Study On Adsorption Of P-chlorophenol From Solution By Organic Modified Bentonite

Bentonite, widely present in nature, is a kind of nonmetallic layered clay mineral.After organically modified bentonite, the layer spacing, hydrophobicity and surfacestructure was improved well, and which is widely used in the field of environmentalpollution control. In this paper, bentonite ore produced in Xinyang, Henan waspurified and sodium pillared, and cetyl trimethyl ammonium bromide (CTAB) as theorganic intercalation agent was used to prepare organic modified bentonite, referredOr-NaBt, and studied its effect on p-chlorophenol of simulated wastewater adsorptionbehavior.The means of X-ray diffraction, scanning electron microscopy, determination ofspecific surface area and Fourier transform infrared spectroscopy are used tocharacterize the structural properties of bentonite samples. The results showed that thecationic modifier CTAB had fully intercalated into interlayer of bentonite, whichmade the layer spacing increase, and more enhanced hydrophobic; meanwhile CTABmolecules interacted with bentonite crystals, the inner and outer surface of bentonitewas organic, and adsorption reactive groups increased accordingly; the isoelectricpoint of bentonite ore and Or-NaBt were11.83and7.22respectively, and Or-NaBtsurface electronegativity weakened correspondingly.Or-NaBt adsorption of p-chlorophenol in water experimental studies showed thatadsorption in the same condition, compared to bentonite ore, Or-Bt, powderedactivated carbon and Or-NaBt on adsorption properties, Or-NaBt adsorption capacityof p-chlorophenol was the strongest; pH value played greater impact on the adsorptionprocess, removal rate of p-chlorophenol increased with pH value increased and thendecreased, at pH=7of adsorption effect was the best, in the initial concentration of50mg/L, pH value of7, temperature of25℃, shaking speed of180r/min for factorcondition, Or-NaBt adsorption of p-chlorophenol equilibrium reached at2h, theremoval rate was up to92.37%; adsorption properties of Or-NaBt mainly reflect as thedual role of surface adsorption and interlayer organic phase hydrophobic anchoring.Regeneration effect of Or-NaBt after adsorption is proportional to the concentration ofregeneration agent NaOH, using0.2mol/L of NaOH to regenerate Or-NaBt, theremoval rate of Or-NaBt adsorption of p-chlorophenol reached80.75%, Or-NaBtregenerated after four times still has a certain adsorption capacity, Or-NaBt was regenerated by the alkali whose active adsorption sites get better recovery, so theprepared Or-NaBt has good recyclability.Adsorbent Or-NaBt adsorption of p-chlorophenol followed the pseudo secondorder kinetics equation, Obtained the theoretical adsorption value qeby fitting and theactual adsorption value qe*were basic consistent, the adsorption activation energywas15.50kJ/mol, and adsorption reaction belonged to chemical adsorption type.Freundlich isotherm adsorption equation could better describe Or-NaBt adsorptionbehavior of p-chlorophenol, and which showed that adsorbent surface was nothomogeneous, and between the various active adsorption sites existed interaction;enthalpies ΔH and Gibbs free energy ΔG value in adsorption process system were lessthan zero, which indicated that Or-NaBt adsorption of p-chlorophenol wasspontaneous exothermic reaction, meanwhile the absolute value of ΔG increased asrising of reaction temperature, the corresponding adsorption driving force alsoincreased, that temperature elevated could increase the rate of adsorption.