The Red Sea is an arid environment, without riverine inputs, oligotrophic waters and extreme temperature and salinity. Avicennia marina is the dominant vegetation in the shores of the Red Sea. However, little is known about their distribution, dynamics, and services. Therefore, the aim of this Ph.D. was to obtain the basic information needed to evaluate their role in the coastal ecosystems and quantify their services. With that objective we 1) estimated the past and present distribution of mangroves in the Red Sea, 2) investigated the growth, leave production and floration 3) examined the growth limiting factors 4) measured the nutrients and heavy metal dynamics in the leaves and 5) estimated carbon sequestration. We found an increase of about 12% in the last 41 years, which contrasts with global trends of decrease. The extreme conditions in the Red Sea contributed to limit their growth resulting in stunted trees. Hence, we surveyed Central Red Sea mangroves to estimate their node production with an average of 9.59 node y-1 then converted that number into time to have a plastochrone interval of 38 days. As mangroves are taller in the southern Red Sea where both temperature and nutrients are higher than the Central Red Sea, we assessed nutrient status Avicennia marina propagules and naturally growing leaves to find the leaves low in nutrient concentrations (N < 1.5 %, P < 0.09 %, Fe < 0.06) and that nutrients are reabsorbed before shedding the leaves (69%, 72% and 35% for N, P, and Fe respectively). As a result, we conducted a fertilization experiment (N, P, Fe and combinations) to find that iron additions alone led to significant growth responses. Moreover, we estimated their leaf production and used our previous estimates of both the total cover mangrove in the Red Sea along with plastochrone interval to assess their total nutrients flux per year to be 2414 t N, 139 t P and 98 t Fe. We found them to sequester 34 g m-2 y-1, which imply 4590 tons of carbon sequestered per year for the total mangroves covered by the Red Sea.

The aim of this master's thesis is to study the biosorption of heavy metals copper, lead and zinc on thermophilic bacteria of the genus Geobacillus – G. thermodenitrificans CCM 2566 and G. thermocatenulatus CCM 2809. Biosorption was carried out in a batch stirred system for each metal separately. The influence of pH, biomass concentration and initial metal concentration on sorption capacity of bacteria was investigated. For both bacteria the optimum biosorption pH values for copper, lead and zinc were 5; 4 and 5, respectively. Sorption capacity of both bacteria was higher at lower concentrations of biomass and increased with increasing initial metal concentration. The confrontation of sorption capacities showed that the bacterium G. thermocatenulatus has greater sorption potential than G. thermodenitrificans.

The ability of alumino-silicate systems to immobilize hazardous compounds has been investigated since 1990s. The aim of this work is to develope alumino-silicate system (matrix) based on industrial waste products with ability to immobilize hazardous compounds (heavy metals). This ability of the matrix was confirmed by leaching tests based on the law 294/2005 Sb. Concentration of heavy metals in leachates was determined by ICP-MS method. Alumino-silicate system prepared in this work consists of high-temperature fly ash and blast furnace slag activated by mixture of alkaline activators (hydroxide and water glass). Matrixes were characterized by suitable analytic methods (XRD, SEM, FT-IR, DTA-TGA-EGA). The same analytic methods were used to describe the mechanism of immobilization of selected elements (Ba, Cu, Pb) in prepared systems.

Water contaminations by many pollutants, especially heavy metals such as Pb(II), Hg(II), Cu(II), Cd(II), and Cr(VI) pose many public health and environmental concerns as reported in the list of hazardous substances compiled by the US Environmental Protection Agency due to their high toxicity, refractory degradation, and ease of entering food chain. Adsorption by chelating resins is proven to be the most effective method for the extraction of metal ions from polluted and wastewater. However, traditional absorbents such as activated carbon, activated alumina, clay, zeolite, etc., show limited adsorption abilities for these heavy metal ions. The major goal of this thesis is to develop efficient and cost-effective adsorbents for the extraction of heavy metals from wastewater. This dissertation will focus on the development of four chemically modified high surface area adsorbents with accessible chelating sites for capturing and retaining toxic metal ions from polluted water. The first adsorbent, Nitrogen Doped Carboxylated Activated Carbon (ND-CAC), is prepared by a polymerization reaction between melamine and formaldehyde to form the melamine formaldehyde resin (MF-R) followed by carbonization at 800 oC under nitrogen atmosphere to form nitrogen doped carbon (ND-C), and finally oxidation to form the ND-CAC adsorbent. The ND-CAC adsorbent shows high adsorption capacities of 750.5, 250.5, 98.2 mg/g for the extraction of Pb(II), Hg(II), and Cr(VI), respectively from aqueous solutions with a high selectivity to Pb(II). The second adsorbent, Melamine Zirconium Phosphate (M-ZrP) is prepared by a precipitation reaction between Melamine Phosphate (MP) and ZrCl4 in an aqueous solution. The M-ZrP adsorbent is used for the removal of Pb(II), Hg(II), and Cd(II) with maximum adsorption capacities of 680.4, 119.0, and 60.0 mg/g, respectively with a high selectivity to Pb(II). The third adsorbent is chemically functionalized metal organic framework (UIO-66-IT) was prepared by post-synthetic modification using the chelating ligand 2-Imino-4-Thioburit. The adsorbent was used to extract Hg(II) and (HPO4)- ions from aqueous solutions and the results revealed exceptionally high adsorption capacities toward mercury and phosphate ions of 700 and 160 mg/g, placing it among the top functionalized MOF known for the high capacity of Hg(II) removal from aqueous solutions. The fourth adsorbent, Melamine Thiourea Partially Reduced Graphene Oxide (MT-PRGO) prepared by the amidation reaction between chemically modified graphene oxide and melamine thiourea, is used for the effective extraction of Hg(II), Co(II) and Cu(II) from polluted water. The MT-PRGO adsorbent shows exceptional selectivity for the extraction of Hg(II) with a capacity of 651 mg/g, placing it among the top of carbon-based materials known for the high capacity of Hg(II) removal from aqueous solutions. Desorption studies demonstrate that the new adsorbents ND-CAC, M-ZrP, UIO-66-IT, and MT-PRGO are easily regenerated with the desorption of the heavy metal ions Hg(II), Pb(II), Cd(II), and Cr(VI) reaching 99 % - 100 % recovery from their maximum sorption capacities using different eluents. Moreover, all prepared adsorbents showed tremendous abilities to clean contaminated water from toxic heavy metals at trace concentrations. That prove the ability of using them at water contamination level when the concentration of heavy metals is very low. The new adsorbents ND-CAC, M-ZrP, UIO-66-IT, and MT-PRGO are proposed as top performing remediation adsorbents for the extraction of the heavy metals Pb(II), Hg(II), Cd(II), Cr(VI), and (HPO4)- from waste and polluted water.

Philosophiae Doctor - PhD / The risk of increasing global pollution dictates the need to understand environmental processes and develop innovative ways to monitor pollution levels and address associated problems. In order to address this need, this study used a selection of plants leaves (Commelina benghalesis, Paspalum urvillei, Persicaria lapathifolia and Salix babylonica) as biomonitors to assess the state of the environment, more specifically the concentration of certain heavy metal pollutants (Cu, Zn, Fe, Ni, Pb and Cd) of river water and soils in the Eerste River catchment, Western Cape, South Africa.

The objective of this work was the development of an efficient adsorbent for irreversible immobilization of heavy metals in contaminated soils. The adsorbent was prepared by pillaring of montmorillonite with silica followed by grafting of a chelate ligand on its surface. Obtained adsorbent was mesoporous with high content of adsorption sites. Its structure was studied by BET adsorption of N2, dynamic light scattering, and scanning electron microscopy. The adsorption capacity of the organoclay was measured by its mixing with contaminated kaolin and soil samples and by analysis of heavy metal contents in leachate. Deionized water and 50% acetic acid were used for leaching of metals from the samples. As it was demonstrated by the experiments, the adsorbent was efficient in immobilization of heavy metals not only in neutral aqueous media but also in the presence of weak acid. As a result, the adsorbent can be used for reduction of heavy metal leaching from contaminated sites.

The objective of this work was the development of an efficient adsorbent for irreversible immobilization of heavy metals in contaminated soils. The adsorbent was prepared by pillaring of montmorillonite with silica followed by grafting of a chelate ligand on its surface. Obtained adsorbent was mesoporous with high content of adsorption sites. Its structure was studied by BET adsorption of N2, dynamic light scattering, and scanning electron microscopy. The adsorption capacity of the organoclay was measured by its mixing with contaminated kaolin and soil samples and by analysis of heavy metal contents in leachate. Deionized water and 50% acetic acid were used for leaching of metals from the samples. As it was demonstrated by the experiments, the adsorbent was efficient in immobilization of heavy metals not only in neutral aqueous media but also in the presence of weak acid. As a result, the adsorbent can be used for reduction of heavy metal leaching from contaminated sites.

La pollution des eaux usées par les éléments métalliques présents à l’état de traces et les cholorophénols pose un problème majeur pour l’environnement et la santé humaine. Cette étude concerne la synthèse d’argiles organophiles et de zéolithes à partir d’argiles naturelles prélevées en Tunisie et leurs applications pour l’adsorption respectivement des chlorophénols et des cations métalliques (Pb2+, Cd2+).Sur le plan de la synthèse d’argiles organophiles, une argile de type smectitique a été modifiée en utilisant le tensio-actif HDTMA. Cette argile organophile a été utilisée pour l’adsorption du 3-chlorophénol et du 4-chlorophénol. L’étude des isothermes et de la calorimétrie d’adsorption ont prouvé l’efficacité de cette argile organophile pour l’adsorption des deux chlorophénols.Des zéolithes ont été préparées à partir d’une argile naturelle composée de kaolinite, d’illite et de quartz. Ces zéolithes ont été utilisées pour l’adsorption des éléments métalliques tels que la cadmium (Cd2+) et le plomb (Pb2+) . Les cinétiques et les isothermes d’adsorption de Cd2+ et Pb2+ sur les zéolithes synthétisées (CAN, ANA, mélange Faujasite (FAU), néphéline et quartz), une cancrinite naturelle, une zéolithe commerciale (FAU 13X) et l’argile de départ ont été étudiées à 25°C en utilisant la méthode des restes. Une étude calorimétrique a été faite pour mieux comprendre les phénomènes mis en jeu lors de l’adsorption. La cinétique d’adsorption est très rapide. Une meilleure affinité est obtenue pour les zéolithes. / This study concerns the synthesis of zeolites and organophilic clays from clay and their applications for the adsorption of metallic elements (Pb2+, Cd2+) and chlorophenols.In terms of the synthesis of organophilic clays, a smectite clay was modified using the HDTMA surfactant. This organophilic clay was used for the adsorption of 3-chlorophenol and 4-chlorophenol. The study of isotherms and adsorption calorimetry have proved the effectiveness of this organophilic clay for the adsorption of the two chlorophenols.By hydrothermal high-pressure synthesis of zeolites, from natural clay composed of a fraction of kaolinite, illite and quartz, two types of zeolites were synthesized with good purity, a cancrinite (CAN) type zeolite and the other analcime (ANA) type; other type of zeolite was synthesized such as faujasite 13X but the purity and reproducibility was limited.These three types of zeolite (CAN, ANA and FAU 13X) were tested for the adsorption of Pb (II) and Cd (II). A better affinity of the zeolites synthesized than the starting clay with respect to the two metallic cations (Pb (II) and Cd (II)). The study of the adsorption kinetics of Pb (II) and Cd (II) showed rapid adsorption of the two metallic cations studied on the different types of zeolites. The results proved that the synthesized zeolites were a very promising materials for the adsorption and removal of heavy metals in water.

Algae are microscopic organisms with a great potential to produce biomass and lipids at productivities several times higher than terrestrial crops. To grow, these organisms consume carbon dioxide (CO2), a greenhouse gas. This gas, emitted primarily by power plants after coal burning, can be effectively used for algae production, thus resulting in CO2 remediation and biomass beneficial utilization as feedstuff, industrial filler and biodiesel feedstock. However, since coal is a fuel mined from the earth’s crust, it contains heavy metals that are released during coal burning and inevitably enter the algal cultivation system, contaminating the water were algae is grown, the algal biomass and the products derived from such biomass. The distribution of heavy metals from flue gas in algal cultivation systems is unknown, yet necessary to advance this industry. This study focused on quantifying the distribution and effects that ten coal-derived heavy metals (Cu, Co, Zn, Pb, As, Se, Cr, Hg, Ni and Cd) will have on algae strain Scenedesmus obliquus and on the potential products derived from this algae.

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