Evaluation of the potential of two halophytes to extract Cd and Zn from contaminated saltwater.

The contamination of saltwater by toxic heavy metals has become a worldwide problem. The application of phytoextraction to remove these pollutants seems to be more efficient and cheaper compared to physicochemical methods. In this work, we evaluated the potential of two halophyte species to accumulate cadmium and zinc from contaminated water. Seedlings of Carpobrotus edulis L. and Sesuvium portulacastrum L. were cultivated during 1 month on pots filled with saltwater (200 mM NaCl) containing different concentrations of Cd2+ (0, 50, 100 µM) and of Zn2+ (0, 200, and 400 µM) applied separately. Results showed that both halophytes were more resistant to Zn2+ than Cd2+ and that Sesuvium better tolerates the two metals. Zn2+ and Cd2+ concentrations in the shoot as well as the values of translocation factors suggest that these species are able to absorb and to concentrate Cd2+ and Zn2+ in their roots and shoots. Hence, after 1 month of culture on 50 µM Cd2+, plants were able to extract 31% and 21% of Cd, respectively, in S. portulacastrum and C. edulis. The Zn-extraction efficiency was less important and reached 18 and 19%, respectively, in S. portulacastrum and C. edulis cultivated under 200 µM Zn2+. Given together, data demonstrate the efficiency of the use of halophytes, especially S. portulacastrum, to extract Zn2+ and Cd2+ from salt wastewater.

Canine Leishmania spp. infection in two distinct foci of visceral and cutaneous leishmaniasis in Tunisia.

Visceral leishmaniasis (VL) and zoonotic cutaneous leishmaniasis (ZCL) caused by Leishmania (L.) infantum and L. major, respectively, are endemic in Tunisia. The aim of the study was to assess canine Leishmania spp. infection prevalence as well as to identify the Leishmania species involved in two well-documented and geographically distinct VL and ZCL foci. One hundred seventy-six dogs were randomly recruited in the VL focus of Sbikha-Zaghouan (n = 100) and the ZCL focus of Echrarda-Nasrallah (n = 76). Physical examination and blood collection were systemically performed. Needle aspiration was done in case of lymph node (LN) enlargement. All sera were tested by ELISA. kDNA RT-PCR was performed on DNA extracts from (i) buffy coats of seropositive dogs and (ii) LN aspirates. Leishmania species identification was done by ITS1 PCR-sequencing. Thirty-three dogs (18.8%) were infected by Leishmania; 30 having anti-Leishmania antibodies and 3 were seronegative dogs with Leishmania DNA in LN aspirates. Prevalence of infection was significantly higher in VL foci than in ZCL foci (27% versus 7.9%, p = 0.002). Leishmania species was identified in 11 dogs and corresponded to L. infantum. Combination of serology and qPCR on LN aspirates seems to be the best option for canine leishmaniasis diagnosis. Infection is more frequent in VL foci and L. infantum is the only identified species.

Alginate/geopolymer hybrid beads as an innovative adsorbent applied to the removal of 5-fluorouracil from contaminated environmental water.

Water contaminated by cytostatic drugs has many negative impacts on the ecosystems. In this work, cross-linked adsorbent beads based on alginate and a geopolymer (prepared from an illito-kaolinitic clay) were developed for a promising decontamination of the 5-fluorouracil (5-FU) cytostatic drug from water samples. The characterization of the prepared geopolymer and its hybrid derivative was performed by scanning electron microscopy, X-ray diffraction, Fourier transform infrared and termogravimetric analysis. Batch adsorption experiments indicated that alginate/geopolymer hybrid beads (AGHB) allow an excellent 5-FU removal efficiency of up to 80% for a dosage adsorbent/water of 0.002 g/mL and a concentration of 5-FU of 2.5 mg/L. The adsorption isotherms data follow well the Langmuir model. The kinetics data favor the pseudo-second-order model. The maximum adsorption capacity (qmax) was 6.2 mg/g. The optimal adsorption pH was 4. Besides pore filling sorption process, the carboxyl and hydroxyl groups from alginate immobilized onto the geopolymer matrix favored the retention of 5-FU ions by hydrogen bonds. Common competitors, such as dissolved organic matter, do not significantly affected the adsorption. In addition, this material has not only eco-friendly and cost-effective advantages but also excellent efficiency when applied to real environmental samples such as wastewater and surface water. This fact suggests that it could have a great application in the purification of contaminated water.

Easy separable, floatable, and recyclable magnetic-biochar/alginate bead as super-adsorbent for adsorbing copper ions in water media.

This work aimed to develop innovative material by combining properties of magnetic-biochar (derived from peanut shells) and hydrogel bead (MBA-bead) and apply it for adsorbing Cu2+ in water. MBA-bead was synthesized by physical cross-linking methods. Results indicated that MBA-bead contained ∼90% water. The diameter of each spherical MBA-bead was approximately 3 mm (wet form) and 2 mm in (dried form). Its specific surface area (262.4 m2/g) and total pore volume (0.751 cm3/g) were obtained from nitrogen adsorption at 77 K. X-ray diffraction data confirmed Fe3O4 presented in magnetic-biochar and MBA-bead. Its Langmuir maximum adsorption capacity for Cu2+ was 234.1 mg/g (30 °C and pHeq 5.0). The change in standard enthalpy (ΔH°) of the adsorption was 44.30 kJ/mol (dominant physical adsorption). Primary adsorption mechanisms were complexation, ion exchange, and Van der Waals force. Laden MBA-bead can be reused several cycles after desorbing with NaOH or HCl. The cost was estimated for producing PS-biochar (0.091 US$/kg), magnetic-biochar (0.303-0.892 US$/kg), and MBA-bead (1.369-3.865 US$/kg). MBA-bead can serve as an excellent adsorbent for removing Cu2+ ions from water.

Removal of phosphate from synthetic wastewater: A comparative study between both activated clays using an experimental design methodology.

Phosphate-loaded industrial wastewaters have resulted in numerous environmental issues that have hard hit the Gulf of Gabes-Tunisia, making the environmental protection one of the most compelling priorities. Consequently, this study aimed first to compare the amounts of phosphate adsorbed by two types of Tunisian activated clays. The second goal was to assess and optimize the phosphate removal efficiency of these clays, using Box-Behnken design (BBD) under response surface methodology. Results showed that the highest adsorption amounts of 130.16 mg g-1 , 125.42 mg g-1 were yielded for Jebel Haidoudi clay and Douiret clay, respectively. These values demanded an initial phosphate concentration of 300 mg L-1 , a contact time of 5 h, and a pH of 2). Thus, kinetic and isotherm studies of phosphate elimination from synthetic solutions demonstrated that for both activated clays, the pseudo-second-order and Langmuir equation fitted very well the experimental data, respectively. These results indicate that phosphate adsorption might be mainly a chimisorption phenomenon and a monolayer process. All these findings confirmed that both activated clays could be considered as a competent, cost-effective, efficient and ecological alternative for the elimination of phosphate from industrial wastewaters. PRACTITIONER POINTS: Activated clay could be adopted as an efficient and cost-effective adsorbent. The optimum conditions were nominated as 300 mg L-1 of initial phosphate concentration, 5 h contact times and pH = 2. The probable uptake mechanism of phosphate followed predominantly the acid-base interaction and hydrogen bond.

Hydraulic conductivity study of compacted clay soils used as landfill liners for an acidic waste.

Three natural clayey soils from Tunisia were studied to assess their suitability for use as a liner for an acid waste disposal site. An investigation of the effect of the mineral composition and mechanical compaction on the hydraulic conductivity and fluoride and phosphate removal of three different soils is presented. The hydraulic conductivity of these three natural soils are 8.5 × 10(-10), 2.08 × 10(-9) and 6.8 × 10(-10)m/s for soil-1, soil-2 and soil-3, respectively. Soil specimens were compacted under various compaction strains in order to obtain three wet densities (1850, 1950 and 2050 kg/m(3)). In this condition, the hydraulic conductivity (k) was reduced with increasing density of sample for all soils. The test results of hydraulic conductivity at long-term (>200 days) using acidic waste solution (pH=2.7, charged with fluoride and phosphate ions) shows a decrease in k with time only for natural soil-1 and soil-2. However, the specimens of soil-2 compressed to the two highest densities (1950 and 2050 kg/m(3)) are cracked after 60 and 20 days, respectively, of hydraulic conductivity testing. This damage is the result of a continued increase in the internal stress due to the swelling and to the effect of aggressive wastewater. The analysis of anions shows that the retention of fluoride is higher compared to phosphate and soil-1 has the highest sorption capacity.

Removal of phosphate ions from aqueous solution using Tunisian clays minerals and synthetic zeolite.

Phosphate ions are usually considered to be responsible for the algal bloom in receiving water bodies and aesthetic problems in water. From the environmental point of view, the management of such contaminant and valuable resource is very important. The present work deals with the removal of phosphate ions from aqueous solutions using kaolinitic and smectic clay minerals and synthetic zeolite as adsorbent. The pH effect and adsorption kinetic were studied. It was found that phosphate could be efficiently removed at acidic pH (between 4 and 6) and the second order model of kinetics is more adopted for all samples. The isotherms of adsorption of phosphate ions by the two clays and the zeolite samples show that the zeolite has the highest rate of uptake (52.9 mg P/g). Equilibrium data were well fitted with Langmuir and Freundlich isotherm.