Catalytic reduction of p-nitrophenol and methylene blue by microbiologically synthesized silver nanoparticles.

Catalytic Reduction of p-nitrophenol and Methylene blue by Microbiologically Synthesized Silver Nanoparticles was studied in the present investigation. Catalytic reduction of 4-Nitophenol/p-nitrophenol (PNP) and methylene blue (MB) was assessed using both intra and extracellular silver nanoparticles (AgNP) with and without immobilization. Both intracellular and extracellular AgNP were synthesized from actinomycetes. Antimicrobial activity of AgNP was also assessed and it was found that, intracellular AgNP have significant antibacterial activity against E. coli, S. typhi and B. subtilis. Synthesized biogenic silver nanoparticles were characterized by UV-visible spectrophotometry, FTIR, XRD, and TEM-EDS. It was found that, extracellular AgNP are efficient as compared to intracellular AgNP in terms of PNP reduction.

Comparative bioleaching of metals from pulverized and non-pulverized PCBs of cell phone charger: advantages of non-pulverized PCBs.

Sample inhomogeneity is a severe issue in printed circuit boards especially when we are comparing the bioleaching efficiency. To avoid the ambiguous results obtained due to inhomogeneity in PCBs, 12 similar cell phone chargers (of renowned company) having same make and batch number were collected from scrap market. PCBs obtained from them were used in present studies. Out of these 12, three PCBs were used separately for chemical analysis of PCBs with prior acid digestion in aqua regia. It was found that, 10.8, 68.0, and 710.9 mg/l of Zn, Pb, and Cu were present in it, respectively. Six PCBs were used for bioleaching experiment with two variations, pulverized and non-pulverized. Though the pulverized sample have shown better leaching than non-pulverized one, former has some disadvantages if overall recycling of e-waste (metallic and nonmetallic fraction) is to be addressed. At the end of leaching experiments, copper was recovered using a simple setup of electrodeposition and 92.85% recovery was attained. The acidophiles involved in bioleaching were identified by culture dependent and culture independent techniques such as DGGE and species specific primers in PCR.