Waste PCB is a complicated and valuable electronic waste. E-waste production is increasing at a high alarming rate in industries. Now, it is more important to recycle and reuse it. WPCB contains various noble metals such as copper, nickel, aluminum, lead, zinc, etc. If these wastes are dumped in lands, it’s hazardous to land. So, it is important to recycle it. There are various processes to recycle it, but not all the process are environmental friendly. In this study, we discussed about the two process namely chemical leaching and bioleaching. Chemical leaching involves the use of hydrochloric acid, malic acid and citric acid whereas the bioleaching involvbes the production of organic acid using Aspergillus niger. The main aim is to extract the valuable metals such as copper and nickel from the waste PCB. The effect of time and concentration on leaching were investigated. The characterization of the E-waste was studied and the leaching recovery percentage was found. This study also shows that comparative study between chemical leaching and bioleaching.

Ferritins, the cellular iron repositories, are self-assembled, hollow spherical nanocage proteins composed of 24 subunits. The self-assembly process in ferritin generates the electrostatic gradient to rapidly sequester Fe(II) ions, thereby minimizing its toxicity (Fenton reaction). Although the factors that drive self-assembly and control its kinetics are little investigated, its inherent reversibility has been utilized for cellular imaging and targeted drug delivery. The current work tracks the kinetics of ferritin self-assembly by laser light scattering and investigates the factors that influence the process. The formation of partially structured subunit-monomers/dimers, at pH ≤ 1.5, serves as the starting material for the self-assembly, which upon increasing the pH exhibits biphasic behavior (a rapid assembly process coupled with subunit folding followed by a slower reassembly/reorganization process) and completes within 10 min. The ferritin self-assembly accelerated with subunit concentration and ionic strength (t1/2 decreases in both the cases) but slowed down with the pH of the medium from 5.5 to 7.5 (t1/2 increases). These findings would help to regulate the ferritin self-assembly to enhance the loading/unloading of drugs/nanomaterials for exploiting it as a nanocarrier and nanoreactor.

In the present study, we have investigated the effects of surfactant addition on the structure and dynamics of gellan gum hydrogels. A strong interaction is seen between gellan gum and oppositely charged cationic surfactant, hexadecyltrimethylammonium bromide (CTAB) whereas rather weak or minimal interactions are observed when either anionic surfactant, sodium dodecylsulfate (SDS), or nonionic surfactant, Triton X-100 is added to the system. The dynamics of the hydrogels was studied, using dynamic light scattering measurements and the heterodyne method was used for data evaluation. The correlation function of parent hydrogel was fitted with a stretched exponential function, while a single plus stretched exponential function was employed to study the dynamics of hydrogel with surfactants and the corresponding relaxation times were appropriately analyzed. An interesting crossover from stretched to compressed exponential was seen when CTAB was added beyond critical micellar concentration to the system, which was not evidenced for the other two surfactants. Ensemble averaged intensity was also analyzed and the general picture that emerges is that the oppositely charged surfactant has the strongest ability to form large associations as oppose to nonionic and like-charged surfactants. The rheological measurements were carried out to determine the elastic response of the gels over a wide range of frequencies. It was seen that the elastic modulus was dependent on both the surfactant concentration and type. Cationic surfactant increased the elastic modulus markedly as opposed to the nonionic and anionic surfactants. These results may have implications for the use of polymer surfactant systems as potential products.

The dynamical behavior of charged poly-acrylic acid solutions is investigated in the presence and absence of electrolyte using dynamic light scattering measurements. An interesting non-ergodic to ergodic transition is observed for polyelectrolyte solution with addition of excess salt. Our study shows two modes of diffusive processes that are greatly influenced by inter-molecular interactions occurring inside the charged polymer systems, which in turn affect the correlation length and thereby showing changes in structural behavior of the polyelectrolyte solutions.

The dynamics of Acrylamide-co-Sodium acrylate hydrogels with the variation in sodium acrylate (SA) content was investigated by partial heterodyne approach using dynamic light scattering. It was seen that with the addition of hydrophilic sodium acrylate into the polyacrylamide matrix, the extent of frozen in structure and fluctuations is reduced. Also the spatial inhomogeneities in the network was greatly suppressedas a result of rise in SA concentration. Cooperative diffusion coefficient decreased which may be attributed as the decrease in crosslinking efficiency of crosslinker with the addition of sodium acrylate.

The effect of varying initial monomer concentration on the microstructure and rheological properties of poly (sodium acrylate) hydrogel was investigated. It was seen that as polymer concentration increased, mechanical strength and elasticity of the network also increased till 25 wt% beyond which it saturates. In the case of loss modulus a similar increase is observed with increase in polymer concentration upto 25 wt%, past which there is a minor drop for 30 wt% gel indicating marginal drop in gel strength. The frequency sweep results showed predominant elastic response typical for a strong gel. A solid-like mechanical response was also confirmed by analyzing complex viscosity of respective hydrogels.

The dynamics of polyacrylamide hydrogels with and without entrapped anionic polyelectrolyte chains have been investigated using dynamic light scattering measurements. A non - ergodic treatment of the data suggests a striking alteration in system dynamics for gels embedded with polyelectrolytes when compared with parent gel. The gels exhibited an increasingly non - ergodic behaviour with maximum frozen in structure for gels with highest concentration of polyelectrolyte chains indicating stiffening of network junction. The analysis by short time expansion of intermediate scattering function suggests there is a decrease in mesh size with increase in polyelectrolyte concentration.

Probe diffusion of fluorescently labeled Dextran 40 inside polyelectrolyte solution of polyacrylic acid (PAA) was investigated using Fluorescence Recovery After Photobleaching technique. The crowding and interaction effects on probe diffusion were controlled by tuning background polymer and added external electrolyte concentration. For all the salt concentration, an overall decrease in diffusion coefficient is observed with rise in polymer concentration. The diffusion coefficient decreases with decrease in salt concentration whereas the solution viscosity increases, indicating a competition between viscous drag and electrostatic interaction. A large positive deviation from the ideal Stokes-Einstein relation is observed for high polymer and low salt concentration, which reduces markedly with addition of salt confirming polyelectrolyte effects, plays a major role in deciding the probe diffusion.

We have investigated the effect of ionic and non – ionic surfactants on the structure and rheological properties of polyacrylamide hydrogels. With addition of ionic and non-ionic surfactants, just below and above their critical micellar concentration (CMC), there is a significant decrease in hydrogels mechanical strength as compared to the parent hydrogels alone. In oscillatory measurements, no frequency dependence is observed in the case of polyacrylamide hydrogels. However with the addition of surfactants, just below and above CMC, noticeable frequency dependence is observed.

Rheological measurements on gellan gum hydrogels were carried out to investigate the effect of an anionic surfactant, sodium dodecyl sulfate (SDS) on hydrogel structure. The gel strength was found to be strongly correlated to surfactant concentration. Below the Critical Micellar Concentration (CMC), we observed an increase in gel strength with rise in surfactant concentration and a reverse trend is observed for surfactant concentration above CMC. The gel network structure is found to be highly elastic below CMC, while an aggregated network is observed at higher concentration of surfactant. With the addition of surfactant, sol to gel transition temperature of Gellan Gum is shifted to higher temperature, suggesting addition of surfactant promotesas well as stabilizes the helix formation.

Hydroxypropyl Cellulose (HPC) microgels were prepared by emulsion polymerization method. The volume phase transition temperature (VPTT) and swelling properties were investigated using Dynamic Light Scattering (DLS). The VPTT for the HPC microgels was found to be similar to 44 degrees C. Microgel particles swelled similar to'3' times of their original size on decreasing temperature from 50 degrees C to 25 degrees C. In addition we have also studied the effect of salts, sodium nitrate and sodium bromide in the Hofmeister series on deswelling and colloidal stability of HPC microgels using DLS and turbidity measurements respectively. Microgel particles swelled in presence of NaNO3 when its concentration was increased from 10(-4) to 0.5 M and deswelled beyond it. As oppose to this, swelling of microgels in presence of NaBr was seen only upto 10(-3) and beyond which deswelling of microgels was observed. The results obtained are consistent with Hofmeister series of anions. Turbidity results showed that the colloidal stability of HPC microgel dispersion was dependent on ionic strength and type of added salt. For both salts, stability of microgels was found to decrease with rise in salt concentration.