Volume 3, Issue 1

The unique chemical and physical properties of metals mean that they are extensively utilized by industry in a huge variety of applications, including electronics, materials, industrial catalysts and chemicals. The increased consumer demand from a growing population worldwide with rising aspirations for a better life has resulted in concerns over the security of supply and accessibility of these valuable elements. As such, there is a growing need to develop alternative methods to recover them from waste repositories, current or historic, both for hazard avoidance and potentially, as a new source of metals for industry. Phytoextraction (the use of plants for the recovery of metals from waste repositories) is a green and novel technique for metal recovery, which, if done with the goal of resource supply rather than hazard mitigation, is termed “phytomining”. The ability for plants to form metallic nanoparticles as a consequence of phytoextraction could make the recovered metal ideally suited for utilization in green chemical technologies, such as catalysis. This review focuses on a multidisciplinary approach to elemental sustainability and highlights important aspects of metal lifecycle analysis, metal waste sources (including mine tailings), phytoextraction and potential green chemical applications that may result from the integration of these approaches.

The increasing interest in biocatalytic processes means there is a clear need for a new systematic development paradigm which encompasses both protein engineering and process engineering. This paper argues that through the use of a new microfluidic platform, data can be collected more rapidly and integrated with process modeling, can provide the basis for validating a reduced number of potential processes. The miniaturized platform should use a smaller reagent inventory and make better use of precious biocatalysts. The EC funded BIOINTENSE project will use ω-transaminase based synthesis of chiral amines as a test-bed for assessing the viability of such a high throughput biocatalytic process development, and in this paper, such a vision for the future is presented.

The urgent need for a radical conversion of chemical production is described in the context of the drastic violation of time scales for the natural regeneration of resources. Besides renewable energy sources, we need a transition to a completely sustainable production and application of materials and other substances. Decentralized chemical facilities, microreaction technology, and the coupling between energy conversion and chemical conversion will play a crucial role in this process. All these developments must be connected with the ongoing natural global entropy export system. Some general examples for the required future developments in chemical technologies are given and discussed against a background of a vision of a complete sustainable substance management in the future and a technological sustainability in the industrial transition process where powerful bridging technologies are used.

Novel eco-friendly methods for the synthesis of metal nanoparticles are preferred and have recently been widely researched. In this study, a cost-effective and environmentally friendly method for the synthesis of gold nanoparticles was investigated. Costus pictus , also known as insulin plant due to its antidiabetic activity, was used as the reducing agent. Chloroaurate ions were rapidly reduced by the methanolic extract of Costus pictus , which was indicated by the color change from yellow to ruby red. The presence of a peak at 530 nm in UV-visible spectrophotometry confirmed the reduction of chloroaurate to gold nanoparticles. The reaction kinetics and effects of time, temperature, concentration of extract and substrate were also studied. The size and morphology of gold nanoparticles were analyzed using scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HR-TEM) and they were found to be cuboidal, with a size of around 20 nm. The size of the particles was also analyzed by the particle size analyzer, and was found to be 45 nm. These particles were functionalized with bisdemethoxycurcumin analog (BDMCA). X-ray diffraction (XRD) analysis of prepared nanoparticles showed that the gold nanoparticles have a face centered cubic structure and that of functionalized nanoparticles showed peaks similar to that of BDMCA. Fourier transform infrared spectroscopy (FTIR) studies revealed the presence of reducing groups in the plant methanolic extract and the functionalization of nanoparticles with BDMCA was also confirmed. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay showed that, the BDMCA-functionalized gold nanocubes possess anticancer activity. The mechanism of action is discussed.

The microreactor has been developed for a wide range of applications because of many advantages, such as high mass transfer efficiency, low energy consumption and the closed and safe system. The application of microreactors in the traditional hydrometallurgy extraction process is expected to overcome difficulties such as co-extraction of impurities, large consumption of extractant and hidden fire risks. In this study, the extraction and separation efficiency of In 3+ from a complex sulfate solution containing impurities, such as Fe 2+ and Zn 2+ , were studied. The microreactor extraction was carried out in a Pyrex microchip, and the organic phase was prepared with the extractant di(2-ethylhexyl) phosphoric acid (D2EHPA) diluted in 260# kerosene. The results showed that with only 0.55 s contact between the organic and aqueous phases, the extraction ratio of In 3+ can reach 90.80%, while only 0.16% of Fe 2+ and 0.22% of Zn 2+ were co-extracted; the average mass transfer speed of In 3+ was calculated as high as 0.34 g·m -2 ·s -1 . Compared with the traditional mixing settler process, microreactor extraction has advantages of higher extraction ratio of In 3+ , lower trend of co-extraction of the impurities and emulsification.

Pretreatment of sunflower hulls was conducted under varied dilute acid concentrations (0.5–2.0 wt%), reaction temperatures ranging between 140°C and 160°C and the reaction time up to 30 min. The conversion of xylan into xylose and furfural was investigated. The maximum xylose and furfural recoveries, 54.5±0.7 and 24.0±1.1 wt%, respectively, were obtained at different reaction times with 2.0 wt% acid concentration at 160°C. The experimental data were fitted into a two-step kinetic model based on irreversible pseudo-first-order kinetics at each step. The model was successfully validated using the F-test. Sunflower hulls showed a greater recalcitrance to acid pretreatment than other agricultural crops, such as kenaf, sorghum and sunn hemp. This feature was ascribed to the occurrence of a wax layer on the cell wall surface with a high lignin content, which may act as a barrier hindering the acid access to acetyl linkages in xylan.