SOUTHERN JOURNAL OF SCIENCES

Background: Industrial wastewater contains pollutants that are detrimental to human health in varied proportions. Among the pollutants are heavy metals, including Zn2+, Pb2+, and Cu2+ found in a characterized pharmaceutical wastewater. Several techniques have been proposed for the heavy metal sequester. However, they are with attendant challenges. The adsorption techniques using clay-metal oxide modified adsorbent/composite such as silver-clay adsorbent is considered suitable for an effective sequestering process. Aims: To develop and characterize Ag/clay adsorbent for pharmaceutical wastewater treatment. Methods: The Ag nanoparticles were synthesized using Parkia biglobossa aqueous leaves extract in an optimization study. The raw clay was beneficiated and doped with silver nanoparticles via the wet impregnation method. The silver-clay adsorbent was characterized using FTIR, XRD, SEM, and EDS characterization tools. The developed adsorbent was used for the batch adsorption process of the heavy metal ion removal from the wastewater. Results and Discussion: The phytochemical analysis and FTIR results of the P. biglobosa showed that the leaf contains phenol, tannin, and flavonoids which acts as reducing, capping, and stabilizing agent required for synthesizing the silver nanoparticles. The prepared silver nanoparticles modified clay adsorbent Ag/clay, have evenly distributed stacks of pseudo-hexagonal plates, are rich in silica, possess silver nanoparticles in the frameworks, and contain functional groups suitable for binding heavy metals. The adsorptions of Zn2+, Pb2+, and Cu2+ from pharmaceutical wastewater onto the silver-modified clay were studied as a function of adsorbent dosage and contact time. The percentage removal results obtained showed that the adsorbent had up to 99.96%, 99.5%, and 99.44% removal efficiency for Zn2+, Pb2+, and Cu2+, respectively, which are better compared with previous studies. The adsorption process was feasible, spontaneous, and exothermic, with Langmuir and Pseudo-second-order models as best fits for the process. Conclusions: The adsorption of selected heavy metal ions onto the green synthesized silver-modified clay adsorbent (Ag/clay) was feasible, spontaneous, and exothermic in the order Zn2+>Pb2+>Cu2+ with Langmuir and Pseudo-second-order model best fitted for the process. These show that the synthesized silver oxide nanoparticles supported on local clay can be used as a potentially low-cost adsorbent to remove heavy metal ions from industrial wastewater.

Sugar beet is a crop able to resist high levels of soil salinity after emergence and establishment. Considering the significant difference in the effect of nitrogen forms on sugar beet performance under normal conditions, the form of nitrogen may affect the performance of sugar beet plants under abiotic stress, particularly salinity. Additionally, exploring the most appropriate type of nitrogen for sugar beet could mean optimizing sucrose content. Therefore, here using two lines, sugar beet was grown in pots (filled with 4 kg soil), salt-resistance (line 7233- p.29 x Mst), and salt-sensitive (line 3929-21939), the effect of two different forms of nitrate in the form of calcium nitrate (1 g per pot) and ammonium in the form of ammonium sulfate (1 g per pot) under normal and salt stress condition (40 Millimoles per liter sodium chloride) were evaluated. The result revealed the positive influence of nitrate over ammonium by indicating higher dry weight in both sensitive line: 19.2 and 13.6 g, and tolerance line: 20.4 and 13.6 g, respectively alone and in combination with salinity stress. Similarly, root yield levels positively influenced by nitrate treatment either alone or under salinity stress (sensitive line: 194.5 and 243.2 g and tolerance line: 207 and 249.5 g). The outcomes additionally showed the accumulation of proline aerial parts in both lines, and however, the proline accumulation of sensitive line was higher (3.9 mg/g dry weight). Moreover, induction of proline aggregation was considerably higher in nitrate nitrogen-treated sensitive line (9.3 mg/g dry weight). The absence of significant difference was obseved between nitrogen treatments in terms of extractable sucrose and root molasses sugar. Also, the root impurities increased in those treated with nitrate-nitrogen and salinity. It can be concluded that nitrate-nitrogen has improved the performance of both sugar beet lines against salinity stress, and its practical application is adviseable.

Today, salinity stress causes extensive damage to crops, and high soil salinity is one of the limiting factors for crop yields. A practical approach to lessen the negative effect of salinity stress is to use mineral nutrition methods such as spraying plants with silicone. To investigate and compare the effect of silicon and silicon nano-chelate on the wheat plant resistance (Shiroodi cultivar) to salinity stress, a factorial experiment was designed and conducted in a completely randomized design with five replications under hydroponic conditions. Experimental treatments included concentrations of 0 and 2 mmol/L silicon, 0 and 0.424 g/L silicon nano-chelate, 0 and 150 mmol/L sodium chloride, and their interaction. The growth and physiological indices showed that salinity stress decreasing effect on shoot dry weight, root fresh weight, catalase activity, and ascorbate peroxidase. These increases indicate the activation of the plant defense system against salinity stress conditions. The results also showed that silicon nano-chelate treatment under salinity stress reduced dry and fresh weights of roots and shoots. These two compounds additionally influenced the content of catalase activity, ascorbate peroxidase, and superoxide dismutase content in shoots. Simultaneously, the silicon and silicon nano-chelate treatment under salinity stress reduced the dry and fresh weight of roots and shoots, catalase activity, and ascorbate peroxidase. Therefore, the results obtained in this study generally showed that silicon under salinity stress increased plant growth and positively affected the activity of its antioxidant system. But silicon nano-chelate not only did not improve plant performance but also reduced its growth.