved through the use of Fe-Allectrodes, at pH of 5.8, applied current 1.4 A and 60oC. Therefore, EC was proved to be better approach than conventional coagulation in case of treatment of wastewater containing different types of heavy metals ions with high initial concentrations.


2004 ◽  
Vol 4 (5-6) ◽  
pp. 335-341 ◽  
Author(s):  
Jae-Kyu Yang ◽  
Yoon-Young Chang ◽  
Sung-Il Lee ◽  
Hyung-Jin Choi ◽  
Seung-Mok Lee

Iron-coated sand (ICS) prepared by using FeCl3 and Joomoonjin sand widely used in Korea was used in this study. In batch adsorption kinetics, As(V) adsorption onto ICS was completed within 20 minutes, while adsorption of Pb(II), Cd(II), and Cu(II) onto ICS was slower than that of As(V) and strongly depended on initial pH. At pH 3.5, ICS showed a selective adsorption of Pb(II) compared to Cd( II) and Cu(II) . However, above pH 4.5, near complete removal of Pb(II), Cd(II), and Cu(II) was observed through adsorption or precipitation depending on pH. As(V) adsorption onto ICS occurred through an anionic-type and followed a Langmuir-type adsorption behaviour. In column experiments, pH was identified as an important parameter in the breakthrough of As(V). As(V) breakthrough at pH 4.5 was much slower than at pH 9 due to a strong chemical bonding between As(V) and ICS as similar with batch adsorption behaviour. With variation of ICS amounts, the optimum amount of ICS at pH 4.5 was identified as 5.0 grams in this research. At this condition, ICS could be used to treat 200 mg of As(V) with 1 kg of ICS until 50 ppb of As(V) appeared in the effluent. In this research, as a new treatment system, ICS can be potentially used to treat As(V) and cationic heavy metals.


Author(s):  
Haiyan Song ◽  
Wei Liu ◽  
Fansheng Meng ◽  
Qi Yang ◽  
Niandong Guo

Nanoscale zero-valent iron (nZVI) has attracted considerable attention for its potential to sequestrate and immobilize heavy metals such as Cr(VI) from an aqueous solution. However, nZVI can be easily oxidized and agglomerate, which strongly affects the removal efficiency. In this study, graphene-based nZVI (nZVI/rGO) composites coupled with ultrasonic (US) pretreatment were studied to solve the above problems and conduct the experiments of Cr(VI) removal from an aqueous solution. SEM-EDS, BET, XRD, and XPS were performed to analyze the morphology and structures of the composites. The findings showed that the removal efficiency of Cr(VI) in 30 min was increased from 45.84% on nZVI to 78.01% on nZVI/rGO and the removal process performed coupled with ultrasonic pretreatment could greatly shorten the reaction time to 15 min. Influencing factors such as the initial pH, temperature, initial Cr(VI) concentration, and co-existing anions were studied. The results showed that the initial pH was a principal factor. The presence of HPO42−, NO3−, and Cl− had a strong inhibitory effect on this process, while the presence of SO42− promoted the reactivity of nZVI/rGO. Combined with the above results, the process of Cr(VI) removal in US-nZVI/rGO system consisted of two phases: (1) The initial stage is dominated by solution reaction. Cr(VI) was reduced in the solution by Fe2+ caused by ultrasonic cavitation. (2) In the following processes, adsorption, reduction, and coprecipitation coexisted. The addition of rGO enhanced electron transportability weakened the influence of passivation layers and improved the dispersion of nZVI particles. Ultrasonic cavitation caused pores and corrosion at the passivation layers and fresh Fe0 core was exposed, which improved the reactivity of the composites.


2011 ◽  
Vol 6 (1) ◽  
Author(s):  
M. Behbahani ◽  
M.R. Alavi Moghaddam ◽  
M. Arami

The aim of this study is to examine the effect of operational parameters on fluoride removal using electrocoagulation method. For this purpose, various operational parameters including initial pH, initial fluoride concentration, applied current, reaction time, electrode connection mode, anode material, electrolyte salt, electrolyte concentration, number of electrodes and interelectrode distance were investigated. The highest defluoridation efficiency achieved at initial pH 6. In the case of initial fluoride concentration, maximum removal efficiency (98.5%) obtained at concentration of 25mg/l. The increase of applied current and reaction time improved defluoridation efficiency up to 99%. The difference of fluoride removal efficiencies between monopolar and bipolar series and monopolar parallel were significant, especially at reaction time of 5 min. When aluminum used as anode material, higher removal efficiency (98.5%) achieved compared to that of iron anode (67.7%). The best electrolyte salt was NaCl with the maximum defluoridation efficiency of 98.5% compared to KNO3 and Na2SO4. The increase of NaCl had no effect on defluoridation efficiency. Number of electrodes had little effect on the amounts of Al3+ ions released in the solution and as a result defluoridation efficiency. Almost the same fluoride removal efficiency obtained for different interelectrode distances.


2008 ◽  
Vol 57 (5) ◽  
pp. 715-720 ◽  
Author(s):  
S. Quinzaños ◽  
C. Dahl ◽  
R. Strube ◽  
R. Mujeriego

Irrigation with reclaimed water is becoming a practical alternative to conventional irrigation in semi-arid areas of the Mediterranean like Spain, but it requires a reliable treatment process to provide a safe water supply. Helminth eggs are one of the main concerns for the safe use of reclaimed water, as they can survive adverse environmental conditions and they are highly infective. Spanish water quality criteria and International guidelines set a limit of 0.1 eggs/l for water uses with unrestricted human exposure. Two microscreening processes have been tested to determine their potential for helminth eggs removal, after a conventional physic-chemical reclamation process. Hydrotech Drum and Discfilters®, provided with 10 μm pore size filter cloth, were tested to determine their efficiency for helminth eggs straining. An experimental test was conducted using 20 μm spherical latex particles, as surrogates for helminth eggs, to test the removal efficiency of a small full-scale drumfilter. In a subsequent laboratory test, actual Trichuris suis eggs were strained using a 10 μm pore size filter cloth from a discfilter. Results from both tests indicate that drum and discfilters are able to achieve 99% removal efficiency for spherical latex particles and a complete removal for helminth eggs in reclaimed water.


2016 ◽  
Vol 74 (3) ◽  
pp. 564-579 ◽  
Author(s):  
Ceyhun Akarsu ◽  
Yasin Ozay ◽  
Nadir Dizge ◽  
H. Elif Gulsen ◽  
Hasan Ates ◽  
...  

Marine pollution has been considered an increasing problem because of the increase in sea transportation day by day. Therefore, a large volume of bilge water which contains petroleum, oil and hydrocarbons in high concentrations is generated from all types of ships. In this study, treatment of bilge water by electrocoagulation/electroflotation and nanofiltration integrated process is investigated as a function of voltage, time, and initial pH with aluminum electrode as both anode and cathode. Moreover, a commercial NF270 flat-sheet membrane was also used for further purification. Box–Behnken design combined with response surface methodology was used to study the response pattern and determine the optimum conditions for maximum chemical oxygen demand (COD) removal and minimum metal ion contents of bilge water. Three independent variables, namely voltage (5–15 V), initial pH (4.5–8.0) and time (30–90 min) were transformed to coded values. The COD removal percent, UV absorbance at 254 nm, pH value (after treatment), and concentration of metal ions (Ti, As, Cu, Cr, Zn, Sr, Mo) were obtained as responses. Analysis of variance results showed that all the models were significant except for Zn (P > 0.05), because the calculated F values for these models were less than the critical F value for the considered probability (P = 0.05). The obtained R2 and Radj2 values signified the correlation between the experimental data and predicted responses: except for the model of Zn concentration after treatment, the high R2 values showed the goodness of fit of the model. While the increase in the applied voltage showed negative effects, the increases in time and pH showed a positive effect on COD removal efficiency; also the most effective linear term was found as time. A positive sign of the interactive coefficients of the voltage–time and pH–time systems indicated synergistic effect on COD removal efficiency, whereas interaction between voltage and pH showed an antagonistic effect.


1993 ◽  
Vol 50 (1) ◽  
pp. 154-156 ◽  
Author(s):  
H. Fonseca ◽  
M.A.B. Regitano-d'Arce

A preliminary approach to achieve compatible simultaneous extraction of aflatoxin and residual oil from pressed oil meals was conducted to determine the minimum amount of water to be added to ethanol versus necessary time to achieve complete removal of aflatoxin. Commercial anhydrous, 96, 93 and 90°GL ethanol were utilized in trials with Soxhlet extractors. Commercial anhydrous ethanol did not remove aflatoxin completely and the extraction efficiency in minutes was directly proportional to the amount of water present in the ethanol, as expected. Although 96°GL ethanol was efficient, alcoholic strengths between 96 and 99°GL need be evaluated to improve oil extraction, provided they do not decrease aflatoxin removal efficiency.


2021 ◽  
Vol 261 ◽  
pp. 04005
Author(s):  
Emmanuel Nkudede ◽  
Husseini Sulemana ◽  
Bo Zhang ◽  
Kaida Zhu ◽  
Shan Hu ◽  
...  

Owing to its widespread and persistent usage, methylene blue (MB) is an environmental substance, mostly found in the printing and dyeing industry that raises concerns in the environment recently by posing significant threat to human life and the ecosystem as a whole. Thus, there is the need to effectively manage and treat the wastewater from these industries before reaching to the available water sources. Ozonation treatment is very efficient in treating printing and dyeing wastewater (MB) and can be greatly improved by using micro-bubble technology. Microbubble dissolution is an effective way to improve the rate of ozone mass transfer. To discover these properties, a method was used to improve the mass transfer of ozone microbubbles, which was used to effectively treat simulated printing and dyeing wastewater. We investigated the effects of pH, water temperature, ozone flow, and other conditions on the dissolution and attenuation properties of ozone in methylene blue microbubble solutions. Treatment of simulated printing and dyeing wastewater (methylene blue) was investigated under various initial pH and ozone flow rates. A catalytic exhibition was performed towards the decolorization of methylene blue (MB) concentrations and the corresponding COD removal efficiency. Ozone depletion and pH levels played key roles in MB degradation. Under high pH level of 11.01, the rate of removal of COD was 93.5%. Ozone dosage also has direct effect on COD removal efficiency and decolorization. Higher ozone flow rates, 0.4 L/min and 0.5 L/min recorded more than 94% degradation of COD thus very effective and efficient. Also, ozone flow rates 0.3 L/min, 0.4 L/min and 0.5 L/min with initial pH, 7.03, 6.63 and 6.36 decreased to 3.43, 3.49 and 3.44 after reaction processes which clearly shows that with high ozone dosage, pH reduces considerably.


2021 ◽  
Vol 900 (1) ◽  
pp. 012003
Author(s):  
M Balintova ◽  
Z Kovacova ◽  
S Demcak ◽  
Y Chernysh ◽  
N Junakova

Abstract Removal of heavy metals from the environment is important for living beings. The present work investigates the applicability of the natural and MnO2 - coated zeolite as sorbent for the removal of copper from synthetic solutions. Batch experiments were carried out to identify the influence of initial pH and concentration in the process of adsorption. A maximum removal efficiency of Cu(II) was observed in 10 mg/L for natural (95.6%) and modified (96.4%) zeolite, where the values was almost identical, but at concentration of 500 mg/L was the removal efficiency of modified zeolite three times higher. Based on the correlation factors R2, the Langmuir isotherms better describe the decontamination process than Freundlich. The optimum pH value was set at 5.0.


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