Dear Renu Bisht

According to my researches pH= 5.3-5.8 was the best range for removing Cadmium.

Regards

Dear Renu Bisht

According to my researches pH= 5.3-5.8 was the best range for removing Cadmium.

Regards

Please check the following links and PDF attachments.

https://www.researchgate.net/publication/221855652_Copper_and_cadmium_removal_from_synthetic_industrial_wastewater_using_chitosan_and_nylon_6

https://www.researchgate.net/post/How_pH_effect_the_electrocoagulation_process_in_waste_water_treatment

https://www.researchgate.net/figure/26473781_fig6_Figure-6-Cadmium-removal-at-pH-3-6

https://www.researchgate.net/publication/260163478_Copper_lead_and_cadmium_removal_by_Ca_Al_layered_double_hydroxides

https://www.researchgate.net/figure/281555320_fig1_Fig-1-Effect-of-solution-pH-on-adsorption-of-cadmium-ions-on-coffee-grounds-and-wheat

http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322010000200008

Article Copper and cadmium removal from synthetic industrial wastewa...

Article Copper, lead and cadmium removal by Ca Al layered double hydroxides

Dear colleague

You must consider other factors (including:the clay mineralogy, CEC, Organic matter content, and specific surface area, calcareous soil and ...), because this parameters influence on  the adsorption of Cd from soil solution to soils. therefore, The relationships of Cd with those parameters and Cd adsorption in soils is affected by the soil characteristics.

Dear Renu Bisht, 

The removal percentage depends on many factors especially your adsorbent or your studied technique. Please, have a look to the following papers

Hello, I can not see from you chart what kind of conditions have you construct to measure this. The pH is one of the important parameters but it is strongly dependent on presence of other ions in the solution. Also it depends on other particles such as organic compounds etc. When you have a solution of all nutrient salts, with other compounds usually present in the soil,  then you would have Cd precipitation occurring at higher alkali pH, resulting in reduced solubility and thus decreased bio availability... 

You did not provide enough information with your Figure to sort out what you saw. How much Cd was in the test soil? Was it spiked? spiked Cd is much more readily released to solution than long equilibrated Cd. In other research, Cd is increasingly extracted by 0.01 M Ca(NO3)2 with lower pH. It is conceivable that at high pH, say 8 and above, in high OM soil, that some Cd-OM can be leached, like higher Cu leaching at higher pH due to dissolution of OM at higher pH. But Cd is usually continuously increasintly soluble at lower pH.

And finding even 10% extracted was a little unusual unless you were testing a sand soil.

Also,

  it is not mentioned what method and what process is used to remove cadmium.

Regards

Jan

Dear Renu Bisht

The pH value is one of crucial parameters which influence the efficiency of the process of cadmium uptake

Higher concentrations are usually removed by precipitation as metal hydroxides: at pH>7 the precipitation of cadmium hydroxide takes place.

Lower concentrations can be removed by adsorption, ion exchange, and different membrane techniques: at pH

Usually optimum pH for cadmium removal is pH 5.0-6.0. It has been mentioned in literatures that prevalence of free cadmium ions at pH below 8.0 after which hydroxyls are formed which may hinder adsorption....so i think removal may increase even after pH 6.0 as well.....you can consult paper ....Journal of Hazardous Materials 164 (2009) 161–171.

The chemistry of most soil is pH dependent. In this case however, detailed information about the soil, vis-a-vis, the SOM, clay mineralogy and particle size distribution are yet to be given. One known fact is that as soil pH value increases, metals solubility and availability generally reduced. 

In such investigations, soil pHH2O and pHKCl, and deltapH should be analysized in soil as well as its CEC, besides all important parameters given above.

Dear Renu Bisht:

I think you did not tell us enough about your system to let us offer helpful information. Re-reading your note, I now imagine that you are trying to remove Cd from a solution of some kind by precipitation. This model is complex because any chloride in the solution can form complexes with Cd and increase solubility of Cd at neutral to alkaline pH. And at very high pH, hydroxy complexes can increase solubility of Cd and Zn.

Long ago we were trying to show that industry could remove Cd from wastewaters from Cd plating, after they destroyed the cyanide used in the plating baths. Some had been claiming that one could not remove Cd from these solutions well enough to lower Cd in their wastewater discharged to sewers to protect the quality of the biosolids produced by a major city. So we tested a simple system using commercial peat, and an artificial wastewater. And higher pH, 7+, to minimize Cd binding by the peat. We used a column of peat and removed the Cd essentially quantitatively. There was some color in the discharge from dissolved organic matter from the peat, and it is likely that a little Cd was moving thru the column as complexes with the low MS peat materials. But we did show that the discharge from a simple wastewater treatment system could prevent Cd discharge to the sewer and protect biosolids.

In my earlier post, I assumed that you were working with soil and removal would increase with pH up to about 10, and chloride in the water could increase Cd solubility.

Hope this helps,

Rufus Chaney