Emerging Science Journal
|
Vol. 3, No. 2
Page | 104
2-7- Metal Adsorption Capacity of Prepared Lignin Based Resin
In order to investigate the metal adsorption capacity, 2 grams of resins were mixed with 10 ml solution of cadmium
ion (Cd
2+
). The mixture was incubated for 24 hour at room temperature with constant stirring. Mixture was filtered after
24 hours. Amount of metal adsorption was determined by using Atomic Absorption Spectrometer. Adsorption capacity
at equilibrium state was determined according to the Langmuir equation [15].
𝑞𝑒 =
𝐶𝑜 − 𝐶𝑒
𝐷
(2)
Where,
𝐶𝑜
- initial metal concentration in solution;
𝐶𝑒
- equilibrium metal concentration in solution;
𝐷
- Sample dose.
A summary of research methodology displayed in Figure 1.
Figure 1.
Flow chart for the research methodology
3- Results and Discussion
3-1- Uncured and Cured Phenolic Resin
At the end of the reaction at 90°C, a solutions having high viscosity was obtained for all resin. Alkaline medium with
molar excess formaldehyde used to form resols resins. This condensation Reaction leads
to the three dimensional
network product having high molecular weight. It causes the resin to gel which is attributed to the high viscosity of the
solution. The free hydroxyl groups of the phenol in the resin are mildly acidic and dissociate partially in water. But in
the presence of the base (NaOH) they form alkoxide salts (of Sodium). These salts are ionic and completely dissociate
in water due to the strong ion-dipole bonding leads water soluble resin. However when the medium is acidified with
HCl the free hydroxyl
groups are regenerated, restrict the resin soluble in water. Eventually
the resin solidifies and
separates out of the solution as a precipitate.
The synthesised resin showed a variation in colour and strength. Virgin phenol formaldehyde resols (PFR), that had
no
additives, displayed a cream colouration. And pure phenol formaldehyde novolac resin (PFN)
displayed a pink
colouration. Resoles were exhibit more rigidity than Novolac resin.
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