Preparation Of Activated Carbon And MXene And Its Studies On The Adsorption Properties Of Dyes

Textile dyes are the most common cause of water pollution,posing serious threat both to aquatic and terrestrial beings.To deal with this issue,adsorption approach remains the most promising and economical method.However,development of adsorbent material with high adsorption capability at minimum expense remains a challenge to overcome.Here,we report development of new adsorbent materials with excellent dye adsorption capability.The materials include popcorn-derived activated carbon(PDAC)and new two-dimensional material Ti2CTx known as MXene.The two materials were investigated in detail for their morphological and dye adsorption characteristics.The adsorption kinetics and thermodynamics of the designed experiments was also evaluated.The main outcomes are as follows:1.Preparation of popcorn-derived activated carbon(PDAC)and its adsorption properties on organic dyesHere,corn kernels were taken as the carbon source,where radiation effect of the microwave oven resulted in formation of fluffy popcorn derived activated carbon material.To achieve the best activated carbon,PDAC was prepared with different alkali/char ratios(3:1/4:1/5:1)using carbonization activation process.The elaborate characterization studies of the optimized PDAC showed that the prepared material possess ultra-high specific surface area(>3000 m2·g-1),well-developed hierarchical pore structure and abundant surface functional groups.The adsorption capability of PDAC was evaluated against four common dyes i.e.rhodamine B(RhB),congo red(CR),methylene blue(MB)and methyl orange(MO).Among the various PDAC produced,the PD AC-4(alkali:char=4:1)which was determined to possess greatest specific surface area and abundant active sites showed the highest adsorption capability(7765 mg·g-1)for RhB dye.The adsorption model was determined to follow pseudo-second order kinetic where adsorption was evaluated to be consistent with Langmuir's monolayer adsorption.The adsorption process,which was spontaneous,endothermic and met the quasi-secondary kinetic model was mainly controlled by physical adsorption(pore adsorption and surface adsorption).The PDAC,when tested for mixture of dyes(RhB+MB,RhB+MB+MO),exhibited excellent decolorization ability with maintained adsorption capacity of>3000 mg·g-1 after three cycles of dye adsorption-desorption with an initial concentration of 1000 mg·L-1.2.Preparation of MXene(Ti2CTx)and its adsorption properties on organic dyes.The two-dimensional MXene(Ti2CTx)nanosheets were prepared using acid etching method where Ti2AlC was etched with LiF and HC1 instead of conventional HF.The obtained MXene sheets were determined to be very thin 2D nanosheets with abundant surface-active functional groups(-OH,=O,-F).The Ti2CTx was then tested for its adsorption characteristics against RhB where efficient adsorption of 2439 mg·g-1 was achieved with initial concentration of 1000 mg·L-1 and adsorption equilibrium time of 1 min.The adsorption reaction was determined to follow pseudo-second order kinetic model where the Freundlich isotherm model accurately described the adsorption to be multi-layer process.The thermodynamics determined the adsorption process to be spontaneous and exothermic.The adsorption of RhB over Ti2CTx nanosheets could be attributed to the synergic combination of chemical effects(ion exchange)and physical effects(electrostatic interaction,hydrogen bonding,and van der Waals force).Moreover,the pH and salt ion concentration were noted to have little effect on the adsorption of RhB.Thus,we can speculate that the Ti2CTx can maintain a stable adsorption performance for RhB even under complex environment conditions.