Abstract:
Natural rubber is extracted from the bark of the trunk of Hevea brasiliensis tree
by a process called tapping. Field latex is centrifuged to concéntrate its DRC (Dry Rubber
Content) depending on the purpose. This process results skim latex as a byproduct which has 3-7% DRC. Incomplete coagulation of skim latex results environmental problems when it is discharged to the environment and henee expence high value to treat effluent. The current skim processing involves the recovery of 4-5% of rubber content by cheap grade sulphuric acid coagulation. By using proper acid dosage, maximum rubber yield can be recovered reducing effluent problems.
In the assessment, skim is treated with sulphuric and formic acids and then with
different concentrations, until maximum yield of rubber is obtained. Also papain, protein
digesting enzyme, is used as altemative coagulant after neutralizing skim with sulphuric acid.
The coagulation of latex by the addition of acids is a result of the precipitation of the
protective layer of proteins around the rubber globules in the latex by lowering of pH.
As a result of series of trials, 25% formic acid and 98% sulphuric acid recover
higher yield than others. To coagulate 100 L of skim, only lkg and 2kg of sulphuric acid and
formic acid are enough respectively. 98% sulphuric acid yields recovery of 98% rubber while formic acid yields 97%. In neutral State of skim, very low quantity of papain is enough to coagulate than in normal State due to its enzymatic activity. Extracted protein levels of dried producis were varied from the expected results. However coagulation with alum separate rubber, but can not get separated as it come as a suspension.
The DRC value after 14 hours was further reduced when drying duration was
lengthen up to 18 hours. Then the latter was used during the result calculation. The recovered yield of rubber becomes increasing with increasing the concentration of sulphuric acid and vice versa, but not other coagulating agents.
