Ali Sdiri

Effects of impurities on the removal of heavy metals by natural limestones in aqueous systems.

Effects of impurities on the removal of heavy metals by natural limestones in aqueous solutions were studied by evaluating various factors including limestone concentration, pH, contact time and temperature. Solutions of Pb(II), Cd(II), Cu(II) and Zn(II), prepared from chloride reagents at a concentration of 10 mg/L, were studied in a batch method. Four natural limestone samples, collected from the Campanian-Maastrichtian limestone beds in Tunisia, were used as adsorbents. Sorption experiments indicated that high removal efficiencies could be achieved. Limestone samples containing impurities, such as silica, iron/aluminum oxides and different kinds of clay minerals, demonstrated enhanced sorption capacity, nearing 100% removal in some cases. Kinetic experiments showed that the sorption of metal ions occurred rapidly at a low coverage stage, and that solutions were nearly at equilibrium after 60 min. Data trends generally fit pseudo-second order kinetic, and intra-particle diffusion, models. The following conditions were found to promote optimum, or near-optimum, sorption of heavy metals: 1) contact time of more than 60 min, 2) pH = 5, 3) >3 g/L limestone concentration and 4) T = 35 °C. The results of this study suggest that the limestones from northern Tunisia, that contain higher amounts of silica and iron/aluminum oxides, are promising adsorbents for the effective removal of toxic heavy metals from wastewaters.

Re-evaluation of several heavy metals removal by natural limestones

Different treatment technologies have been efficiently applied to remove heavy metals from wastewater. Efforts have been made to find out the most economic water treatment technology by using low cost and easily accessible natural materials. On the other hand, heavy metals are the most threatening groundwater contaminants because of their toxicity and harmful effects on human and biota. This review discusses the use of natural geological materials for heavy metal removal in aqueous systems. Special attention has been devoted to natural limestone through a systematic inventory of relevant published reports. The removal of toxic metals may include different mechanisms (e.g., physisorption, chemisorptions, precipitation, etc.), depending on the physico-chemical properties of the material and the removed metal. Sorption of toxic metals (e.g., Pb, Cu, Cd, Zn, Cr, Hg, etc.) onto natural limestone involved precipitation of metal carbonate as a predominant removal process, but often subordinated by adsorption and ion exchange, depending on the physico-chemical properties of the studied limestone.

Late Cretaceous and Palaeocene clays of the northern Tunisia: potential use for manufacturing clay products

Late Cretaceous and Palaeocene clay deposits of the northern Tunisia were studied for potential valorization in clay product manufacturing. To achieve this goal, physicochemical characterization based on multidisciplinary approaches including mineralogy, geochemistry and thermal analyses was carried out. Clay samples collected from the Bir M’Cherga and Tajerouine study sites have undergone chemical analysis by using atomic absorption spectroscopy. The obtained results showed that the studied samples were mainly composed of silica, alumina, calcium and iron oxide. Mineralogical analysis confirmed the results of chemical analysis; it showed the main peaks of quartz, calcite, kaolinite, smectite and illite. Those clay samples were used as natural resources for manufacturing earthenware tiles. Mixtures of clays and dolomites were prepared from the Late Cretaceous and Palaeocene clays and then heated to the desired temperature to obtain different earthenware products. Finally, the prepared clay products were tested via different geotechnical analyses. It was found that the clay percentage needed to be decreased in the starting mixture to enhance the properties of the final products. Those results also indicated that industrial application of both Late Cretaceous and Palaeocene clays of the northern Tunisia could be done, especially for manufacturing clay products.

An Experimental Design for the Optimization of Brick Manufacturing Procedure: Application on the Late Miocene Clays, Southern Tunisia

Clay deposits of the Segui formation (Jebel Stah of the Gafsa basin, Southwestern Tunisia) were used as natural material for brick manufacturing. Factors influencing the preparation procedure were optimized by an experimental design to find out the most propitious conditions for the preparation of bricks of high quality. The collected clay samples were characterized by various techniques, including X-ray diffraction (XRD), Fourier transform infrared (FTIR) and pycnometry. The optimum conditions for the preparation of high quality materials were investigated by studying the effects of clay minerals percentage, sintering time and temperature. Then various tests including sintering shrinkage, water absorption and compressive strength of the newly prepared brick samples were evaluated to determine the optimum preparation conditions. Results showed that the optimized conditions were: 80% illite, 830°C sintering temperature and 2 h sintering time. The same results showed that brick shrinkage depended mainly on water absorption, illite and smectite percentages. These results suggested that clay samples from Jebel Stah are promising natural materials that could be used to prepare bricks with better mechanical properties.

Reconstruction of the Late Cretaceous-Paleocene paleoenvironment (northern Tunisia) from biostratigraphy, geochemistry and clay mineralogy

A multidisciplinary approach was adopted for the reconstitution of the depositional environments based on clay minerals distribution, biostratigraphy and geochemical properties of the Late Cretaceous-Paleocene deposits. Evolution of the mineralogical compositions (i.e. clay minerals contents) was ascertained in two cross sections from the Late Cretaceous and Paleocene belonging to different paleogeographic domains: the Bir M’Cherga (Tunisian Dorsal) and Tajerouine (Northern West of Tunisia) study sites. Chemical analysis of the original clay samples, collected in both sites (i.e. Late Cretaceous and Paleocene clays), showed significant amounts of oxides including calcium, silica, alumina and iron. Three distinct mineralogical zones were identified. Clay mineral assemblages of the Late Cretaceous showed the predominance of kaolinite, subordinated by variable proportions of illite and smectite. In contrast, those of Paleocene clearly showed the predominance of smectite to the detriment of kaolinite and illite. The predominance of kaolinite in the Late Cretaceous clay deposits indicated a calm and shallow depositional environment influenced by hot and wet climate, especially in northeastern Tunisia (Bir M’Cherga study site). Kaolinite typically forms under lacustrine environment where appreciable movement of water would be expected, leading to the development of kaolinite. During Paleocene, the smectite-enriched mineralogical sequence suggested similar climatic conditions with further deepening of the depositional environment in salt lakes. The regional geodynamic context of both sections showed an important Maastrichtian unconformity with a Paleocene major hiatus extending from the East to the West.

Water resource management for sustainable development

Water resource management is the cornerstone for sustainable development. According to the United Nations world water development report, one-fifth of the world’s population lives in areas characterized by physical water scarcity (Xu et al. 2018). The increase of water demand concomitantly with water scarcity is a common threat for humanity; it is expected to be worse in the future. Almost half of the world population will be living in area with high water stress by 2030 (United Nation Department of Economic and Social Affairs 2012). Thus, potential water resources need to bemonitored with care for strategic management. Population growth and economic development cause significant increase in agricultural and industrial demand for water. Recently, Guerra and Reklaitis (2018) addressed the growing vulnerability to both availability and quality of water sources. They stated that Bthe vulnerability of energy systems to water utilization constraints could be mitigated by the effective design and implementation of water management strategies.^ This was consistent with main target of the 2 International Conference on Integrated Environmental Management for Sustainable Development (ICIEM), held in Sousse-Tunisia from 27 to 30 October 2016 because water management issues require more attention by the research community, especially in arid/semi-arid countries. The integration of wastewater quality and vulnerability into the design and planning of water management strategies are needed. Numerous researchers have addressed the strategic topic of water resource management, especially for agriculture (Al-Saidi 2017; Christ and Burritt 2017; Gao et al. 2017; Liu et al. 2017; Nguyen et al. 2018; Ross 2017; Skouteris et al. 2018; Zhou et al. 2017). It is well known the agriculture accounts for more than two thirds of the global water use (Kraiem et al. 2014). This situation may induce severe water crisis and all waters even those of bad quality have to be valued and stored. Therefore, integrated water management is one of the pillars of sustainable development. In this context, the 2 ICIEM conference aimed at exchanging relevant experiences, up-to-date scientific research, and findings carried out all over the world to protect and preserve the environment through rationalizing water resources. More than 300 participants attended this event to share new findings and discuss the potential applications of such new processes that can be turned out to viable technique for sustainable development. This thematic issue includes selected papers from the conference acting in the field of water resources. They have, undoubtedly, contributed to deepen knowledge on the current researches and achievements in the broad field of water resources. The main aspects are the following: water quality and sustainable use, integrated water resources management, assessment of groundwater vulnerability, the quantity and quality of water streams, the potential for the treatment of these waters for recycle and/or beneficial reuse and the economics of such treatment strategies and management of irrigation water and durability. Fruitful exchange between researchers during the conference alongside the peer review process clearly showed their common concern to address the problem of water management for the sake of sustainable development. Few problems may be specific to a given region, but similarity in the diagnosis as well as the remediation approaches demonstrated that This article is part of the Topical Collection on Water Resource Management for Sustainable Development

Integrated management of the environment for sustainable development

In recent years, environmental protection has emerged as a requirement that goes beyond the state borders to reach a global dimension. This awareness has resulted in numerous treaties, directives, and conventions and even changed the way we do business. Protection of the environment, one of the pillars of sustainable development, is an absolute priority for the international community. In this context, the focus on relevant experiences, up-to-date scientific research and findings carried out all over the world to protect and preserve the environment and can enhance our awareness about environmental protection. Strategies and pollution management tools are of great importance for stakeholders and decision makers. Water treatment and management relates to all the processes used to purify water including traditional processes such as decantation, filtration, and adsorption, and of the specific processes where one carries out some chemical reactions to facilitate the treatment of this waste (precipitation/filtration). Rapid industrialization and urbanization have resulted in the deterioration of water, air, and land quality (Sdiri and Bouaziz 2014). Various industrial activities including textile dyeing, fertilizer production, and mining activities generate high volume of contaminated wastewaters (Klay et al. 2010; Lim and Aris 2014; Watlington 2005). The tremendous increase in the use of contaminants over the past few decades has eventually resulted in an increased flux of toxic substances in the environment. Various methods were proposed for wastewater treatments; they including ion exchange resins (Fu and Wang 2011; Iqbal et al. 2009), solvent extraction (Sadegh Safarzadeh et al. 2007), electrochemical treatment (Sulaymon et al. 2011), and biosorption (Ahmad et al. 2010; Das 2012). Among those techniques, adsorption was the most preferred technique due to its simplicity and relatively low cost (Ali and Gupta 2007; Bhattacharyya and Gupta 2008; Itskos et al. 2010; Jaman et al. 2009). Efforts are being done to find out the most economic water treatment technology. Sustainable development has become a slogan for both developed and developing countries; it is now becoming a prerequisite for the appropriations granted to the countries. If the credit will contribute to the sustainable development, it will be easily granted because the progress of a nation is conditioned by the sustainable development indices. This inevitable condition measure the development of a community or a country. Currently, most of the new techniques for wastewater treatments take into account such a factor. Special attention was given to the sustainable development as a main topic of the current integrated environment management meeting. The success of a new advanced technique applied for the treatment of water; ground and air can be highly efficient if it consider sustainable development indices. Thus, in all the processes of water treatment, the aspect of the sustainable development is of significant positive impact on the environment (Muga and Mihelcic 2008). Responsible Editor: Philippe Garrigues

Heavy metals’ mobility from phosphate washing effluents discharged in the Gafsa area (southwestern Tunisia)

Wet processing of natural phosphate to increase the P2O5 content and eliminate non-desired fraction (both coarse and fine fractions) took place in various laundries of the Gafsa-phosphatic area. Effluents of those laundries often contain various contaminants that are directly discharged to the receiving waterbody, representing a serious threat to the environment. Physico-chemical characterization of those effluents showed elevated levels of sulfates, fluorine, and metals. The bordering land showed gypseous soils. Those soils are covered by the discharged phosphate-washing sludge. The effect of which on the structure and the permeability of the soils seemed to be significantly harmful. Batch tests were conducted to evaluate the mobility of various metals on the surrounding area of phosphate laundries. Leaching results revealed low cadmium and uranium mobilities. However, Cd concentrations in the studied samples leached from soils exceeded the standards. This suggested the contamination by cadmium.