Effect of Soil Washing with Ferric Chloride on Cadmium Removal and Soil Structure

In China, arable soils contaminated with cadmium (Cd) threaten human health. Ferric chloride (FeCl3) is a highly efficient agent that can remove Cd from contaminated soils. However, it is unknown whether FeCl3 damages the soil structure and consequently affects crop growth. In this study, we investigated the impacts of Cd extraction by FeCl3 on the structure of a paddy soil on the basis of comparisons of control (without washing agents) and hydrochloric acid (HCl) treatments. According to our results, the removal efficiency increased with the decrease in soil initial pH, as adjusted by FeCl3. However, the low pH of 2.0 caused a partial loss of soil mineral components, with an Al release of 4.4% in the FeCl3-treated soil versus 1.3% in the HCl-treated soil. In contrast, the amount of released Al was less than 0.2% in the control and in the FeCl3 treatments with initial pH values of 3.0 and 4.0. The washing agents caused soil TOC loss of 27.1%, 17.5%, and 2.76% in the pH 2.0, 3.0, and 4.0 FeCl3 treatments, compared with 15.5% in the initial pH 2.0 HCl treatment. The use of FeCl3 represents an optimum tradeoff between removal efficiency and the loss of soil components to restore Cd-polluted soils by adjusting the initial pH to 3.0 with the addition of FeCl3. Under this condition, the amount of Al loss was less than 0.2%, and the extraction efficiency reached 40.3%, compared to an efficiency of 39.7% with HCl at an initial pH of 2.0. In conclusion, FeCl3 could effectively remove Cd from contaminated soil.

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Desorption of Cadmium from Soils Enchanced by Citric Acid

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.610-613.235 ◽

2012 ◽

Vol 610-613 ◽

pp. 235-238

Author(s):

Yu Shuang Li ◽

Xiao Jun Hu ◽

Xue Ying Song

Keyword(s):

Citric Acid ◽

Organic Acids ◽

Toxic Metals ◽

Contaminated Soil ◽

Environmental Problem ◽

Soil Washing ◽

Cadmium Contamination ◽

Cadmium Removal ◽

Citric Acid Concentration ◽

Initial Ph

Cadmium contamination of soil has become a major environmental problem in the whole world. Soil washing is a possible remediation method for extracting contaminants from the contaminated soil. Natural organic acids seem to be promising environmentally friendly for removing toxic metals from soils. Batch soil-washing experiments were conducted to investigate the behavior of cadmium desorption from soils by citric acid. Results showed that cadmium removal by citric acid was highly dependent on the initial pH and the concentration of citric acid. The removal of cadmium declined sharply with the rise of pH. Contrarily, cadmium desorption increased with increasing citric acid concentration. More than 90% cadmium was extracted from soil by 80 mmol L-1 citric acid.

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Chromium and cadmium removal from synthetic wastewater by Electrocoagulation process

Journal of Environmental Treatment Techniques ◽

10.47277/jett/9(2)382 ◽

2020 ◽

Vol 9 (2) ◽

pp. 375-382

Keyword(s):

Removal Efficiency ◽

Current Density ◽

Initial Temperature ◽

Complete Removal ◽

Synthetic Wastewater ◽

Cadmium Removal ◽

Solution Ph ◽

Initial Concentration ◽

Initial Ph ◽

Electrocoagulation Process

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.

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Optimization of aeration enhanced surfactant soil washing for remediation of diesel-contaminated soils using response surface methodology

PeerJ ◽

10.7717/peerj.8578 ◽

2020 ◽

Vol 8 ◽

pp. e8578

Author(s):

Befkadu Abayneh Ayele ◽

Jun Lu ◽

Quanyuan Chen

Keyword(s):

Particle Size ◽

Response Surface Methodology ◽

Organic Matter ◽

Response Surface ◽

Removal Efficiency ◽

Contaminated Soils ◽

Organic Matter Content ◽

Soil Washing ◽

Agitation Speed ◽

Airflow Rate

Surfactant-enhanced soil washing has been used for remediation of organic pollutants for an extended period, but its effectiveness and wide application was limited by the high concentration of surfactants utilized. In this work, the efficiency of conventional soil washing performance was enhanced by 12–25% through the incorporation of air bubbles into the low concentration surfactant soil washing system. Surfactant selection pre-experiment using aerated and conventional soil washing reveals Brij 35 > TX100 > Tween 80 > Saponin in diesel oil removal. Optimization of the effect of time, surfactant concentration, pH, agitation speed, and airflow rate in five levels were undertaken using Response Surface Methodology and Central composite design. The optimum degree of variables achieved was 90 min of washing time, 370 mg/l of concentration, washing pH of 10,535 rpm of agitation speed and 7.2 l/min of airflow rate with 79.5% diesel removal. The high predicted R2 value of 0.9517 showed that the model could efficiently be used to predict diesel removal efficiency. The variation in efficiency of aeration assisted and conventional soil washing was variable depending on the type of surfactant, organic matter content of the soil, particle size distribution and level of pollutant weathering. The difference in removal efficiency of the two methods increases when the level of organic matter increases and when the particle size and age of contamination decreases.

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Efficient Sequestration of Hexavalent Chromium by Graphene-Based Nanoscale Zero-Valent Iron Composite Coupled with Ultrasonic Pretreatment

International Journal of Environmental Research and Public Health ◽

10.3390/ijerph18115921 ◽

2021 ◽

Vol 18 (11) ◽

pp. 5921

Author(s):

Haiyan Song ◽

Wei Liu ◽

Fansheng Meng ◽

Qi Yang ◽

Niandong Guo

Keyword(s):

Aqueous Solution ◽

Removal Efficiency ◽

Inhibitory Effect ◽

Ultrasonic Cavitation ◽

Zero Valent Iron ◽

Ultrasonic Pretreatment ◽

Nanoscale Zero Valent Iron ◽

Passivation Layers ◽

Initial Ph ◽

Two Phases

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.

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Applicability of soil washing method for radionuclide-contaminated soils from road maintenance in Fukushima

Japanese Geotechnical Journal ◽

10.3208/jgs.10.489 ◽

2015 ◽

Vol 10 (4) ◽

pp. 489-502

Author(s):

Osamu TAKAHATA ◽

Shojirou KUMADA ◽

Junya ANDO ◽

Shinji MIYAGUCHI ◽

Koji ISHIYAMA ◽

...

Keyword(s):

Contaminated Soils ◽

Soil Washing ◽

Road Maintenance ◽

Washing Method

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Effects of operational parameters on defluoridation efficiency using electrocoagulation process

Water Practice & Technology ◽

10.2166/wpt.2011.015 ◽

2011 ◽

Vol 6 (1) ◽

Cited By ~ 1

Author(s):

M. Behbahani ◽

M.R. Alavi Moghaddam ◽

M. Arami

Keyword(s):

Reaction Time ◽

Anode Material ◽

Removal Efficiency ◽

Fluoride Concentration ◽

Fluoride Removal ◽

Operational Parameters ◽

Applied Current ◽

Initial Ph ◽

Electrocoagulation Process ◽

Electrode Connection

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.

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Electrocoagulation and nanofiltration integrated process application in purification of bilge water using response surface methodology

Water Science & Technology ◽

10.2166/wst.2016.168 ◽

2016 ◽

Vol 74 (3) ◽

pp. 564-579 ◽

Cited By ~ 11

Author(s):

Ceyhun Akarsu ◽

Yasin Ozay ◽

Nadir Dizge ◽

H. Elif Gulsen ◽

Hasan Ates ◽

...

Keyword(s):

Response Surface Methodology ◽

Response Surface ◽

Removal Efficiency ◽

Cod Removal ◽

Positive Sign ◽

Aluminum Electrode ◽

Integrated Process ◽

Bilge Water ◽

Cod Removal Efficiency ◽

Initial Ph

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.

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A laboratory treatability study for pilot-scale soil washing of Cr, Cu, Ni, and Zn contaminated soils

Environmental Progress & Sustainable Energy ◽

10.1002/ep.10555 ◽

2011 ◽

Vol 31 (3) ◽

pp. 351-360 ◽

Cited By ~ 7

Author(s):

Ya-Ting Lin ◽

Yi-Chi Chien ◽

Chenju Liang

Keyword(s):

Contaminated Soils ◽

Soil Washing ◽

Pilot Scale

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Treatment of simulated printing and dyeing wastewater using ozone microbubble

E3S Web of Conferences ◽

10.1051/e3sconf/202126104005 ◽

2021 ◽

Vol 261 ◽

pp. 04005

Author(s):

Emmanuel Nkudede ◽

Husseini Sulemana ◽

Bo Zhang ◽

Kaida Zhu ◽

Shan Hu ◽

...

Keyword(s):

Mass Transfer ◽

Methylene Blue ◽

Removal Efficiency ◽

Human Life ◽

Cod Removal ◽

Dyeing Wastewater ◽

Flow Rates ◽

Printing And Dyeing Wastewater ◽

Cod Removal Efficiency ◽

Initial Ph

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.

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