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A novel approach was introduced to remove metal (Ag+) ions from aqueous solution and subsequently restate the metal-loaded materials for a number of environmentally friendly applications. A versatile adsorbent, polypyrrole with mercapto-functionalized chelating groups (PPy/MAA), successfully adsorbed Ag+ ions through subsequent reduction to silver nanoparticles (Ag0 NPs) into the composite matrix. The as-prepared composite (PPy/MAA) and Ag-adsorbed PPy/MAA (PPy/MAA/Ag0) were fully characterized by FE-SEM, EDS, HR-(S)­TEM, XRD, FTIR, BET, XPS, and zeta potential measurements. Batch adsorption results showed that the adsorption process can be explained well by a pseudo-second-order model. The maximum adsorption capacity calculated using a Langmuir isotherm model was 714.28 mg/g at 25 °C. XRD, XPS, and HR-TEM analyses confirmed the presence of metallic silver nanoparticles on the surface of the composite matrix after the in situ reduction of Ag+ to Ag0. Among the applications tested, the metal-loaded waste (PPy/MAA/Ag0) was found to have antimicrobial activity, as it inhibited the growth of Escherichia coli, while pure adsorbent without silver showed no killing effect toward E. coli. PPy/MAA/Ag0 also played an important role in the catalytic reduction of 4-nitrophenol and also exhibited good sensitivity to NO2 in gas-sensing applications. Therefore, the developed PPy/MAA composite achieved 2-fold environmental benefits, not only remediating Ag+ from polluted waterways but also opening a new window for subsequently acting as an agent for antibacterial ability, catalytic activity, and gas-sensing efficiencies.

Problems related with highly toxic mercury emissions from industrial effluents are one of the great concerns in the world of environmental science and technology. The primary aim of this present work is the remediation of hazardous pollutant Hg (II) from aqueous medium via a thiol-functionalized (mercaptoacetic acid) conducting polypyrrole (PPy/MAA) composite. The synthesized composite exhibited high Hg­(II) adsorption capacity as the incorporated mercapto functionality plays a vital role for the strong binding affinity toward Hg­(II) ions. To understand the adsorption properties of the developed polymer composite, a series of batch adsorption experiments were performed by altering the adsorption parameters. A maximum adsorption capacity (q max) of 1736.8 mg/g at 25 °C was obtained using the Langmuir isotherm. The adsorption data showed better fitting to the pseudo-second-order rate equation for Hg­(II) adsorption. A plausible adsorption mechanism is suggested on the basis of XPS results of major elements present in the adsorbent. To apply to catalytic reactions, the use of waste-derived mercury-adsorbed material (termed as PPy-MAA/Hg (II)) is also addressed here for further application of organic transformation. Here, we described the catalytic reaction with phenylacetylene in the presence of 5 mol % PPy-MAA/Hg (II) catalyst at 90 °C for 6 h. This method provides a straightforward formation of acetophenone in 55% yield. Thus, PPy/MAA not only effectively eliminates toxic Hg­(II) ions from water but also is successfully applied for the catalytic organic transformation after adsorption.

The palladium-catalyzed efficient cross-couplings of mono-, di-and tetra-bromo-1,4-quinones with triarylbismuth reagents were developed, involving threefold arylation. This first time study which is demonstrated with a wide variety of substrates possesses high synthetic utility and furnished a plethora of arylated 1,4-quinones in a one-pot operation.

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Nano-sized magnetic Fe/polyaniline (Fe/PANI) nanofibers were used as an effective material for sonocatalytic degradation of organic anionic Congo red (CR) dye. Fe/PANI was synthesized via reductive deposition of nano-Fe onto the PANI nanofibers at room temperature. Prepared catalyst was characterized using HR-TEM, FE-SEM, XRD, FTIR instruments. The efficacy of catalyst in removing CR was assessed colorimetrically using UV-visible spectroscopy under different experimental conditions such as % of Fe loading into the composite material, solution pH, initial concentration of dye, catalyst dosage, temperature and ultrasonic power. The optimum conditions for sonocatalytic degradation of CR were obtained at catalyst concentrations=500mg.L, concentration of CR=200ppm, solution pH=neutral (7.0), temperature=30°C, % of Fe loading=30% and 500W ultrasonic power. The experimental results showed that ultrasonic process could remove 98% of Congo red within 30min with higher Q value (Q=446.4 at 25°C). The rate of degradation of CR dye was much faster in this ultrasonic technique rather than conventional adsorption process. The degradation efficiency declined with the addition of common inorganic salts (NaCl, NaCO, NaSO and NaPO). The rate of degradation suppressed more with increasing salt concentration. Kinetic and isotherm studies indicated that the degradation of CR provides pseudo-second order rate kinetic and Langmuir isotherm model compared to all other models tested. The excellent high degradation capacity of Fe/PANI under ultrasonic irradiation can be explained on the basis of the formation of active hydroxyl radicals (OH) and subsequently a series of free radical reactions.

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