No abstract

No abstract

Hexavalent chromium is a mutagen and carcinogen that is of significant concern in water and wastewater. In the present study, magnetite nanoparticles (n-Mag) were investigated as a potential remediation technology for the decontamination of Cr (VI)-contaminated wastewater. Synthesized n-Mag was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and BET-N2 technology. To screen and optimize the factors affecting Cr (VI) removal efficiency by synthesized nanoparticles, Plackett-Burman (PB) and Taguchi experimental designs were used respectively. The crystalline produced n-Mag was in the size range of 60-70 nm and had a specific surface area (SSA) of 31.55 m(2) g(-1). Results of PB design showed that the most significant factors affecting Cr (VI) removal efficiency were initial Cr (VI) concentration, pH, n-Mag dosage, and temperature. In a pH of 2, 20 mg L(-1) of Cr (VI) concentration, 4 g L(-1)of n-Mag, temperature of 40 °C, 220 rpm of shaking speed, and 60 min of contact time, the complete removal efficiency of Cr (VI) was achieved. Batch experiments revealed that the removal of Cr (VI) by n-Mag was consistent with pseudo-second order reaction kinetics. The competition from common coexisting ions such as NO₃(-), SO₄(2-), and Cl(-) were not considerable, unless in the higher concentration of SO₄(2-). These results indicated that the readily synthesized magnetite nanoparticles have promising applications for the removal of Cr (VI) from aqueous solution.

A greenhouse experiment was conducted to evaluate the effects regarding inoculation of exopolysaccharide (EPS)-producing bacterium, the extracted EPS and silicon nanoparticles on Solanum lycopersicum L. seeds under salinity stress, in a completely randomized factorial design with three replicates. The inoculated seeds with silicon nanoparticles (8 gr L -1 ), bacterial EPS (0.01 M), and 1 mL of bacterial suspension (1×10 8 CFU mL -1 ) were sown in pots and irrigated with water at different salinity levels (0.3, 2, 4, 6, and 8 dS m -1 ). Results showed that treatment application could enhance salinity tolerance of tomato seeds and improve plant growth so that combined treatments of EPS and silicon nanoparticles (S.E.N), bacteria and silicon nanoparticles (S.B.N), and EPS with silicon nanoparticles and bacteria (S.E.B.N) were the best treatments for plant growth and improvement regarding salinity levels. The mentioned treatments significantly (p<0.01) increased root and shoot fresh or dry weight in comparison to the control sample. In addition, treatments significantly (p<0.01) decreased proline content and antioxidant enzyme activities. Thus, it can be concluded that applied treatments are suitable for agricultural and environmental applications and bring about less damage caused by salinity stress.

This study investigated the possibility and efficiency of absorbing chromium (VI) (Cr [VI]) ions from the polluted solutions by employing the chemically modified adsorbents (alkali, biochar, and acid rice bran), focusing on the possible impacts of the solution’s pH values, adsorbent’s dosages, concentrations, and contact times. The colori-metric method was used for Cr determination by employing an ultraviolet/visible spectrophotometer. The scanning electron microscope and Fourier transform infrared spectroscopy were used to analyze the characteristics of the modified adsorbents. The findings indicated that the optimized acid, biochar, alkali, and unmodified rice bran removal efficiency for Cr (VI) were 94.50%, 94.27%, 88.60%, and 90.18%, respectively. The increase of adsorbent dosage up to 2 g/L led to a rise in removal effectiveness (82.06%). Furthermore, the highest removal efficiency was obtained (94%) at the pH of 2.0, the contact duration of 100 min, Cr (VI) concentration of 50 mg/L, and dosage of 2 g/L, which was statistically the optimal condition for the modified rice bran. The adsorption kinetics was agreeably suited to pseudo-second-order, whereas the Freundlich isotherm equation was also suitably expounded the study’s findings. The findings implied that the acid and biochar rice bran performed remarkably in the reme-diation of the wastewater compared with alkali rice bran for reuse for industrial, agricultural, and environmental purposes.

No abstract

Background & Objectives:Nickel toxicity and its bioaccumulation potential in organisms at high concentrations, the use of cost-effective and environmental friendly remediation methods is necessary for the removal of nickel from polluted water and wastewaters. Bacterial biofilm be able to remove heavy metals from aqueous solutions and accumulate them in their cell structure. Therefore, the purpose of this study was to evaluate the nickel removal efficiency by biofilms of Pseudomonas aeruginosa supported on clinoptilolite. Methods: In this study, a strain of Pseudomonas aeruginosa as a biofilm coating supported on clinoptilolite. To ensure the establishment of biofilms, scanning electron microscopy was used. The effect of concentration, pH, support medium dosage, temperature and contact time were evaluated in 5 levels, and finally, the results were assessed by adsorption isotherm models. Results: The findings indicated that the maximum removal efficiency by biofilms of Pseudomonas aeruginosa supported on clinoptilolite (99/47%) was achieved in optimal condition containing 900 mg. L -1 of nickel concentration, pH of 9, supporting medium dosage (clinoptilolite) 2.36 g. L -1 , temperature of 25 ° C and the contact time of 45 days. The fitness of data in Freundlich adsorption isotherm model revealed that the heterogeneity of adsorbent surface. Conclusion: This study indicates that the use of biofilm coating on the surface of clinoptilolite, can be a good candidate to remove the nickel from the aqueous media.

No abstract