Thermo-Chemical Modification of Cellulose for the Adsorptive Removal of Titan Yellow from Wastewater

This research work focuses on the isolation and thermo-chemical modification of cellulose and its application as an adsorbent for the removal of organic pollutants. The used cellulose was collected from a locally available plant (Olive Europa) commonly called Zaitoon. The stem branches of Zaitoon were collected and then kept in water for 40-45 days at room temperature to extract the cellulose fibers. These cellulose fibers were then kept in the Soxhlet apparatus for washing in n-hexane for 72 h. The purified cellulose was divided into three parts: one part was subjected to thermal activation (TAC), the second was modified chemically (CMC) with Benzyl Chloride, while the last one remained un-functionalized (UFC). All the three forms of cellulose were characterized via FTIR and SEM, then utilized for the removal of Titan Yellow (TY) dye from aqueous media via adsorption process by varying the contact time, temperature, concentration of dye and type, and dose of adsorbent. The adsorption efficiencies of all adsorbents were compared under different experimental variables. Thermally activated cellulose showed the best results for the removal of TY compared with other materials. The calculated removal percentage of TY was found to be 97.69, 94.83, 94.83, and 98% under equilibrium conditions of contact time, temperature, adsorbent dose, and TY concentration. Similarly, the uptake capacities of TAC under optimal experimental conditions were found to be 19.56, 18.96, 18.52, and 18.75 mg/g. Thermodynamic studies of TAC, CMC, and UFC showed that the values of ΔG are negative, while those of ΔH and ΔS are positive in all cases and at all temperatures. This indicates that the TY elimination process is endothermic and spontaneous with an entropy-driven nature. The obtained results indicate that the as-fabricated low-cost biomaterials can effectively remove dyes from wastewater through physicochemical interactions. The removal process was influenced by the nature of the adsorbent and the operating variables.

Kinetics, Thermodynamics, and Isotherms of Methylene Blue Adsorption Study onto Cassava Stem Activated Carbon

Water treatment using activated carbon is widely accepted, despite its high production cost. Therefore, this study was aimed to investigate the potential of cassava stem in activated carbon form for methylene blue (MB) dye uptake from water. Raw cassava stem (RCS) was also utilized to evaluate the difference between cassava stem in its raw form and after being converted to the activated carbon (ACS). The MB adsorption from water using the RCS and ACS was done in this study. The batch adsorption study showed fast MB uptake by ACS at 60 min contact time, while higher adsorbent dosage and higher pH contributed to higher adsorption percentage. The thermodynamic study showed positive values of ∆H° of ACS, indicating that the adsorption process of MB was endothermic. Meanwhile, the negative value of ∆G° showed that the adsorption processes of MB were spontaneous. The thermodynamic study showed higher fitting to Langmuir isotherm, with data from the kinetic study showing better pseudo-second-order equation fitting, which suggests the chemisorption process had happened. The highest adsorption recorded by ACS was 384.61 mg/g, indicating the possibility of cassava stem as the lower cost raw material for activated carbon production with excellent adsorption characteristics.

Physicochemical and instrumental characterization of rice husk and its potential use as a low cost adsorbent for mutagenic dye bromophenol blue

In this study fine powder of rice husk were used as novel adsorbent for the removal of bromophenol dye. Different conventional physicochemical analysis and instrumental techniques were used to characterize the adsorbent. The surface area of the adsorbent was found to be 160.6 m2/g with bulk density of 1.139 g/dm3. Proximate and ultimate analysis showed that the selected material is a rich source of carbon with the advantage of not having Sulphur contents. FTIR and SEM analysis confirmed the surface modification via aqua regia in comparison to parental material (that have enhanced its surface porosity). The maximum uptake capacity (0.8 mg/g) of dye was reached at pH 3, 20 ppm of adsorbate concentration, and 0.5 g of treated rice husk dosage at room temperature and 60 min of equilibrium time. The equilibrium adsorption data was best explained by Freundlich adsorption isotherm with R 2 value of 0.998. Kinetic studies revealed that adsorption follows pseudo second order kinetic model with R 2 value of 0.997, K 2 equal to 0.831 (g/mg min), and q e value of 0.97 mg/g. The thermodynamic parameters (∆S° = 6.78 J/mol, ∆H° = 1501 J/mol, ∆G° −1.50, 0.5, 0.621 and 0.0787 kJ/mol corresponding to 293, 303, 313 and 333 K) pointed towards the endothermic and spontaneous nature of the process.