Study On Modification Of Chinese Water Chestnut As Dye And Metal Adsorbents

In this paper, the extractions of dietary fiber and cellulose from Chinese water chesrnutpeel dregs were studied. The contents of the cellulose was measured via Neutral detergentmethod; and the dietary fiber was extracted by alkali, and the optimal conditions wasdetermined via orthogonal experiments.The optimal condition of dietary fiber extraction is7%NaOH concentration at70℃, theratio of solid-liquid as1:15, reached62.5g （100g）^-1; The water holding capacity, theexpansive force and the capacity of absorbing oil was determined as5.077±0.216g g^-1,5.17±0.20mL g^-1and0.82±0.03g g^-1respectively. The optimal processing conditions forcellulose extraction were treated by22.5%NaOH concentration, at70℃for0.75h,70℃ofacid solution. The recovery was32.25%, with purity88.32%.Pretreated Chinese water chestnut peel fiber was modified through etherification andamoination, as adsorbents of dyes and the adsorption conditions of modified Chinese waterchestnut peel fiber （MWCP） were studied under different factors to research the adsorptionmechanism and adsorption kinetics.The results showed that the adsorption effect of modified products with dye waste wassignificant, at the concentration of100mg L^-1, and the optimum50℃, pH2-8, the removalrate was about100%for Direct Red4B, Vat Yellow G and Reactive Dark Blue B respectively.The adsorptive capacity of the modified Chinese water chestnut peel fiber on Reactive DarkBlue B, Direct Red4B and Vat Yellow G reached about280mg g^-1,280mg g^-1,200mg g^-1,respectively.The adsorption behaviors of the modificated the modified Chinese water chestnut peelfiber for Direct Red4B, Vat Yellow G and Reactive Dark Blue B were found to follow theLagrange pseudo-second kinetics model a. Meanwhile, adsorption process followed Langmuirisotherm model better. FT-IR and SEM analysis indicated that the etherification andamination reactions took place on the surface of Chinese water chestnut fiber.Chinese water chestnut peel dreg was also modificated as metal adsorbent with succinicanhydride in pyridine. The the modified Chinese water chestnut peel dreg exhibited high Cu²⁺,Cd²⁺and Pb²⁺adsorption capacity. FT-IR analysis indicated that the carboxylation reaction took place during the modification of the Chinese water chestnut peel. The Cu²⁺, Cd²⁺andPb²⁺adsorptions of the modified Chinese water chestnut peel dreg were found to depend onthe initial metal concentration, adsorption time and pH value. The maximum adsorptioncapacities of modified peel dreg of the Chinese water chestnut peel dreg reached44.80±2.68mg g^-1for Cu²⁺at pH5.5,80.73±6.25mg g^-1for Pb²⁺at pH5.6and45.94±3.15mg g^-1forCd²⁺at pH7.8respectively. The adsorption of the modified Chinese water chestnut peel dregfor the three metal ions was found to followed the Pseudo second-order kinetics model andthe experimental data coincided well with Langmuir model.