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.

Carbohydrazides functionalized cellulose (CH-MC) was prepared and characterized using some qualified techniques such as Scanning Electron Microscopy (SEM), Infra-Red (FT-IR), Elemental analysis (EA) and Thermogravimetric analysis (TGA). The prepared CH-MC was employed for uptake of heavy metal ions such as, Hg 2+ and Cu 2+ from different samples. Sorption parameters: such as pH, temperature, time of sorption and the concentration of sorbent were investigated to determine the best conditions for sorption. The kinetic of sorption agreed with the second-order model and the chemical adsorption is the rate-limiting step. In addition, the sorption isotherm experiments revealed that the best adequate with Langmuir model which the maximum adsorption capacities for Cu 2+ and Hg 2+ metal ions on CH-MC are 43.3, 64 mg/g, respectively. The real samples including Hg 2+ and Cu 2+ were used for analytical applications on the present methodology and the observed data is promising.