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Title: Biosorbents: The Ecofriendly Agents for Removal of Dyes
Authors: Hassan, Warda
Keywords: Physical Sciences
Issue Date: 2018
Publisher: Islamia University, Bahawalpur.
Abstract: The present work aims to study the sorption capacities, mechanisms and potential of economical, low cost and abundantly available biomaterials i.e. a desert plant, Khar (Haloxylon recurvum) stems (HRS) and an agricultural material cotton plant (Gossypium hirsutum) stems (CS) biomass in removing different hazardous dyes from their aqueous solutions. These two biosorbents were treated with different agents e.g. urea, nitric acid and phosphoric acid to enhance their sorption capacities to check the role of different functional groups present on the surface of biosorbents in the removal of dyes. The biosorbent materials were characterized by different physico–chemical techniques such as FTIR, scanning electron microscopy (SEM), thermal analysis elemental analysis, BET, surface area by methylene blue method, and potentiometric as well as conductometric titrations. The pH and pH at the point of zero charge (pHpzc) of the adsorbents were also determined. Some other textural properties of biomass such as moisture, ash and volatile contents and bulk density, porosity, particle size distribution and pH of untreated as well as treated biosorbents were also determined by using different techniques. FTIR studies revealed that the oxygen containing groups i.e. carboxylic, carbonyls, esters, nitro, phosphate groups were mainly responsible for the binding of dyes on the surface of biomass. SEM studies indicated the porous and rough structure of the biomass and the size of these pores as well as roughness of the surface of biomass also increased with modifications. Thermal studies indicated the thermal stability of biosorbents at high temperature which was the proof that these biosorbents can also be used at higher temperature ranges. BET and other surface area studies indicated that these properties enhanced on treatment of the biomass. The potentiometric studies indicated the presence Abstract of acidic groups on the surfaces of biomass that are responsible for the attachment of dyes on the surface of biosorbents. The influence of different parameters were also studied to determine the kinetic and equilibrium sorption capacity biomass by using batch process. These parameters include time of contact, effect of biosorbent dose, concentration, pH of dye solution as well as the temperature of the system and the particle sizes of the adsorbents. The sorption data obtained from the time of contact was used for the kinetic studies of sorption systems. Four different kinetic models i.e. Lagergren’s pseudo 1st order, Ho’s pseudo 2nd order, elovich, intraparticle diffusion and liquid film diffusion model were used to study the adsorption reaction and diffusion mechanism of dyes on different biosorbents. The pH effect studies of the sorption of dyes showed that all of the acidic dyes show maximum sorption capacities in acidic ranges and vice versa for basic dyes. The sorption data for the effect of concentration of dye solution was used for the isotherm modelling of the data. Four different sorption isotherms i.e. Langmuir, Freundlich, Temkin and Dubinin– Radushkevich isotherms were used for the determination sorption capacities of different biosorbents. Regression coefficient and chi square tests were used for the applicability of specific kinetic and isotherm model. It was observed that temperature had a great effect on the removal of dyes, in some of the dye sorption systems the removal of dye was exothermic whereas in other it was an endothermic process. The qe(cal) (mg/g) obtained from Lagregren’s pseudo 1st order and Ho’s pseudo 2nd order kinetic models and qmax (mol/g) obtained from Langmuir sorption isotherm were also compared with other, reported in literature. The results of the studies indicated that the locally and abundantly available plant waste materials have great potentials for the removal of hazardous dyes from their aqueous Abstract solutions. These developed biomaterials provided an alternatives solutions to make the water clean for life and to minimize the damages caused by these hazardous chemicals as industrial effluents.
Gov't Doc #: 23551
Appears in Collections:PhD Thesis of All Public / Private Sector Universities / DAIs.

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