اميد احمدي

In today’s world, increasing consumer demand for natural, healthy, and additive-free plant-based products has made improving the visual and physical quality of foods -particularly their clarity- one of the main priorities in the food industry. Among such products, plant syrups such as fig and grape syrup, despite their rich nutritional profile and health benefits, face turbidity challenges during extraction and processing stages. The presence of colloidal particles, polyphenols, pectins, and suspended solids contributes to turbidity, which reduces consumer acceptance and negatively affects shelf-life and product stability. To address this issue, biosorption using natural, cost-effective, and locally available bioadsorbents derived from agricultural wastes -such as orange, lemon, and tangerine peels- has gained attention as a sustainable and efficient method for removing pollutants from aqueous and plant-based solutions. Accordingly, this study investigates the use of bioadsorbents from orange, tangerine, and lemon peels to reduce turbidity in fig and grape syrups. To evaluate the structural properties and functional groups influencing the adsorption performance, advanced characterization techniques including FESEM, EDX, FTIR, and BET were employed. Results indicated that the orange peel bioadsorbent possessed a more porous structure, higher active surface area, more uniform morphology, and lower particle agglomeration compared to tangerine and lemon peels. The presence of key functional groups such as carbonyl, hydroxyl, ether, and phenolic groups, confirmed via FTIR, along with the higher specific surface area (10 m²/g) obtained from BET analysis, demonstrated the superior adsorption performance of orange peel. Based on the adsorption experiments, the turbidity removal efficiency in fig syrup using orange peel reached 65.5%, significantly higher than the efficiency observed in grape syrup (36.8%). This difference may be attributed to the distinct chemical composition and structure of turbidity-causing compounds in each syrup; the colloidal and polyphenolic content of fig syrup exhibits stronger interactions with the active sites of the bioadsorbent. Subsequent investigation of operational parameters -including adsorbent type, contact time, dosage, gelatin concentration, and solution pH- was conducted using a one-factor-at-a-time method. Under optimal conditions (60 minutes contact time, 0.2 g adsorbent dose, 0.009 g gelatin, and acidic pH), a maximum turbidity removal efficiency reached 70.4% for fig syrup. While gelatin acted as a natural coagulant and improved adsorption through enhanced interaction, excessive amounts of gelatin led to reverse turbidity formation due to aggregation of protein particles. The proposed biosorption method demonstrates potential for industrial clarification of transparent food products and offers a sustainable alternative to conventional chemical clarification techniques.

In today's world, where water scarcity and and drinking water supply have become major challenges, population growth and the penetration of pharmaceutical pollutants such as the widely used antibiotic tetracycline into surface and groundwater have exacerbated this problem. The presence of tetracycline in water resources is hazardous for humans and other living organisms due to the creation of antibiotic resistance in bacteria and its irreversibility. Furthermore, a large part of tetracycline is excreted after consumption by humans and other living organisms and ultimately enters surface and groundwater. Therefore, the removal of this pollutant from environmental water resources is of great importance. Accordingly, the utilization of adsorption method as an effective and low-cost technique and the clinoptilolite mineral adsorbent as a cheap and available adsorbent have been considered for the removal of tetracycline from wastewater. However, the use of raw clinoptilolite as a natural zeolite is associated with challenges due to the presence of structural impurities, limited adsorption capacity, lack of reproducibility, and difficulty in separation. Effective solutions have been proposed to overcome these challenges, including chemical treatment and the addition of magnetic ferrites to the clinoptilolite. Therefore, this study investigated the impact of chemical treatment methods (dealumination, desilication and ion exchange) to modify the structure and surface of clinoptilolite. It also evaluated the effect of calcination temperature on the magnetic properties and adsorption performance of magnesium ferrite, its addition to the treated clinoptilolite adsorbent with different weight percentages, and finally the influence of various operational parameters on the removal efficiency of tetracycline from aqueous solution. The obtained results showed that by performing chemical treatment on the clinoptilolite adsorbent, in addition to removing impurities from the adsorbent structure and solving the non- reproducibility problem, a more uniform and porous morphology was also created in the adsorbent. Furthermore, the results of the characterization analyses confirmed that the adsorbent's structure was preserved after the chemical treatments, with no structural degradation observed. Among the chemical treatment methods, the alkaline treatment increased the surface area, created a more homogeneous structure and better distribution of active sites in clinoptilolite, and ultimately improved its performance in removing the tetracycline contaminant. On the other hand, by examining the effect of calcination temperature on the magnetic properties of magnesium ferrite and its performance in removing tetracycline, it was found that magnesium ferrite calcined at 600℃ has suitable magnetic properties and favorable adsorption performance. Moreover, it was observed that incorporating 20 wt% magnesium ferrite on the alkali-washed clinoptilolite resulted in the highest removal efficiency and adsorption capacity compared to the other synthesized weight percentages. This is attributed to a more uniform distribution of magnesium ferrite on the clinoptilolite surface, the creation of a strong interaction between them, a higher surface area, and consequently, better accessibility of pollutant molecules to the active sites in this composite. The highest tetracycline removal efficiency by the selected adsorbent under optimal operating conditions (pH=5, tetracycline concentration 10 ppm and adsorbent dose 1 g/L) was 91.58% and its adsorption capacity was 9.158 mg/g. Evaluation of the adsorption isotherm and kinetic studies revealed that the experimental data were well-fitted by the Langmuir isotherm and pseudo-second-order kinetics. The results obtained from the thermodynamic evaluation of the tetracycline adsorption process showed that the adsorption was physical, exothermic and spontaneous. The results of the reusability tests showed that the selected adsorbent retained its performance over 5 cycles without any loss of adsorption capacity. This adsorbent also showed excellent performance in the simultaneous removal of two pharmaceutical contaminants tetracycline and ciprofloxacin and no significant decrease in the tetracycline removal efficiency was observed. These results substantially confirmed the high selectivity of the synthesized nanocomposite.

In recent years, green synthesis technologies of precious metals have been developed due to the production of stable nanoparticles, prevention of the formation of undesirable by-products, simplicity of the synthesis method, cost-effectiveness and time-saving. In the present study, apple tree leaves were used to synthesize green silver nanoparticles. Also, various methods including microwave, autoclave, ultrasound, bain-marie, ultraviolet lamp, direct heating and ambient temperature were investigated for the green synthesis of silver nanoparticles. Characterization of the synthesized compounds was carried out using FTIR, XRD, TEM, DLS and UV analyses. Also, in order to investigate the antimicrobial properties of the synthesized samples, antimicrobial tests were performed using Escherichia coli (gram-negative) and Staphylococcus aureus (gram-positive). The results of the present study indicate that silver nanoparticles were successfully synthesized in all the aforementioned methods. The results of DLS analysis showed that the average size of silver nanoparticles synthesized by the three methods of ultrasound, UV lamp and bain-marie were 87, 96 and 98 nm, respectively, with the lowest average size and the two methods of direct heating and microwave were almost 100 nm and had average particle sizes of 101 and 104 nm, respectively. Also, the highest solution stability was obtained for the samples synthesized by the ultrasonic and microwave methods. Also, TEM images clearly showed that the shape of the particles was small and spherical and in nanometer size in the range of 10 to 50 nm. Finally, the evaluation of the antimicrobial activity of different methods for synthesizing silver nanoparticles showed that the highest inhibition zone against the bacteria studied (18 ± 0.001 mm) was related to the silver nanoparticles obtained by the ultrasonic method.

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