Effect of hydraulic binders' addition on trace metals stabilization in the S/S process of dredged sediments

The Solidification/Stabilization method for dredged sediments remediation can be very effective for the immobilization of trace metal (TM) pollutants. The ordinary Portland cement (OPC) is largely used in this process. Nevertheless, the mechanical performance of treated sediments can be considerably improved at long term using ground granulated blast furnace slag (GGBS) as was shown in (Gutsalenko et al., 2018). Therefore, it is worth investigating whether this new binder is also relevant in terms of stabilization and mechanisms involved in this process. To meet this objective, leaching test, total attack, sequential extraction (SE) and X-ray Adsorption Near-Edge Structure (XANES) experiments measurements were performed. The results of the leaching tests conducted as part of the study are promising for the use of GGBS in the treatment of the real case project Dublin sediment and it outperforms the OPC-based treatment.. The sequential extraction method was applied to evaluate the potential risks of toxic elements according to their repartition in the Dublin sediment matrix and predicts the release of metals under different environmental conditions. It shows a lower perturbation rate of pollutants with the GGBS-based binder. Finally, XANES experiments demonstrate changes in the chemical environment of Zn and Cu after the treatment of the sediment with OPC compared to the GGBS rich binder. Consequently, this study finds that it is more pertinent to use the GGBS-based binder in terms of trace metal stabilization.

Insight into the branched alcohol formation mechanism on K–ZnCr catalysts from syngas

The first C–C bond formation is from the reaction of CO and CHO (formyl) on the K–ZnCr catalysts.

Status and prospects in higher alcohols synthesis from syngas

Higher alcohols are important compounds with widespread applications in the chemical, pharmaceutical and energy sectors. Currently, they are mainly produced by sugar fermentation (ethanol and isobutanol) or hydration of petroleum-derived alkenes (heavier alcohols), but their direct synthesis from syngas (CO + H₂) would comprise a more environmentally-friendly, versatile and economical alternative. Research efforts in this reaction, initiated in the 1930s, have fluctuated along with the oil price and have considerably increased in the last decade due to the interest to exploit shale gas and renewable resources to obtain the gaseous feedstock. Nevertheless, no catalytic system reported to date has performed sufficiently well to justify an industrial implementation. Since the design of an efficient catalyst would strongly benefit from the establishment of synthesis-structure-function relationships and a deeper understanding of the reaction mechanism, this review comprehensively overviews syngas-based higher alcohols synthesis in three main sections, highlighting the advances recently made and the challenges that remain open and stimulate upcoming research activities. The first part critically summarises the formulations and methods applied in the preparation of the four main classes of materials, i.e., Rh-based, Mo-based, modified Fischer-Tropsch and modified methanol synthesis catalysts. The second overviews the molecular-level insights derived from microkinetic and theoretical studies, drawing links to the mechanisms of Fischer-Tropsch and methanol syntheses. Finally, concepts proposed to improve the efficiency of reactors and separation units as well as to utilise CO₂ and recycle side-products in the process are described in the third section.

Binary ZnO/Zn–Cr nanospinel catalysts prepared by a hydrothermal method for isobutanol synthesis from syngas

A series of binary ZnO/Zn–Cr nanospinel catalysts were prepared by a hydrothermal method and applied in direct synthesis of isobutanol from syngas, during which the effect of the hydrothermal time/temperature on their catalytic performance in the isobutanol synthesis has been investigated at 400 °C and 10 MPa.

The role of potassium promoter in isobutanol synthesis over Zn–Cr based catalysts

The potassium promoter would tailor the microstructure of the Zn–Cr spinel and stabilize the surface hydroxyl species which greatly facilitate the formate of isobutanol.