U TILIZATION of electrospinning technique accompanied by chemical modification as well as, the production of low-cost adsorbent based on polyamide nanofibers is the aim of our current work. The electrospinning parameters (polymer conc, applied voltage, and collector distance) have been studied. The obtained polyamide nanofiber mats were modified with citric acid at various conditions (concentration, temperature and catalyst concentration). The optimum conditions of this modification were investigated by MB uptake efficiency. The obtained data illustrate a positive relationship between citric acid concentration and MB uptake using the modified polyamide nanofiber. The produced adsorbent was well characterized using SEM, ATR-FTIR, and surface area measurement. Scanning Electron Microscopy clarifies minor swelling of nanofibers during the modification process which attributed to the increase in fiber diameter and therefore reduction in the fiber surface area. The adsorption performance of the nanofiber mat was assessed as a function of pH, nanofiber mat dosage, contact time, and initial dye concentration. Kinetics and isotherms analysis were investigated as well. The MB separation capability of the modified PA-nanofiber was considerably higher than that of the PAnanofiber. The kinetic data of both nanofiber mat was better fitted with the pseudo-second-order model. Also, the equilibrium data of PA-nanofiber was better fitted with Freundlich model and Langmuir model in case of the modified PA-nanofiber. The adsorption behavior was favorable chemisorption process as inferred from the kinetics, and the isotherms studies. The results of this study promote the modified PA-nanofiber as a potential adsorption filters for dyeing wastewater decolourization.

Hexavalent chromium Cr (VI) is a toxic heavy metal that discharged by many industries into the water streams. It is the most toxic form of chromium compound, which causes significant damage to receiving ecosystems. A microalgal species, Chlorella sp., was used as a biosorbent material to remove Cr (VI) from Cr-contaminated effluents. Furthermore, different variables: pH, temperature, contact time, Cr (VI) concentration and algal dose, were optimized in order to determine the optimum conditions that achieve the highest removal efficiency. The optimization process was achieved through two steps: one factor at a time (OFAT) experiments followed by 25 general full factorial. Moreover, molecular identification was performed using 18S rRNA in order to demonstrate the species of Chlorella, and it was identified as Chlorella sorokiniana. The highest chromium removal efficiency of 99.6793% was achieved at 100 ppm Cr (VI) after three days' contact time. Chlorophyll ‘a’ estimation as a growth indicator stated that Chlorella sorokiniana can tolerate 100 ppm Cr (VI) for three days' exposure. The results suggested that Chlorella sorokiniana is a good biosorbent material and it distinguished by its high ability to uptake Cr (VI) from solutions.

T HE INFLUENCE of different ratios of fillers addition such as limestone and micro white sand, as well as nano-titania particles on the physico-mechanical properties of ordinary white Portland limestone cement (OWPC), has been studied. One mix (10.00 wt. %) of equal ratios from limestone and white sand in micro scale, partially replaced by cement clinker. Mechanical strength, phase composition, and microstructure of blended cement have been investigated. The results showed that filler reduces the setting time and total porosity, improve the strength, free lime content, combined water content and bulk density of cement pastes due to the pozzolanic effect of micro white sand that replaces clinker and enhance an excess amount of hydration products. It can be concluded that limestone fills the pores between cement particles due to the formation of carboaluminate, while micro sand increases the hydration C-S-H product. TiO 2 nanoparticles (i.e., less than 100 nm) shows a great efficiency in enhancing the mechanical strength of cement paste due to the efficient incorporation of nanoparticles as active sites for gel Tobermorite C-S-H fibers growth during hydration,

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