Microwave-assisted desulphurization of coal in alkaline medium and conditions optimization by response surface methodology

The coal is an imperative source of energy, which on combustion, it emits sulphur dioxide, which cause air pollution. In the present study, microwave mediated desulphurization of coal was investigated and input variables were optimized by response surface methodology (RSM). The proximate analysis and ultimate analysis report indicate the sample belongs to subbituminous having sulphur (6.96%), volatile matter (34.5%) and calorific value (5099 kcal/kg). Under microwave irradiation, up to 68% of sulphur was leached in alkaline medium. The particle size of coal, concentration of potassium hydroxide (KOH), microwave exposure time and power of microwave radiation were systematically optimized for maximum desulphurization of the coal. Under optimum conditions of the process variables, 63.06% desulphurization of coal was achieved. The optimum levels of process variables are as, particle size 500 µm, irradiation time 8.54 min, radiation power 720 W and concentration of KOH 15% (w/v). Findings revealed that the microwave-assisted desulphurization under alkaline condition furnished promising efficiency, which can be employed for the desulphurization of coal.

Preparation and comparative evaluation of PVC/PbO and PVC/PbO/graphite based conductive nanocomposites

Two series, A and B, of PVC based nanocomposite polymer membranes (nCPMs) were prepared using PbO only and PbO/graphite mixture as a filler by solution casting method. Seven samples with varying compositions (5–35%) of filler particles were prepared for each series and were compared by thickness measurements, porosity, water uptake, swelling degree, ionic conductivity, ion exchange capacity (IEC), membrane potential and transport number. The maximum values for these characteristics were observed as 0.402 mm, 0.77, 141.3%, 0.11, 0.0033 Scm−1, 8.6 milli-eq.g−1, 0.19 V and 0.01391 for series-A composites whereas that of 0.367 mm, 0.83, 63.4%, 0.019, 0.00981 Scm−1, 5.21 milli-eq.g−1, 0.13 V and 0.0108 for series-B nCPMs respectively. The SEM images of membranes showed greater voids produced in the series-B compared to series-A composites. The maximum Ionic conductivity, IEC, membrane potential and transport number were observed for membrane with 25% PbO/graphite, 20% PbO and 35% PbO particles respectively.