Development of a PANI/Fe(NO3)2 nanomaterial for reactive orange 16 (RO16) dye removal.

Polyaniline-iron(II) nitrate was prepared by the polymerization of aniline hydrochloride with Fe(NO3)2. The as-prepared materials were characterized for surface area and pore volume and were used to remove the reactive orange 16 (RO16) dye from an aqueous solution. Batch studies were conducted as a function of pH (2-12), adsorbent amount (10-100 mg), initial RO16 concentration (100-300 mg L-1), contact time (10-240 min), and temperature (303-323 K). RO16 was removed at high speed, and equilibrium was achieved in 80 min. Langmuir (six linear forms, i.e., L-I-VI) and other isotherm models were explored for their applicability. With the maximum adsorption capacity of 508.7267 mg g-1 and a pH of 4 at 313 K, the adsorption isotherm could be adequately characterised using the Langmuir (L-V) model. The kinetics of the adsorption process were investigated by fitting experimental data to pseudo-second order (PSO) (type-I-VI) and other kinetic models, with the findings indicating that the adsorption closely matched the PSO-I model. For isotherm models, twelve linear error functions were investigated. The absorption process was spontaneous, endothermic, and feasible according to the thermodynamics study (ΔG° = -8.8888 kJ mol-1, ΔH° = 3.1940 kJ mol-1, and ΔS° = 39.8749 J mol-1 K-1). The phototoxicity studies revealed that the untreated dye was highly toxic compared to the treated dye. It was also shown that the material could be recycled substantially, with an RO16 value of 82.8%. The findings also indicated that the PANI/Fe(NO3)2 material was sufficient for RO16 dye adsorption in both model and real water samples.

Metal solubilization from powdered printed circuit boards by microbial consortium from bauxite and pyrite ores.

With the current rapid developments in technology, there is an increasing accumulation of outdated electronic equipment. The primary reason for this increase is the low rate of recycling due to the complex nature of such waste. Bioleaching offers a promising solution for this problem. Study was conducted on the solubilization of heavy metals from electronic waste (e-waste). For this purpose, a microbial consortium from bauxite and pyrite ore samples was obtained using a simple "top down" approach. Essentially, printed circuit boards (PCB) were obtained and used as representative samples of e-waste. Various concentrations (1-5%) of PCB powder were subjected to bioleaching, and the effects on metal solubilization, changes in pH and concentration of ferrous iron produced were assessed. It was observed that a maximum of 96.93% Cu and 93.33% Zn was solubilized by microbial consortium from 10 g/l of PCB powder, whereas only 10.26% Ni was solubilized from 30 g/l of PCB powder. For lead, only 0.58% solubilization was achieved from 20 g/l of PCB powder. An analysis of the precipitate formed during bioleaching using scanning electron microscopy with energy dispersive x-ray analysis revealed the presence of Tin (59.96%), Cu (23.97%), Pb (9.30%) and Fe (5.92%).