Intensive industrial and urban growth has led to the release of increasing amounts of environmental pollutants. Contamination by metals, in particular, deserves special attention due to their toxicity and potential to bioaccumulate via the food chain. Conventional techniques for the removal of toxic metals, radionuclides and precious metals from wastewater all have a number of drawbacks, such as incomplete metal extraction, high cost and risk of generating hazardous by‐products. Biosorption is a cost‐effective and environment‐friendly technology, an alternative to conventional wastewater treatment methods. Biosorption is a metabolically independent process, in which dead microbial biomass is capable of removal and concentrating metal ions from aqueous solutions. Free microbial biosorbents are of small size and low density, insufficient mechanical stability and low elasticity, which causes problems with metal ion desorption, separation of the sorbent from the medium and its regeneration. Hence, the possibilities for the implementation of continuous biosorbent processes for metal removal in flow‐type reactor systems are reduced and the practical application of biosorption in industrial conditions is limited. By immobilizing microbial biomass on suitable carriers the disadvantages of free biosorbents are eliminated and more opportunities for practical use of biosorption become available. This review examines different immobilization techniques and carriers, certain basic features and possibilities of using immobilized microbial biosorbents for the removal and concentration of metals from aqueous solutions.
Biosorption of Pb(II) ions from a model solution was investigated using Streptomyces fradiae biomass as biosorbent pretreated with sodium hydroxide. The mycelium is a waste product from the biotechnological production of the macrolide antibiotic tylosin in the pharmaceutical industry. The biosorption study was conducted in a batch system with respect to initial pH, initial metal concentration and contact time. For a description of the biosorption equilibrium, Langmuir and Freundlich adsorption models were used. Equilibrium data fitted better to the Langmuir model and the calculated maximum biosorption capacity was 138.88 mg¢g ¡1 at initial pH 5.0, contact time of 120 min, biosorbent dose of 1 g¢dm ¡3and concentration range for the Pb(II) ions from 10 to 200 mg¢dm ¡3 . Pseudo-first and pseudo-second order kinetic models were applied to the experimental data. The results indicated that the Pb(II) uptake process followed the Ho equation. The interference of co-present ions Cu(II) and Zn(II) on the Pb(II) biosorption was also studied. It was determined that at the highest Pb(II) concentration (200 mg¢dm ¡3 ) Cu(II) and Zn(II) caused 27.22% and 24.88% decreasing in Pb(II) uptake, respectively. The obtained results could be useful in prospective applications of chemically modified waste mycelium of S. fradiae as an alternative biosorbent for Pb(II) removal from aqueous solutions.
Waste biomass from Bacillus cereus immobilized in sodium alginate and co-immobilized with activated carbon or with bentonite into alginate gel was studied for Pb(II), Cd(II) and Hg(II) removal from aqueous solutions. The composite biosorbent consisting of waste B. cereus biomass co-immobilized with activated carbon into alginate beads was selected as the most prospective for heavy metals removal. Immobilization increased both the removal capacity and the mechanical strength of the biosorbent. Major process parameters were optimized and maximum removal efficiency of 92.13% was reached for Pb(II) ions at pH 5.0, biosorbent dosage 2 g/L, temperature 25 C, agitation speed 120 rpm for 120 min.
Pretreated waste Streptomyces fradiae biomass was utilized as an eco-friendly sorbent for Congo Red (CR) and Methylene Blue (MB) removal from aqueous solutions. The biosorbent was characterized by Fourier transform infrared spectroscopy. Batch experiments were conducted to study the effect of pH, biosorbent dosage, initial concentration of adsorbates, contact time and temperature on the biosorption of the two dyes. The equilibrium adsorption data were analysed using Freundlich and Langmuir models. Both models fitted well the experimental data. The maximum biosorption capacity of the pretreated Streptomyces fradiae biomass was 46.64 mg g-1 for CR and 59.63 mg g-1 for MB, at a pH 6.0, with the contact time of 120 min, the biosorbent dosage of 2 g dm-3 and the temperature of 298 K. Lagergren and Ho kinetic models were used to analyse the kinetic data obtained from different batch experiments. The biosorption of both dyes followed better the pseudo-second order kinetic model. The calculated values for ΔG, ΔS, and ΔH indicated that the biosorption of CR and MB onto the waste pretreated biomass was feasible, spontaneous, and exothermic in the selected temperature range and conditions.
Betonica bulgarica is an endemic species distributed in Bulgaria. The chemical composition of the essential oil analysed by GC–MS (Gas chromatography–mass spectrometry) and the content of trace elements analysed by ICP–MS (Inductively coupled plasma mass spectrometry) were determined. Additionally, a study on the types and distribution of trichomes was done using a microscope with a camera. The essential oil was characterized using a high concentration of sesquiterpene hydrocarbons, whose major compounds are β-caryophyllene (17.4%), germacrene D (9.9%), and β-bourbonene (6.7%). The contents of manganese (177.2 µg/g) and strontium (156.8 µg/g) were highest among the investigated micronutrients. Two types of trichomes were identified on the adaxial and abaxial epidermises of the leaves of B. bulgarica—covering and glandular. Peltate stacked glandular trichomes with a four-celled head of type B were observed on the leaf surface.
Four azo dyes known to form anionic complexes with V(V) were investigated as potential liquid–liquid extraction–spectrophotometric reagents for the antihistamine medication hydroxyzine hydrochloride (HZH). A stable ion-association complex suitable for analytical purposes was obtained with 6-hexyl-4-(2-thiazolylazo)resorcinol (HTAR). The molar absorption coefficient, limit of detection, linear working range, and relative standard deviation in the analysis of real pharmaceutical samples (tablets and syrup) were 3.50 × 104 L mol−1 cm−1, 0.13 μg mL−1, 0.43–12.2 μg mL−1, and ≤2.7%, respectively. After elucidating the molar ratio in the extracted ion-association complex (HZH:V = 1:1), the ground-state equilibrium geometries of the two constituent ions—HZH+ and [VO2(HTAR)]−—were optimized at the B3LYP level of theory using 6-311++G** basis functions. The cation and anion were then paired in four different ways to find the most likely structure of the extracted species. In the lowest-energy structure, the VO2 group interacts predominantly with the heterochain of the cation. A hydrogen bond is present (V–O···H–O; 1.714 Å) involving the terminal oxygen of this chain.
Ginkgo biloba has been cultivated in Bulgaria since the end of the 19th century. Ividual specimens can be seen in almost every park. Females of the tree are considered contaminants of the landscape because their ripe seeds have a strong odor and are not utilized. We undertook this study to clarify whether ginkgo seeds of local origin can be converted from an unwanted and unused environmental pollutant into a source of beneficial compounds. Various analytical and chromatographic methods were used to quantify the major constituents and ten biologically active compounds in methanol seed extract. The results showed that the seeds are low in proteins (5%) and fats (1%); the seeds were also rich in unsaturated fatty acids and tocopherols. About 44% of nut starch was resistant to in vitro enzymatic hydrolysis. The amount of terpene trilactones in an aqueous-methanol seed extract was significantly higher than the number of flavonoids. Ginkgotoxin and ginkgolic acid were also found. The extract demonstrated weak antimicrobial activity against thirteen microorganisms. This study revealed that seeds of locally grown Ginkgo trees can be used as a source of biologically active substances. The chemical composition show similarity to those of seeds from other geographical areas.
Introduction: Selenium (Se) is one of the environmental factors with an essential role in the pathogenesis of autoimmune thyroid disease (ATD). Scarce data is available for the selenium status of the Bulgarian population especially for patients with thyroid disorders. Aim: To compare the serum selenium (s-Se) concentrations in patients with ATD and healthy controls from Bulgarian population. Materials and methods: The s-Se concentrations were measured in 105 patients newly diagnosed or untreated for the previous 6 months with ATD (mean age 44±13 years). The patients were divided into three groups: euthyroid autoimmune thyroiditis (AIT) (n=31), hypothyroid AIT (n=33), and hyperthyroid patients with AIT or Graves’ disease (GD) (n=41). The results were compared to s-Se concentrations in 40 age- and sex-matched healthy controls. Determination of s-Se was carried out by inductively coupled plasma mass spectrometry (ICP-MS) after microwave-assisted acid mineralization of the serum samples. Results: The s-Se concentrations in patients with hyperthyroidism were significantly lower than those in the control group (hyperthyroidism: 69±15.0 µg/L vs. controls: 84±13 µg/L, p<0.001). There was no significant difference in the s-Se concentrations between euthyroid and hypothyroid participants with AIT and healthy controls. The s-Se concentrations in our control individuals were within the range of 53-137 µg/L, reported in literature data on mean serum and plasma levels of European healthy adults. Conclusions: The mean s-Se concentrations observed in all groups were below or close to the cutoff value of 80 µg/L, considered optimal for the activity of the Se-dependent antioxidant systems.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.