In the present study, the nano-silver-doped flax fibers (NAgDFF) are prepared in two steps. In the first step, oxidation of the flax fibers is performed by potassium periodate to form dialdehyde cellulose (DAC) and the second step is the reduction of silver ions by DAC. A series of characterization techniques of the photocatalyst NAgDFF was carried out using scanning electron microscopy, Fourier transform infrared spectroscopy, N2 adsorption isotherm, thermogravimetric analysis and energy-dispersive X-ray spectroscopy. The dye degradation potential of NAgDFF for methylene blue (MB), crystal violet (CV) and brilliant green (BG) (individually or mixture) was investigated using batch and column tests. The degradation efficiency was studied under optimized conditions such as pH (5.0), dye initial concentrations (100 ppm for MB and BG, and 150 ppm for CV), contact time (3.0 h), photocatalyst NAgDFF dose (0.08 g) and temperature (25° C). The maximum degradation efficiency of NAgDFF for MB, CV and BG is 64.75, 94.98 and 63.87 (mg/g), respectively. The kinetic studies show that the experimental data match well with the pseudo-second-order kinetic model. Furthermore, equilibrium isotherm data were analyzed according to Langmuir, Freundlich and Dubinin–Radushkevich equations. The thermodynamic parameters for the adsorption processes of cationic dyes on the NAgDFF fibers were also calculated; the negative value of ΔG° indicated the spontaneous nature of sorption. NAgDFF fibers were successfully applied for photodegradation of the investigated cationic dyes from different samples. The study was extended to investigate the biological activity of newly synthesized NAgDFF against various microorganisms.

In the present study, flax fiber based semicarbazide biosorbent was prepared in two successive steps. In the first step, flax fibers were oxidized using potassium periodate (KIO4) to yield diadehyde cellulose (DAC). Dialdehyde cellulose was, then, refluxed with semicarbazide.HCl to produce the semicarbazide functionalized dialdehyde cellulose (DAC@SC). The prepared DAC@SC biosorbent was characterized using Brunauer, Emmett and Teller (BET) and N2 adsorption isotherm, point of zero charge (pHPZC), elemental analysis (C:H:N), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analyses. The DAC@SC biosorbent was applied for the removal of the hexavalent chromium (Cr(VI)) ions and the alizarin red S (ARS) anionic dye (individually and in mixture). Experimental variables such as temperature, pH, and concentrations were optimized in detail. The monolayer adsorption capacities from the Langmuir isotherm model were 97.4 mg/g and 18.84 for Cr(VI) and ARS, respectively. The adsorption kinetics of DAC@SC indicated that the adsorption process fit PSO kinetic model. The obtained negative values of ΔG and ΔH indicated that the adsorption of Cr(VI) and ARS onto DAC@SC is a spontaneous and exothermic process. The DAC@SC biocomposite was successfully applied for the removal of Cr(VI) and ARS from synthetic effluents and real wastewater samples with a recovery (R, %) more than 90%. The prepared DAC@SC was regenerated using 0.1 M K2CO3 eluent. The plausible adsorption mechanism of Cr(VI) and ARS onto the surface of DAC@SC biocomposite was elucidated.

This study aimed to create CTAB-modified bentonite organoclay (Bt@CTAB) by mixing the naturally occurring mineral bentonite (Bt) with the cationic surfactant cetyltrimethylammonium bromide (CTAB). Elemental analysis, N2 adsorption–desorption isotherm, scanning electron microscopy (SEM), FTIR spectroscopy, XRD, and thermogravimetric (TGA) analysis have been employed to analyze both the unmodified Bt and the Bt@CTAB organoclay. The dye sorption onto Bt@CTAB organoclay was investigated in the batch and column modes using aqueous solutions of anionic food dyes, viz., Sunset yellow FCF (E110), Azorubine (E122), and Ponceau 4R (E124) (individually or in a mixture). Experimental variables affecting the adsorption process, such as initial dye concentration, contact time, temperature, pH, and adsorbent dose, are evaluated. From the kinetic investigations, the adsorption of E110, E122, and E124 dyes well matched the pseudo-second-order kinetic model. E110 and E122 dyes adsorption onto Bt@CTAB attained equilibrium in 120 min while attained in 240 min for E124. The investigated food dyes were expected to achieve maximum adsorption efficiencies at concentration of 100 ppm of (E110 and E124) and 150 ppm of (E124), an adsorbent dosage of 0.4 gL−1, and an initial pH 5. In addition, Langmuir model best fits the sorption isotherm data, with the maximum adsorption capacity at 303 K being 238 mg/g, 248.75 mg/g, and 358.25 mg/g for E110, E122, and E124, respectively. The Bt@CTAB organoclay can be regenerated up to the 4th cycle successfully. The thermodynamic studies revealed the spontaneous and exothermic nature of the adsorption of these anionic dyes onto Bt@CTAB organoclay. The prepared cationic Bt@CTAB organoclay was successfully applied for the removal of E110, E122, and E124 from real water samples, synthetic effluents, and colored soft drinks with a recovery (R%) higher than 95%. The plausible adsorption mechanism of E110, E122, and E124 onto Bt@CTAB organoclay is proposed to be due to electrostatic interaction and hydrogen bond formation. Finally, the present study shows that Bt@CTAB organoclay may be employed efficiently and effectively to remove anionic food dyes from a wide range of real water and colored soft drinks.

No abstract

Newly synthesized ortho-amino thio-phenol modified flax fibers (OATP-MFF) were prepared in two subsequent steps; at first flax fiber was pretreated with potassium periodate. Then, the pretreated fibers were condensed with ortho-amino thio-phenol to form the modified flax fibers(OATP-MFF). The OATP-MFF were characterized by (FTIR) Fourier transform infrared spectra, SEM and energy-dispersive X-ray Spectroscopy (EDX). The newly synthesized OATP-MFF chelating fibers were utilized for selective separation of Cu(II) from aqueous solution by adsorption methodology. The effects of pH, the initial concentration of metal ions, the adsorbent dosage, the interfering ions and the contact time on the adsorption capacity of OATP-MFF chelating fibers were investigated. The maximum adsorption capacity of Cu(II) at the optimum conditions was 92 mg/g. The adsorption process fitted well the second-order model kinetic of. The chemical (adsorption) reaction is the ratelimiting step that was proved from the kinetic model.