Phytoextraction is one of the most promising phytotechnologies used to restore natural environments degraded by mining activities. In New Caledonia, a few plant species, which belong to the Grevillea genus, have the ability to extract Mn from soil and accumulate it in abundance (over 1 % of leaves dry weight). This review describes the use of Grevillea Mn‐accumulating plant species to produce the first bio‐sourced Mn catalysts, called Eco‐Mn catalysts. Extensive structural studies of Eco‐Mn catalysts have highlighted an original composition characteristic of their vegetal origin. Eco‐Mn catalysts have demonstrated competitive catalytic activities compared to conventional Mn catalysts in Lewis acid catalysis, aminoreductions, alcohol oxidations, epoxidation reactions, oxidative cleavage of 1,2‐diols and alkenes and “Janus catalysts” for sequential tandem oxidations such as tandem carbonyl‐ene cyclisation, synthesis of substituted pyridines and oxidative iodination of ketones.

A new sustainable method is reported for the formation of aromatic carbon–heteroatom bonds under solvent‐free and mild conditions (no co‐oxidant, no strong acid and no toxic reagents) by using a new type of green ionic liquid. The bromination of methoxy arenes was chosen as a model reaction. The reaction methodology is based on only using natural sodium bromine, which is transformed into an electrophilic brominating reagent within an ionic liquid, easily prepared from the melted salt FeCl3 hexahydrate. Bromination reactions with this in‐situ‐generated reagent gave good yields and excellent regioselectivity under simple and environmentally friendly conditions. To understand the unusual bromine polarity reversal of sodium bromine without any strong oxidant, the molecular structure of the reaction medium was characterised by Raman and direct infusion electrospray ionisation mass spectroscopy (ESI‐MS). An extensive computational investigation using density functional theory methods was performed to describe a mechanism that suggests indirect oxidation of Br− through new iron adducts. The versatility of the methodology was successively applied to nitration and thiocyanation of methoxy arenes using KNO3 and KSCN in melted hexahydrated FeCl3.

An innovative methodology was implemented for removing arsenic from aqueous solution by developing successive biosorption experiments. Considering the high affinity of As oxyanions toward Fe(III) oxides, the biosorption of Fe(II) was first conducted using nine biomaterials-aquatic and terrestrial invasive species, biowastes, local plants. Pistia stratiotes, an invasive alien species presenting the highest concentration of adsorbed Fe(II), was selected for a detailed investigation of As(V) removal from wastewater. After oxidation of the biosorbent into Fe(III), it yielded to a 92% removal efficiency determined by GFAAS and an excellent maximum biosorption capacity of 5.1 mg.g −1 . The biosorbent was characterized by MP-AES and HRTEM-EDX. The adsorption mechanisms for iron and arsenic have been studied via theoretical models and the Langmuir isotherms and pseudo-second-order kinetics models revealed excellent linearity and highlighted the robustness of the method. These promising results were developed to build a pilot for As(V) removal from the Russec river (Orbiel Valley, France), polluted with arsenic.