Synthesis And Applications Of Waste Hippophae Rhamnoides Linn Branches Based Superabsorbent Composite

Hippophae rhamnoides Linn. branches, as a byproduct of Hippophae rhamnoides Linn., have various advantages including that they are very inexpensive, incredibly abundant, completely biodegradable, and clearly renewable. However, great quantities of Hippophae rhamnoides Linn. branch have low utilization at present, mainly as agricultural waste.The common management options of these agricultural wastes, such as discarding outside, burning with fire and burying underground are characterized by serious resource waste and significant environmental pollution. To find the effective uses of excess waste Hippophae rhamnoides Linn. branch resources, a cost-effectiveandeco-friendly hybrid superabsorbent based on superabsorbent polymers were successfully synthesized using waste Hippophae rhamnoides Linn.branchesas raw materials. The obtained composite can overcome the shortcomings of synthetic superabsorbent polymers including high production cost, weak salt resistance, and poor biodegradability; and on this basis we proposed dopamine-mediated method to simplify the pretreatment of Hippophae rhamnoides Linn. branches and prepared a novel superabsorbent composite; to make the most of superabsorbent composite, HBP/PAA was applied to dye wastewater treatment. And the adsorption capability has been investigated. The main research contents are listed as follows:(1) Synthesis and properties of Hippophae rhamnoides Linn. branch powder grafted PAA superabsorbent compositesHippophae rhamnoides Linn. branch powder grafted PAA(HBP/PAA) superabsorbent composites were synthesized by free-radical aqueous copolymerization, using waste Hippophae rhamnoides Linn. branch powder as matrix, acrylic acid as monomer, potassium persulfate(K2S2O8) as initiator and N,N’-Methylenebisacrylamide(MBA) as crosslinker. FT-IR and FE-SEM indicated that the obtained superabsorbent composites had surface cross-linking traits through the graft of acrylic acid onto HBP backbone. The composites had the best absorbency of 190.0 g/g in distilled water and 40.0 g/g in 0.9 wt% Na Cl solutions, and the corresponding equilibrium time was 16 and 10 min, respectively. The swelling kinetics of HBP/PAA in distilled water could be fitted well with a pseudo-second-order kinetic model.The water absorbency at equilibrium decreased as the concentration of various external saline solutions increased, and the absorbency of the composites in the studied salt solutions was in the order: Na Cl >Ca Cl2 >Fe Cl3. The water retention capacity reduced as the temperature changed from 25 oC to 80 oC. Moreover, the absorbencies ability in distilled water and 0.9 wt% Na Cl aqueous solution via five cycles remained about 91.8 % and 86.7 % of the original maximum value.(2) Synthesis and properties of an ecofriendly superabsorbent composite by grafting the poly(acrylic acid) onto the surface of dopamine-coated Hippophae rhamnoides Linn. branchWith the purpose of decreasing production costs and mitigating negative effects on the environment, an ecofriendly superabsorbent composite(PD-HBP/PAA) was synthesized by grafting poly(acrylic acid) onto the surface of dopamine-coated waste Hippophae rhamnoides Linn. branches. The structure of the obtained products was analyzed using Fourier transforminfrared(FTIR) spectroscopy and scanning electron microscopy(SEM). The effects of salt concentration, cation type, and reswelling time on water absorbency were examined further. The results showed that the swelling behaviors of the superabsorbent composite were highly sensitive to the concentration of salt solution, cation type, and reswelling time. On the basis of these investigations, it is believed that the obtained PD-HBP/PAA could have potential applications in industrial areas because of their water superabsorption capacity, high reswelling capability, and cost-effective and ecofriendly preparation and use. The proposed technology can also be extended to the synthesis of other natural biological resources and organic hybrid materials with similar structures.(3) Enhanced adsorptive removal of safranine T from aqueous solutions by HBP/PAAsuperabsorbent composite: kinetics, equilibrium, and thermodynamics.The adsorption progresses of Safranine T on the surface of HBP/PAA superabsorbent composite were systematically investigated. More specifically, the effects of solution p H, contact time, initial concentration and temperature were evaluated, respectively. The experimental results showed the adsorption capacity of HBP/PAA at 298.15 K could reach up to 56.0 mg/g; besides, kinetics studies showed that pseudo-second-order kinetic model adequately described the adsorption behavior. The adsorption experimental data could be fitted well a Langmuir isotherm model. Thermodynamic analyses showed that the ST adsorption was a physisorption endothermic process. On the basis of these investigations, it is believed that the HBP/PAA adsorbent could have potential applications in sewage disposalareas because of their considerable adsorption capacities and cost-effective and eco-friendly preparation and use.