Biosorption of Methylene Blue by Chemically Modifi ed Cellulose Waste

Citric acid modifi ed cellulose waste（CMCW） was prepared via esterifi cation and used as a low-cost biosorbent for the removal of methylene blue（MB） from aqueous solutions. The effects of biosorbent concentration, initial pH of MB solution, biosorption temperature, contact time, and initial MB concentration on the biosorption of MB were investigated using batch biosorption technique under static conditions. The experimental results showed that CMCW exhibited excellent biosorption characteristics for MB. The maximum biosorption capacity of MB was up to 214.5 mg/g at an adsorption temperature of 293 K. The removal rate of MB onto CMCW reached the maximum at pH〉4 and the biosorption reached an equilibrium at about 50 min. The kinetic data can be described well with the pseudo-second-order model and the isotherm data was found to fi t the Langmuir isotherm with a monolayer adsorption capacity of 211.42 mg/g. The biosorption appears to be controlled by chemisorption and may be involved in surface adsorption and pore diffusion during the whole biosorption process.

Sustainable synthesis of 5-hydroxymethylfurfural from waste cotton stalk catalyzed by solid superacid-SO4^2-/ZrO2

A sustainable process was explored for the preparation of 5-hydroxymethylfurfural(HMF) by catalytic degradation of the waste cotton stalk. Solid super-acid(SO_4^(2-)/ZrO_2) was used as an efficient catalyst for the degradation of cotton stalk. Both decomposition experiments and kinetic study were conducted for the exploration of degradation condition and kinetics mechanism. The optimized experimental conditions are reaction temperature 503 K, reaction time 75 min and dosage of catalyst 30%(mass fraction) based on the decomposition experiments, under which a maximum yield of 27.2% for HMF could be achieved. Kinetic study was then carried out in the presence of SO_4^(2-)/ZrO_2. The theoretical results indicate that the activation energies for reducing sugar and HMF with catalyst are 96.71 k J/mol, 84.21 kJ/mol in the presence of SO_4^(2-)/ZrO_2, and they are 105.96 k J/mol and 119.37 k J/mol in the absence of SO_4^(2-)/ZrO_2.

Superior Au-adsorption performance of aminothiourea-modified waste cellulosic biomass

Waste cellulosic biomass obtains various applications due to low-cost and eco-benign characteristics.A general strategy is proposed for waste cellulosic biomass to be modified with dialdehyde functional groups as intermediates through periodate partial oxidation.Finally,aminothiourea-modified waste cellulosic biomass can be prepared through Schiff reaction.Waste corn stalk,cotton and paper as typical precursors,were used to prepare cellulosic biomass,abbreviated as AT-S,AT-C and AT-P,respectively,and their adsorption behaviors of Au(III)from the hydrochloric acid medium were investigated.The pseudo-second kinetics equation as well as the Langmuir isotherm equation can be used to depict the adsorption process,and the maximum adsorption capacities of Au(III)are21.4,19.0and3.28mol/kg for AT-S,AT-C and AT-P at298K,respectively.The adsorption capacities of Au(III)on aminothiourea modified corn stalk(AT-S)is almost357times greater than that of raw corn stalk.To the best of our knowledge,AT-S has the highest adsorption capacity towards Au(III).AT-S also displays a superior separation selectivity towards Au(III)in the presence of Cu(II),Ni(II),Co(II),Pt(VI),Pd(II)and Rh(III).Furthermore,the characterization analysis of XRD,TG,SEM,TEM and FTIR confirms that AuCl4– has been reduced to elemental Au nanoparticles and deposit onto the surface of the biomass.It shows a prospect for waste corn stalk to be used to adsorb Au(III)from liquid phase and the possible fabrication of gold nanoparticles by a general adsorption process without any reductant.