Preliminary Studies of the Development of Heavy Metal Ions Pre-concentration Technique Using Sodium Sulfide and Chitosan

Tee, Li Ze (2017) Preliminary Studies of the Development of Heavy Metal Ions Pre-concentration Technique Using Sodium Sulfide and Chitosan. Final Year Project (Bachelor), Tunku Abdul Rahman University College.

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Abstract

This study aims to develop a better heavy metals pre-concentration technique with high percent recovery by using sulfide precipitation and chitosan. Sulfide precipitation was carried out by introducing sodium sulfide solution into the heavy metals sample solution. After that, the insoluble sulfide formed was filtered by using syringe filter and then elute out by using 4 mL of 40 % HNO3 as the eluent. The percent recovery for copper was always found higher than that of the nickel. It was believed that the nickel sulfide was still trapped in the syringe filter after the elution with HNO3. This caused the nickel detected by AAS to be lower than that of copper. After that, another new material, chitosan was being used as the pre-concentration material to pre-concentrate the heavy metal. However, the preconcentration could not be done as chitosan has low acid stability and tends to swell up, increase in size and form gel when acid was introduced at the acid elution stage. Therefore, tests were conducted to determine the optimum amount of chitosan and optimum of acid concentration that should be used in the elution. Besides, attempts were also made in order to determine whether the powder form chitosan was viable to be made and still possess the adsorption function or not. It was found that the optimum amount of chitosan was 0.5 g and the optimum acid concentration for 0.5 g chitosan was 1 % and 2 % HNO3. Other than that, the chitosan powder which was produced from the previous nickel adsorption test was found to have adsorption function even though the percent removal of heavy metals was not satisfactory.