Treatment of Tannery Effluent of Unit Bovine Hides’ Unhairing Liming by the Precipitation

The tannery effluents are characterized by high toxic pollutants such as sulfides; used in the tanning of animal’s skin. The mean objective of this work is the evaluation of the pollution degree of various operating units, and the treatment of tannery effluent generated from unhairing-liming unit. According to physicochemical characterization, this effluent was largely basic and very loaded in sulfides, which have harmful effects on human health and the environment as well. Otherwise, the microbiological characterization showed an absence of pathogenic bacteria and a low concentration of mesophilic aerobic flora, because of this effluent toxicity. Thus, the treatment of this effluent is indispensable before its reject into the environment. In fact, chemical precipitation is a promising approach for the treatment of this effluent. In this regard, ferric chloride was used as chemical agent to reduce and removal sulphide ions from this effluent. As result, this treatment gave an excellent abatement rate of sulphide, which reached more than 90% using a pH of 8.5 and a ferric chloride concentration of 1.4 mol/L.

Colloidal sulphur production by electrochemical oxidation of sulphide in a swirling flow reactor

A cylindrical reactor with swirling flow is tested for the production of colloidal sulphur via the oxidation of sulphide ions with a concentration of 2 g dm−3 in alkaline solutions...

Does the crystal structure of vanadium nitrogenase contain a reaction intermediate? Evidence from quantum refinement

Recently, a crystal structure of V-nitrogenase was presented, showing that one of the µ2 sulphide ions in the active site (S2B) is replaced by a lighter atom, suggested to be NH or NH2, i.e. representing a reaction intermediate. Moreover, a sulphur atom is found 7 Å from the S2B site, suggested to represent a storage site for this ion when it is displaced. We have re-evaluated this structure with quantum refinement, i.e. standard crystallographic refinement in which the empirical restraints (employed to ensure that the final structure makes chemical sense) are replaced by more accurate quantum–mechanical calculations. This allows us to test various interpretations of the structure, employing quantum–mechanical calculations to predict the ideal structure and to use crystallographic measures like the real-space Z-score and electron-density difference maps to decide which structure fits the crystallographic raw data best. We show that the structure contains an OH−-bound state, rather than an N2-derived reaction intermediate. Moreover, the structure shows dual conformations in the active site with ~ 14% undissociated S2B ligand, but the storage site seems to be fully occupied, weakening the suggestion that it represents a storage site for the dissociated ligand. Graphic abstract

Generation of 34S-substituted protein-bound [4Fe-4S] clusters using 34S-L-cysteine

The ability to specifically label the sulphide ions of protein-bound iron–sulphur (FeS) clusters with 34S isotope greatly facilitates structure–function studies. In particular, it provides insight when using either spectroscopic techniques that probe cluster-associated vibrations, or non-denaturing mass spectrometry, where the ∼+2 Da average increase per sulphide enables unambiguous assignment of the FeS cluster and, where relevant, its conversion/degradation products. Here, we employ a thermostable homologue of the O-acetyl-l-serine sulfhydrylase CysK to generate 34S-substituted l-cysteine and subsequently use it as a substrate for the l-cysteine desulfurase NifS to gradually supply 34S2− for in vitro FeS cluster assembly in an otherwise standard cluster reconstitution protocol.

Influence of Sulphides on Hydration of Ground Granulated Slag Alkali Activated Mortars and Pastes

Influence of sodium sulphide on properties of sodium hydroxide activated ground granulated blast furnace slag was investigated. Properties of both fresh (cone flow, density) as well as hardened (compressive strength) mortars were determined. Early hydration of pastes was investigated using conducting calorimetry. Results showed, that introduction of sodium sulphide to caustic soda activated slag only slightly influence the course of hydration process. Early strength is increased by about 10%. In later periods strength is virtually not affected by the presence of sodium sulphide. Those observations are confirmed by calorimetric results. Presence of sodium sulphide causes slight decrease in consistency of mortars. Colour of mortars is also affected by the presence of sulphides. It is more darker and it is most probably due to the reducing properties of sulphide ions. Results of model investigations on precipitated C-S-H phase showed, that presence of sulphides results in increased main basal spacing of C-S-H phase as determined by XRD.

ELECTROCHEMICAL BEHAVIOR OF ELECTRODEPOSITED NANOCRYSTALLINE COBALT-IRON ALLOY COATING IN DIFFERENT PH

The electrochemical behavior of a cobalt-iron (CoFe) alloy electrode in 0.1 M Na2SO4 (sodium sulphate) aqueous solution of different pH was investigated. The presence of a different concentration of dissolved sulphide ions with different pH on the corrosion of electrodeposited cobalt-iron was investigated using the EQCM technique. The corrosion rates of the alloys in acidic solutions are pronouncedly high, compared to those measured in neutral or basic solutions. The presence of sulphide ions accelerates markedly the anodic reaction for all deposits in the basic medium. The dissolution rate was twice two times faster when S2− was added. By employing the EQCM, it was observed that the mass decrease or dissolution rate was significant with an increase in pH concentration.