Lead is widespread throughout our environment for extensive industrial applications, modern agricultural practices, municipal landfills, and sewage disposal. In order to restrict the emanation of lead-containing waste from industries eco-friendly cost-effective bioremediation process has to be conducted with the chemically treated lead-containing industrial waste. The current study deals with comprehensive experiments on bioremediation of lead under different operating conditions using the isolated lead-resistant bacterium Acinetobacter sp. (isolated in-house from a native source). Two substrates, viz., glucose and lead, have been utilized to understand the cell growth kinetics of the bacteria under lead microenvironment. An attempt has also been made to quantify the cell growth kinetics in the form of mathematical model equations with a proper explanation of the procedure to find out intrinsic kinetic parameters from experimental data. Rigorous modeling and simulation exercises reveal that a multiplicative noncompetitive relationship is present between glucose and lead with respect to bacterial cell growth. Bioremediation of lead using the isolated strain has also been carried out in a continuous mode packed-bed bioreactor with an intention to extend the process in large-scale mode. Initially, the isolated biomass has been immobilized on an inert matrix using the attached growth technique. The conjugate biocatalyst so formed has been used as a packing in a specially designed packed-bed reactor. From the comprehensive experimental runs, it was observed that at superficial velocity 1.4 m/h, lead was eliminated up to 80.4% from the wastewater stream having 0.04 g/L initial concentration of lead.

The current investigation presents an innovative approach to address the challenge of removing heavy metal lead from industrial waste through advanced biological remediation techniques. By amalgamating theoretical insights with empirically acquired data, this research endeavours to develop efficient bioreactor strategies suitable for large-scale applications. Initially, bacteria naturally endowed with lead resistance has been isolated from a native source. Extensive microbiological assessments, including a 16S rDNA study, verified the identity of the lead-resistant bacterial cells as Bacillus infantis 4352-1T. In order to evaluate the efficacy of Bacillus infantis 4352-1T for lead removal an attempt has been made to study the growth dynamics of Bacillus infantis 4352-1T cells in batch mode, using lead amended selective media. It has been observed that Monod's equation effectively defined the cell growth behaviour within the lead concentration range of 0.05-0.25 kg lead/m(3). Notably, the experiment was also facilitated the derivation of essential intrinsic kinetic parameters, such as the maximum specific cell growth rate (0.0237 h(-1)) and substrate saturation constant (0.018 kg/m(3)). Beyond lead concentrations of 0.25 kg lead/m(3), up to 0.43 kg lead/m(3), it has also been observed the pronounced influence of substrate inhibition which is quantitatively elucidated by the Haldane equation.

Synthesizing hydrosulfido Cu thiolate complexes is quite challenging. In this report, two new and rare hydrosulfido Cu thiolate complexes, [Et4N]2[(mnt)Cu-SH] (2, mnt = maleonitrile dithiolene = S2C2(CN)2) and [Et4N]3[(mnt)Cu-(μ-SH)-Cu(mnt)] (3), have been synthesized. Coordination sites and O2 activation by complex 2 resemble the formylglycine generating enzyme (FGE), an enzyme recently crystallographically characterized with sulfur-only coordination around Cu (three thiolate ligands). The function of this enzyme (and complex 2) is surprising because vulnerable thiolates should not be well suited for O2 activation rationally. Indeed, activation of oxygen by such an all-sulfur-coordinated Cu complex 2 is lacking in the literature. Aerial O2 (ambient O2 from the air) activation by complex 2 could proceed through a superoxide radical intermediate and a sulfur radical intermediate detected by resonance Raman (rR) spectroscopy and electron paramagnetic resonance (EPR) spectroscopy, respectively. The chemistry of 2 has been examined by its reactivity, crystal structure, and spectroscopic and cyclic voltammetric analyses. In addition, the results have been complemented with density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations.

A mathematical model was developed from first principle to predict the concentration distribution in the axial direction in a packed bed biofilm reactor used for the removal of lead from wastewater by bioremediation. The biocatalyst was prepared by immobilizing Acinetobacter sp . 158 (isolated in-house from a native source) on a sintered sticky Earthen sphere using an attached growth technique. To evaluate the intrinsic kineticparameters necessary for the simulation, batch mode studies of the same system were carried out, and the cell growth dynamics were established. It was observed that within the concentration of lead from 0.01 kg m −3 to 0.04 kg m −3 the system followed the Monods substrate uninhibited model equation. The first order differential equation obtained through thesteady-state mass balance in the axial direction of the packed bed contained no adjustable parameters, and the equation was solved analytically. Within the lead concentration range 0.01 kg m −3 −0.04 kg m −3 and flow velocity 1.43 m h −1 −5.73 m h −1 experimental data shows best alignment with the simulated values. The close fit of such experimental data with the simulated values indeed clearly indicates the validity of the proposed deterministic model equation.

Current research on catalysts for proton exchange membrane fuel cells (PEMFC) is based on obtaining higher catalytic activity than platinum particle catalysts on porous carbon. In search of a more sustainable catalyst other than platinum for the catalytic conversion of water to hydrogen gas, a series of nanoparticles of transition metals viz., Rh, Co, Fe, Pt and their composites with functionalized graphene such as RhNPs@f-graphene, CoNPs@f-graphene, PtNPs@f-graphene were synthesized and characterized by SEM and TEM techniques. The SEM analysis indicates that the texture of RhNPs@f-graphene resemble the dispersion of water droplets on lotus leaf. TEM analysis indicates that RhNPs of <10 nm diameter are dispersed on the surface of f-graphene. The air-stable NPs and nanocomposites were used as electrocatalyts for conversion of acidic water to hydrogen gas. The composite RhNPs@f-graphene catalyses hydrogen gas evolution from water containing p-toluene sulphonic acid (p-TsOH) at an onset reduction potential, Ep, −0.117 V which is less than that of PtNPs@f-graphene (Ep, −0.380 V) under identical experimental conditions whereas the onset potential of CoNPs@f-graphene was at Ep, −0.97 V and the FeNPs@f-graphene displayed onset potential at Ep, −1.58 V. The pure rhodium nanoparticles, RhNPs also electrocatalyse at Ep, −0.186 V compared with that of PtNPs at Ep, −0.36 V and that of CoNPs at Ep, −0.98 V. The electrocatalytic experiments also indicate that the RhNPs and RhNPs@f-graphene are stable, durable and they can be recycled in several catalytic experiments after washing with water and drying. The results indicate that RhNPs and RhNPs@f-graphene are better nanoelectrocatalysts than PtNPs and the reduction potentials were much higher in other transition metal nanoparticles. The mechanism could involve a hydridic species, Rh-H− followed by interaction with protons to form hydrogen gas.

The present investigation deals with an in-depth study on optimization of lead removal capacity of lead-resistant bacterium Acinetobacter sp. 158 as a response variable with limiting carbon source, pH, and rotational speed as non-interacting-type independent variables. The statistical optimization technique response surface methodology has been used for this purpose. The optimum parameters of the independent variables have been identified through 3D plots. A set of deterministic model equations have been developed through rigorous modeling and simulation to predict the cell growth dynamics of the lead-resistant bacterium Acinetobacter sp. 158. A set of programmed experiments have been conducted using the optimized value of the independent variables obtained through RSM to validate the proposed model equations.

A dithiolate/hydride bridged Fe-Ni complex, [(CN)(CO)2FeII(μ-pdt)(μ-H)NiII(CN)(PCy3)]- (2, pdt = propane-1,3-dithiolate) has been synthesized by the reaction of [(CN)2(CO)2FeII(pdt)]2- with [NiII(Cl)(H)(PCy3)2] as a synthetic analogue of the Ni-R state of the active site of the [Ni-Fe] hydrogenase. X-ray crystallography of this model complex suggests that the hydride unsymmetrically binds to Ni and Fe similar to natural [Ni-Fe] hydrogenases.

With large surface area and versatile electronic behaviour, the composites of Fe₄S₄(SRS)₄ nanoclusters and functionalized carbon nanotubes (f-CNTs), are expected to catalyze the conversion of protons to hydrogen gas at lower electro-potentials with higher output than a platinum electrode. In search of a non-noble metal based catalytic material, we report for the first time, the isolation of unimolecular iron-sulfur cubane cluster, [Fe₄(μ-S)₄(mnt)₄], (1) (mnt = maleonitriledithiolate) as nanocubes (63×85×120 nm) in MeCN-EtOH (MeCN is acetonitrile, while EtOH is ethanol) solvents and bimolecular [NBu₄]₄[Fe₄(μ-S)₄(mnt)₄] as nanocuboctahedra (120×121×125 nm) in pure EtOH. The cubic shape of the nanocrystal reminds its geometrical relationship with a molecular cube and one of sides of the nanocube and nanocuboctahedron matches at 120 nm. The nanocubes of Fe₄S₄(SRS)₄ have been immobilized on f-CNTs and characterized by SEM and TEM methods which indicate that clusters of Fe₄S₄ of diameter (8-9 nm) interact with surfaces, sidewalls and tip of the f-CNTs. A ferrocene type of interaction could not be observed with f-CNTs, because nanoparticles are not found in CNT-inner cavity. The interaction could be either adsorption or hydrogen bonding interactions between -COOH/-OH groups of f-CNTs and N≡C terminals of iron-sulphur nanoclusters leading to immobilization of an iron-sulfur nanocluster on a single CNT molecule or the iron-sulfur nanoclusters can be entrapped between two CNT molecules.

The dissymmetric binuclear complex1acts as a precursor of the molybdoenzyme models of the dimethylsulfoxide reductase (DMSOR) class.

The Mo(iv) bis (dithiolate) complex showed diverse reactions with Me3SiCN in the presence and absence of a coligand and under protic and aprotic media.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

•Isolation and purification of lead resistant bacterium is done.•Chemotaxonomy of the isolated strain has been carried out to establish the genus and species of the strain.•FESEM, XRD, EDX, SDSPAGE experiments have been conducted to characterize the isolated strain.•Modeling of cell growth dynamics based on Monods substrate uninhibited unstructured equation is presented.•Validation of the model equation is done using extensive experimental data.

Three new complexes, [Mo(IV)O(mnt)(SS)](2-) (SS = dimethylethylenedicarboxylate (DMED), toluenedithiolate (tdt), benzenedithiolate (bdt); mnt = maleonitriledithiolate), each possessing two different dithiolene ligands, are synthesized as model of trimethylamine-N-oxide reductase. The asymmetric dithiolene ligands present in these complexes simulate the two different (P and Q) pterin coordinations in the family of DMSO reductase. These complexes reduce trimethylamine-N-oxide ((CH3)3N(+)-O(-) or TMANO), the biological substrate of trimethylamine-N-oxide reductase, to trimethylamine ((CH3)3N), responsible for the fishy smell of dead aquatic animals. The reaction kinetics of trimethylamine-N-oxide reduction by these complexes follow the Michaelis-Menten saturation kinetics. These experimental findings have been rationalized by DFT, TD-DFT level of calculations.

FeW heterometallic complexes, in which an FeX2 (X=Cl, SPh) moiety is attached to monodithiolene oxotungsten through a sulfide bridge, that is, [Ph4P]2[Cl2Fe(S)2WOS2] (), [Ph4P]2[Cl2Fe(S)2WOS2(DMED)] (, DMED=dimethylethylenedicarboxylate), [Ph4P]2[Cl2Fe(S)2WO(tdt)] (, tdt=toluenedithiolate), [Ph4P]2[(SPh)2Fe(S)2WO(tdt)] (), and [Ph4P]2[Cl2Fe(S)2WO(edt)] (, edt=ethanedithiolate), are reported. Mossbauer and EPR spectroscopy, magnetism, electrochemistry, and electronic structural analysis based on DFT and TD-DFT calculations show the transfer of electron from the iron center to the tungsten center, thus resulting in a ferromagnetically coupled FeIIIWV unit, along with antiferromagnetic intermolecular interactions, from the starting FeII and WVI compounds. A net spin of a S=3 ground state, which arises from ferromagnetically coupled FeIII and WV atoms, displays a rare X-band EPR in normal mode at g approximate to 7 in the solid state.

[Et4N]2[Mo(IV)O(mnt)2] (mnt = maleonitriledithiolate) reacts, as a synthon, with Me3SiCN under an acidic medium to produce the square complex [Et4N]4[Mo4(μ-CN)4(mnt)8] (1) in high yield. Complex 1 shows strong antiferromagnetic interactions between adjacent Mo atoms in the cluster. The presence of redox-active mnt as a capping ligand strongly influences the magnetic property of 1. The physicochemical properties of 1 have been rationalized by density functional theory level of calculations.

Synthesis of phosphonodithioato complexes of Mo(IV) and W(IV) bis- dithiolene have been reported. These complexes are characterized by elemental analysis, X-ray crystallography, IR, UV–Vis, 31P NMR, and photoluminescence spectroscopy, electrochemical studies and these results are corroborated by DFT level of calculations. Phosphonodithioato ligands is generated in situ from the reaction of Lawesson’s reagent with mono-oxo Mo/W bis dithiolenes complexes resulting its chelation coupled with oxo transfer reaction from M(IV) bound oxo to {P=S} moiety forming (P=O} group. The new complexes are photoluminescent at room temperature.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Mono(maleonitriledithiolene)sulfidomolybdenum(IV) complex, [MoS(S 4 )(mnt)] 2− ( 2 ; mnt=maleonitriledithiolene) was synthesized by the substitution reaction of a tetrasulfido ligand of the known [MoS(S 4 ) 2 ] 2− ( 1 ) upon reaction with one or even excess equivalent of Na 2 (mnt) in aqueous MeCN solution in air. Surprisingly, 2 undergoes dimerization on treatment with alkyl halide such as MeI and PhCH 2 Br to form bis( μ ‐sulfido)dimolybdenum(V) species, [{MoS(mnt)} 2 ( μ ‐S) 2 ] 2− ( 3 ). These complexes have been characterized by IR, UV/VIS spectroscopy, cyclic voltammetry, elemental analysis, and by X‐ray crystal‐structure analysis. Differences in the relative stability and electrochemical behavior of 1, 2 , and 3 have been correlated with theoretical calculations at DFT level.

Mo-Fe heterometallic complexes with Fe(X)(2) (X = Cl, SPh) moiety attached to monodithiolene oxomolybdenum via sulfur bridge, viz., [Ph(4)P](2)[Cl(2)FeS(2)MoOS(2)(DMED)] (2) (DMED, dimethylethylenedicarboxylate), [Ph(4)P](2)[Cl(2)FeS(2)MoO(tdt)] (3) (tdt, toluenedithiolate) and [Ph(4)P](2)[(SPh)(2)FeS(2)MoO(tdt)] (4) are reported. Mossbauer spectroscopy, magnetism, EPR, electrochemistry and electronic structure based on DFT and TD-DFT calculation show the transfer of electron from iron to molybdenum centre resulting antiferromagnetically coupled Fe(III)Mo(V) unit from the starting Fe(II) and Mo(VI) compounds. A net spin of S = 2 ground state arising from antiferromagnetically coupled Fe(III) and Mo(V) shows a rare X-band EPR in normal mode at g ~ 12 in the solid state. In addition, Mossbauer studies show that electron drifting is more pronounced upon substitution of the chloride ligand by thiophenolate. The changes in dithiolene periphery electronically affect the charge distribution between Mo-Fe in {OMo(μS)(2)Fe} core. DFT calculations indicate that the increasing stability of dative Fe → Mo hetero metal-metal bond in these complexes from 3 to 2 to 4 is related to the extent of electron transfer from the iron to molybdenum centre.