A kinetic approach on hexavalent chromium removal with metallic iron

Sequential Abatement of FeII and CrVI Water Pollution by Use of Walnut Shell-Based Adsorbents

In this study walnut shells, an inexpensive and readily available waste, were used as carbonaceous precursor for preparation of an innovative adsorbent (walnut-shell powder (WSP)) which was successfully tested for the removal of FeII from synthetic acid mine drainage (AMD). Then, the exhausted iron-contaminated adsorbent (WSP-FeII) was recovered and treated with sodium borohydride for the reduction of adsorbed FeII to Fe0. The resulting material (WSP-Fe0) was subsequently tested for the removal of CrVI from aqueous solutions. Treatability batch experiments were employed for both FeII and CrVI-contaminated solutions, and the influence of some important experimental parameters was studied. In addition, the experimental data was interpreted by applying three kinetic models and the mechanism of heavy metal removal was discussed. The overall data presented in this study indicated that fresh WSP and WSP-Fe0 can be considered as promising materials for the removal of FeII and CrVI, respectively. Furthermore, the present work clearly showed that water treatment residuals may be converted in upgraded materials, which can be successfully applied in subsequent water treatment processes. This is an example of sustainable and environmentally-friendly solution that may reduce the adverse effects associated with wastes and delay expensive disposal methods such as landfilling or incineration.

An efficient utilization of chromium-containing vanadium tailings: Extraction of chromium by soda roasting-water leaching and preparation of chromium oxide

Chromium-containing vanadium tailings (CCVT), an industrial waste, were utilized to extract chromium efficiently by soda roasting-water leaching process and for the preparation of highly pure chromium oxide. The effect of extraction of chromium under different roasting and leaching conditions were analyzed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The maximum chromium extraction rate of 91.51% was obtained when soda (Na₂CO₃) and CCVT were mixed in a molar ratio (n (Na₂CO₃)/n (Cr₂O₃)) of 8, roasted at 900 °C and maintained for 120 min. Then, the roasted product was leached in water at 60 °C for 60 min with a liquid-solid mass ratio (L/S) of 10. During soda roasting, the chromium-containing phase (Fe_0.6Cr_0.4)₂O₃ combines with Na₂CO₃ to form Na₂CrO₄, which was then transferred into the leaching liquid, post water leaching. The by-products such as NaFeTiO₄, Na₂CaSiO₄, and Na_0.68Fe_0.68Si_0.32O₂ were left in the leaching residue which was called chromium tailings (CT). 87.40% chromium oxide was recovered from the unpurified leaching liquid after reduction and precipitation by adding Na₂S, followed by roasting the deposit. This process not only relieved the potential threat of the industrial waste CCVT to the environment but also realized the recovery of the valuable element chromium.

Troubleshooting the problems arising from sustainable development

Sustainable development as a concept of societal development encompasses some problems that need to be addressed carefully. They relate to overcoming the technical limits of individual systems, reducing environmental impact, social inclusion, green economic progress involving all stakeholders, limiting the impact of human activities, etc. Over the past few years, as a result of the increasingly pronounced climate change, more and more studies are addressing these problems and stress the importance of sustainable development. The key to sustainable development are, therefore, the solutions to the problems currently encountered by various stakeholders, that together contribute to the preservation of the environment for future generations. This is no longer based on the goodwill of individuals, but has become the responsibility of the entire generation. This article presents some examples of the solutions for the problems arising from sustainable development and is an overview of recent scientific achievements in the field of sustainable development that emerged from recent Sustainable Development of Energy, Water and Environment Systems (SDEWES) conferences. As such, it acts as an editorial paper for the virtual special issue of the Journal of Environmental Management, that is dedicated to the SDEWES2017 conference.

Environmental management as a pillar for sustainable development

There is a growing concern about how to minimize the impact of human activities on the environment. Already nowadays, in some places adaptation efforts are needed in order to avoid the irreversibility of negative human activities. Due to climate changes, and corresponding environmental and social changes, there is a great need for a more sustainable development of mankind. Over the years, research studies that analyzed the sustainable development of different communities with a multi-disciplinary approach, stressed the necessity of preserving the environment for next generations. Therefore, responsible and conscientious management of the environment is a pillar of the sustainable development concept. This review introduction article provides an overview of the recent top scientific publications related to sustainable development that mostly originated from previous SDEWES conferences.