Cadmium Removal Processes in the Environment Dana Weatherby

Cadmium Removal Processes in the Environment Dana Weatherby, Gabriela Webb, and Melissa Valencia

What is Cadmium? ● ● ● Rare, but toxic element found in nature Found first in zinc carbonate, which was being used as zinc oxide in 1817 Refined during zinc production Occurs in association with Zinc Common uses: ○ Nickel-cadmium batteries (rechargeable) ○ Cell phones ○ Cordless power tools ○ Cameras ○ Other cordless electronics NOAEL for humans is 0. 01 mg/kg/day

How does it end up in the environment? ● Burning of fossil fuels ● Incineration of municipal waste ○ ○ ○ Nickel Cadmium batteries Other plastics Pigments ● Smelting

Soil Remediation 3 common methods: ● Excavation ○ ○ physical removal oldest method ● Stabilization ○ ○ ○ eliminating bioavailability AKA in situ fixation If amendments added above ground: ex situ fixation ● Phytoremediation ○ use plants to extract Cd or reduce contamination

Soil Remediation - Comparison Advantages Disadvantages Excavation -Contaminants completely removed -Relatively rapid -Contaminants are just relocated and must still be monitored -High risk of spreading contaminated soil and dust (occup. hazard) -High cost Stabilization -Relatively rapid -Does not disrupt environment -Takes same amount of time as excavation -More costly than phytoremediation -Low cost -Wide public acceptance -Can cost less than 25% of cost of excavation or in situ fixation -Takes longer than other methods Phytoremediation

Soil Remediation - Costs and Time Required

Phytoremediation There are different types: ● Phytostabilization ○ ○ Experimental phytoremediation crops in Canada (Environment Canada) Plants are used to reduce erosion Grass and tree buffers can reduce sediment loss from contaminated sites 18 -25% (EPA) If the entire area is revegetated, sediment loss can be cut by 70% (EPA) Note: must use plants that can tolerate high levels of Cadmium ● Phytoextraction ○ ○ Some species can take up heavy metals and concentrate them in their tissue Plants can then be harvested and disposed of safely Soil amendments can be added to increase ability of plants to take up metals Common plants used: India mustard, alfalfa, cabbage, tall fescue, juniper, poplar trees ● Rhizofiltration ○ Heavy metals are removed from water by plant roots

Other Soil Remediation Methods ● Soil washing ○ Liquid + mechanical process used to scrub soil ■ Often water combined with chemical additives ● ○ ○ Study: sequential soil washing using Na 2 EDTA, oxalic and phosphoric acid resulted in removal of 41. 9% arsenic and 89. 6% cadmium from the soil (Wei et al. , 2016) Contaminants bind to silt and clay Contaminated fine soil (silt/clay) separated from coarse soil (sand/gravel) Smaller volume of soil containing the majority of fine clay/silt particles can then be treated by other methods (incineration, bioremediation) or disposed of Advantages: ■ hazardous wastes can be excavated and treated on site ■ can remove wide variety of chemical contaminants from soils: metals, gasoline, fuel oils, pesticides ■ cost-effective

Other Soil Remediation Methods ● Soil washing with biopolymers ○ ○ ○ Tunable biopolymers, biosurfactants, metal chelating biopolymers Produced by bacteria Advantages: ■ environmentally friendly ■ biopolymers can be reused https: //archive. epa. gov/ncer/publications/web/pdf/wilfred_chen_aug_20. pdf

Air ● ● Cadmium concentrations in ambient air are generally low Air cadmium contributes only to less than a few percent of the total absorbed dose of cadmium in the body Cadmium-polluted air may occur in the vicinity of some metal industries Mining activities and the application of cadmium-containing fertilizers and sewage sludge on farm land may lead to the contamination of soils and increased cadmium uptake by crops and vegetables grown for human consumption.

Water ● ● Main sources : corrosion of galvanized pipes, erosion of natural deposits, runoff from waste batteries and paints Health effects ○ Short term: nausea, vomiting, muscle cramping, liver injury, shock, convulsions, renal failure ○ Long term: kidney, liver, bone and blood damage ● Other dangers: ○ Water ending up in soils ○ Getting in to the food chain ■ Ex. Meats, vegetables, etc. <- Cadmium pollution in S. China River

Cadmium in Bangkok ● ● 14 Nov, 2018 Two mining companies in Thailand lose around 16 million baht (~$500, 000 USD) because of cadmium leaks ~884 villagers were found with high levels of cadmium in blood Companies already had to pay 50 million baht (1. 5 mil USD) to Thai government as clean up fees

Removal Processes for Water Residential ● ● Strong Acid Cation Resin Weak Acid Cation Resin Reverse Osmosis Distillation Municipal ● Strong Acid Cation Resin ● Precipitation/filtration/flocculation ● Lime softening

Sources https: //safewater. zendesk. com/hc/en-us/articles/211403358 -5 -How-does-cadmium-get-into-my-drinking-waterhttps: //www. atsdr. cdc. gov/csem. asp? csem=6&po=5 https: //www. sciencedirect. com/science/article/pii/S 0041008 X 09001690 https: //cfpub. epa. gov/ncer_abstracts/index. cfm/fuseaction/display. files/file. ID/14295 https: //nepis. epa. gov/Exe/Zy. PURL. cgi? Dockey=10002 SYY. tx https: //www. ncbi. nlm. nih. gov/pubmed/15224748 https: //www. bangkokpost. com/news/general/1575334/cadmium-sickened-villagers-awarded-b 16 m-compensation Wei, M. , Chen, J. , & Wang, X. (2016). Removal of arsenic and cadmium with sequential soil washing techniques using Na 2 EDTA, oxalic and phosphoric acid: Optimization conditions, removal effectiveness and ecological risks. Chemosphere, 156 , 252 -261. doi: 10. 1016/j. chemosphere. 2016. 04. 106