Co-removal of Hexavalent Chromium through Copper Precipitation in Synthetic Wastewater

2003 ◽  
Vol 37 (18) ◽  
pp. 4281-4287 ◽  
Author(s):  
Jing-Mei Sun ◽  
Chii Shang ◽  
Ju-Chang Huang
Keyword(s):  
Hexavalent Chromium ◽  
Synthetic Wastewater ◽  
Copper Precipitation ◽  
Co Removal

Co-removal of hexavalent chromium through adsorption during copper precipitation

2004 ◽  
Vol 50 (8) ◽  
pp. 201-208 ◽  
Author(s):  
J.M. Sun ◽  
J.C. Huang
Keyword(s):  
Hexavalent Chromium ◽  
Ligand Exchange ◽  
Pure Copper ◽  
Chemical Precipitation ◽  
Divalent Copper ◽  
Surface Loading ◽  
Copper Precipitation ◽  
Batch Tests ◽  
Co Removal ◽  
Precipitation Phenomena

A systematic study was conducted to assess the mechanisms involved in the co-removal of hexavalent chromium during chemical precipitation of divalent copper. Batch tests were used to assess the precipitation phenomena in both pure copper solutions and also mixed copper-Cr(VI) solutions with progressive addition of sodium carbonate to increase pH and induce precipitation. It was found that the coremoval of Cr(VI) was caused by two distinct mechanisms: coprecipitation of copper with Cr(VI) at pH 5.0 to 5.2, leading to the formation of CuCrO4 precipitates. Once the fine crystallites of CuCrO4 were formed, the test solution became heterogeneous and this accelerated the production of copper-carbonate precipitates, mainly in the form of CuCO3·Cu(OH)2, at pH 5.2 to 6.2. The latter precipitates were negatively charged at pH below 7.5, and thus they were able to adsorb a considerable amount of the remaining chromate ions [HCrO4- and CrO42-]. The extent of adsorption depended on both pH and surface loading. Besides electrostatic attraction, ligand exchange was also found to play some role. Maximum adsorption occurred at pH 6.5. When pH was raised to 10.0, approximately 25-30% of the adsorbed chromium could become desorbed due to a surface charge reversal on the adsorbent.

Characterization of adsorbent composition in co-removal of hexavalent chromium with copper precipitation

Chemosphere ◽  
2005 ◽  
Vol 58 (8) ◽  
pp. 1003-1010 ◽  
Author(s):  
Jing-Mei Sun ◽  
Xin-Hua Zhao ◽  
Ju-Chang Huang
Keyword(s):  
Hexavalent Chromium ◽  
Copper Precipitation ◽  
Co Removal

Co-removal of hexavalent chromium during copper precipitation

2002 ◽  
Vol 46 (4-5) ◽  
pp. 413-419 ◽  
Author(s):  
J. Sun ◽  
J.-C. Huang
Keyword(s):  
Hexavalent Chromium ◽  
Pure Copper ◽  
Molar Ratio ◽  
Chromium Removal ◽  
Copper Carbonate ◽  
Potential Measurement ◽  
Copper Precipitation ◽  
Batch Tests ◽  
Co Removal ◽  
Co Precipitation

In our recent study using the nucleated precipitation technology to treat plating wastewater, it was found that about one half of hexavalent chromium was co-removed with copper, nickel and zinc. Since hexavalent chromium could not react with either hydroxide or carbonate to from precipitates, this study was undertaken to evaluate the mechanism(s) involved in the chromium co-removal. Batch tests were conducted with synthetic solutions containing either only copper or both copper and hexavalent chromium. Metal precipitation was induced by adding Na2CO3 to different pH, and the quantitative removal of copper and chromium was determined. Besides, the [Cr]/[Cu] molar ratio of produced precipitates were also assessed in conjunction with the EDAX analysis to determine their compositions. Experimental results indicate that for pure copper solution, precipitation begins at pH 6.0, and completes at pH 7.0. The chemical forms of the precipitates are copper carbonates [CuCO3.Cu(OH)2 and CuCO3.2Cu(OH)2]. On the other hand, in a bi-metal solution of copper plus chromium, precipitation of copper begins at about pH 5.0, and copper precipitation is always accompanied by some chromium removal. From the removal stoichiometry of the two metals, it is found that at low pH, the co-removal is a result of “co-precipitation” which results in the formation of CuCrO4 crystallites. Once such crystallites are formed, they provide a heterogeneous environment which enhances an early formation of copper carbonate at a lower pH (below 5.5). It is further found that once copper carbonate precipitates are produced, the remaining soluble will precipitate in such form, and at this stage further removal of copper is no longer accompanied by additional chromium removal. The test data also reflect that the produced copper carbonates are positively charged, as verified by zeta potential measurement, at pH below 7.5. Thus they are able to adsorb some anionic chromium (existing as chromate) through electrostatic attraction and/or inorganic ligand exchange. At pH of 6 to 10, the extent of adsorption decreases with increasing pH, and the adsorption capacity seems to coincide with the progressive reduction of positive zeta potentials of the precipitated particles.

scholarly journals Removal of Hexavalent Chromium from Synthetic Wastewater Using Alginate Immobilized Cyanobacteria: Experiment and Mathematical Modeling

2020 ◽  
Vol 37 (4) ◽  
pp. 283-294
Author(s):  
Sushovan Sen ◽  
Abhishek Dutta ◽  
Rambabu Ponnala ◽  
Biswajit Kamila ◽  
Pranas Baltrėnas ◽  
...  
Keyword(s):  
Mathematical Modeling ◽  
Hexavalent Chromium ◽  
Synthetic Wastewater

scholarly journals Performance of Laterite Soil Grains as Adsorbent in the Removal of Chromium

2015 ◽  
Vol 10 (1) ◽  
pp. 270-280 ◽  
Author(s):  
I Syama ◽  
Arun Thalla ◽  
D Manu
Keyword(s):  
Hexavalent Chromium ◽  
Removal Efficiency ◽  
Freundlich Isotherm ◽  
Synthetic Wastewater ◽  
Batch Adsorption ◽  
Ferric Ion ◽  
Column Studies ◽  
Adsorbent Dosage ◽  
Adsorbate Concentration ◽  
Percentage Removal

The present study aims to examine the efficiency of laterite grains (LG) and acid activated laterite grains (AALG) as an adsorbent for removal hexavalent chromium and ferric ion from synthetic wastewater, under laboratory conditions. Adsorption of hexavalent chromium and ferric ion from synthetic wastewater is examined by batch and column studies wherein it is found to be dependent on pH, Contact time, adsorbent dosage and initial adsorbate concentration. Percentage removal enhances with the increase in adsorbent dosage and with low pH, the optimal removal is achieved at pH=2. AALG is found to investigate possibility of improvement in removal efficiency of hexavalent chromium. The removal efficiency of AALG is found to be significantly higher than the efficiency obtained from LG, at pH=7. An adsorbent dosage 2g of LG is found to be optimum for removal of ferric ion with low initial concentration of 2.5 mg/L. The equilibrium adsorption data obtained from batch studies were fitted with Langmuir and freundlich isotherm for both hexavalent chromium and ferric ions. The percentage removal obtained from batch adsorption studies were found to be higher than that obtained by column studies for both the adsorbates.

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