scholarly journals Preparation of Activated Carbon Supported Bead String Structure Nano Zero Valent Iron in a Polyethylene Glycol-Aqueous Solution and Its Efficient Treatment of Cr(VI) Wastewater

Molecules ◽  
2019 ◽  
Vol 25 (1) ◽  
pp. 47 ◽  
Author(s):  
Chunlei Jiao ◽  
Xiao Tan ◽  
Aijun Lin ◽  
Wenjie Yang
Keyword(s):  
Activated Carbon ◽  
Polyethylene Glycol ◽  
Removal Rate ◽  
Zero Valent Iron ◽  
Efficient Treatment ◽  
Removal Capacity ◽  
Oxidation Reduction ◽  
String Structure ◽  
Nano Zero Valent Iron ◽  
Reduction Effect

Nanometer zero-valent iron (nZVI) has been widely used in the treatment of heavy metals such as hexavalent chromium (Cr(VI)). A novel composite of bead string-structured nZVI on modified activated carbon (nZVI–MAC) is prepared here, using polyethylene glycol as the stable dispersant rather than traditional ethanol during the loading process. The microstructure characterization shows that nZVI particles are loaded on MAC with a bead string structure in large quantity and stably due to the addition of hydroxyl functional groups on the surface by polyethylene glycol. Experiments on the treatment of Cr(VI) in wastewater show that the reaction process requires only 20 min to achieve equilibrium. The removal rate of Cr(VI) with a low concentration (80–100 mg/L) is over 99% and the maximum saturation removal capacity is up to 66 mg/g. The system converts Cr(VI) to trivalent chromium (Cr(III)) through an oxidation-reduction effect and forms an insoluble material with iron ions by coprecipitation, which is then adsorbed on the surface of the nZVI–MAC. The process conforms to the quasi-second order adsorption kinetics equation (mainly chemical adsorption process).

scholarly journals Size Distribution and Phosphate Removal Capacity of Nano Zero-Valent Iron (nZVI): Influence of pH and Ionic Strength

Water ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2939
Author(s):  
Dantong Lin ◽  
Liming Hu ◽  
Irene M. C. Lo ◽  
Zhigang Yu
Keyword(s):  
Ionic Strength ◽  
Size Distribution ◽  
Environmental Conditions ◽  
Colloidal Stability ◽  
Removal Rate ◽  
Phosphate Removal ◽  
Zero Valent Iron ◽  
Removal Capacity ◽  
Nano Zero Valent Iron ◽  
Ph Conditions

Nano zero-valent iron (nZVI) has been considered as a promising material for groundwater remediation in the past few decades. The size distribution of nZVI is one of the main factors that influences its transport capability and remediation capacity. However, studies on the size distribution of nZVI under different environmental conditions are still limited. In this study, the influence of the pH (pH = 5, 7, 9) and ionic strength (IS = 0, 15, 30, 45 mM) on the size distribution of nZVI are investigated. The dynamic light scattering (DLS) method is used to study the variation of the size distribution of nZVI aggregate with time, and batch tests are performed to evaluate the efficiency of phosphate removal. Meanwhile, the phosphate removal capacity of nZVI with different size distribution was examined. Experimental results show that under low IS and high pH conditions, nZVI aggregate exhibited a stable, narrow and one-peak size distribution. By contrast, under high IS and low pH conditions, nZVI exhibited a wide and complicated size distribution with multiple peak values. This different pattern in size distribution was further explained by the Derjaguin–Landau–Verwey–Overbeek (DLVO) theory. The phosphate removal rate of nZVI under acidic and neutral conditions is higher than 98% but is only 68% under alkaline conditions. The phosphate removal capacity is insensitive to the variation of IS since the removal rate is higher than 97% for different IS conditions. Favorable environmental conditions for colloidal stability and removal capacity of nZVI can be different, which needs comprehensive consideration in the application.

Biological treatment characteristics of benzene and toluene in a biofilter packed with cylindrical activated carbon

2002 ◽  
Vol 46 (11-12) ◽  
pp. 51-56 ◽  
Author(s):  
G.-W. Li ◽  
H.-Y. Hu ◽  
J.-M. Hao ◽  
H.-Q. Zhang
Keyword(s):  
Carbon Dioxide ◽  
Activated Carbon ◽  
Gas Flow ◽  
Removal Rate ◽  
Carbon Dioxide Concentration ◽  
Organic Load ◽  
Filler Materials ◽  
Removal Capacity ◽  
Bacillus Spore ◽  
Maximum Removal

The biodegradation of toluene and benzene in a biofilter using cylindrical activated carbon as the filler materials was studied. Three gas flow rates, i.e. 0.25, 0.50 and 0.75 m3/h, corresponding to empty bed gas residence of 75, 37.5 and 25 s, respectively, and total organic load lower than 400 g/m3.h were tested. The biofilter proved to be highly efficient in biodegradation of toluene and benzene, and toluene was more easily degraded than benzene. When each inlet load was lower than 150 g/m3.h, removal rate increased with inlet load and reached a maximum, which was 150 and 120 g/m−3.h for toluene and benzene, respectively. For inlet load higher than the maximum removal capacity conditions, the removal rate decreased with inlet load. Carbon dioxide concentration profile through the biofilter revealed that the mass ratios of carbon dioxide produced to the toluene and benzene removed were 2.15 g(CO2)/g(toluene) and 1.67 g(CO2)/g(benzene), which furthermore, confirmed the biodegradation performance in biofilter. The observation of biotic community demonstrated that the microbes consisted of bacillus, spore bacillus and fungi, of which the spore bacillus was dominant.

scholarly journals Ultra-Highly Efficient Removal of Methylene Blue Based on Graphene Oxide/TiO2/Bentonite Sponge

Materials ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 824
Author(s):  
Yuan Liu ◽  
Luyan Wang ◽  
Ni Xue ◽  
Pengxiang Wang ◽  
Meishan Pei ◽  
...  
Keyword(s):  
Methylene Blue ◽  
Graphene Oxide ◽  
Removal Rate ◽  
Cost Effective ◽  
Electron Hole ◽  
Efficient Treatment ◽  
Highly Efficient ◽  
Removal Capacity ◽  
Sensitivity Range

An ultra-highly efficient Graphene Oxide/TiO2/Bentonite (GO/TiO2/Bent) sponge was synthesized using an in situ hydrothermal method. GO/TiO2/Bent sponge with a GO mass concentration of 10% exhibited the highest treatment efficiency of methylene blue (MB), combining adsorption and photocatalytic degradation, and achieved a maximum removal efficiency of 100% within about 70 min. To further prove the ultra-high removal capacity of the sponge, the concentration of MB in water increased to ten times the original concentration. At so high a MB concentration, the removal rate was still as high as 80% in 90 min. The photocatalytic mechanism of GO/TiO2/Bent sponge was discussed through XPS, PL and radicals quenching experiments. Here Bent can immobilize TiO2 and react with a photo-generated hole to increase the amount of hydroxyl radical; effectively enhancing the degradation of MB.GO sponge enlarges the sensitivity range of TiO2 to visible light by increasing the charge separation of TiO2 and reducing the recombination of photo-generated electron–hole pairs. Additionally, GO sponge with an interconnected porous structure provides an effective platform to immobilize TiO2/bent and makes them be easily recovered. The as-prepared sponge develops a simple and cost-effective strategy to realize the ultra-highly efficient treatment of dyes in wastewater.

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