An efficient and mild recycling of waste melamine formaldehyde foams by alkaline hydrolysis

Melamine formaldehyde foam(MFF)generates many poisonous chemicals through the traditional recycling methods for organic resin wastes.Herein,a high MFF degradation ratio of ca.97 wt.%was achieved under the mild conditions(160℃)in a NaOH–H2O system with ammelide and ammeline as the main degradation products.The alkaline solvent had an obvious corrosion effect for MFF,as indicated by scanning electron microscopy(SEM).The reaction process and products distribution were studied by Fourier-transform infrared spectroscopy(FTIR),X-ray photoelectron spectroscopy(XPS),and ^(13)C nuclear magnetic resonance(NMR).Besides,the MFF degradation products that have the similar chemical structures and bonding performances to those of melamine can be directly used as the raw material for synthesis of melamine urea-formaldehyde resins(MUFs).Moreover,the degradation system demonstrated here showed the high degradation efficiency after reusing for 7 times.The degradation process generated few harmful pollutants and no pre-or post-treatments were required,which proves its feasibility in the safe removal or recovery of waste MFF.

Preliminary Study on the Treatment Efficiency of Pasteurized Lime Thermal Alkaline Hydrolysis for Excess Activated Sludge and Reduction of Tetracycline Resistance Genes

Thermal alkaline hydrolysis is a common pretreatment method for the utilization of excess activated sludge(EAS).Owing to strict environment laws and need for better energy utilization,new methods were developed in this study to improve the efficiency of pretreatment method.Direct thermal hydrolysis(TH),pasteurized thermal hydrolysis(PTH),and alkaline pasteurized thermal hydrolysis(PTH+CaO and PTH+NaOH)methods were used to treat EAS.Each method was compared and analyzed in terms of dissolution in ammonium nitrogen(NH_(4)^(+)-N)and soluble COD(SCOD)in EAS.Furthermore,the removal of tetracycline resistance genes(TRGs)and class 1 transposon gene intI1 from EAS was investigated.The NH_(4)^(+)-N and SCOD concentrations in EAS treated by PTH were 1.24 and 2.58 times higher than those of TH.However,the removal efficiency of total TRGs and intI1 between the groups was comparable.The SCOD concentration of the PTH+NaOH group was 4.37 times higher than that of the PTH group,and the removal efficiency of total TRGs was increased by 9.52%compared with that by PTH.The NH_(4)^(+)-N and SCOD concentrations of the PTH+CaO group could reach 85.04%and 92.14%of the PTH+NaOH group,but the removal efficiency of total TRGs by PTH+CaO was 19.78%lower than that by PTH+NaOH.Thus,to reduce the financial cost in actual operation,lime(CaO)can be used instead of a strong alkali(NaOH),and pasteurized steam at 70℃ instead of conventional high-temperature heating to treat EAS.This study provides a reference for the development of alkaline hydrolysis under moderate temperatures along with the removal of TRGs in EAS.

Optimization of sugar production from Durian seeds via alkaline hydrolysis for second-generation bioethanol production

As one way to eliminate the issues found in the preceding generation,feedstock exploration in second-generation bioethanol production remains an issue,especially for a tropical country such as Indonesia.From exotic fruit by-products,durian holds a promising perspective that rests on its abundance,superb carbohydrate content and limited usage until now.This work presents the first-ever utilization of durian seeds for sugar production under optimized conditions through alkaline hydrolysis.A simple form of sugar was extracted by varying four parameters,namely substrate loading,NaOH concentration,hydrolysis time and hydrolysis temperature.Response surface methodology based on the Box-Behnken design was employed to outline the most optimum parameter values.Analysis of variance revealed that the quadratic model fit the data appropriately with the order of significance as substrate loading>hydrolysis time>NaOH concentration>hydrolysis temperature.The optimized conditions for reducing sugar yield,as high as 2.140 g/L,corresponded to<50 g/L substrate loading,0.522 M NaOH,60 minutes of hydrolysis time and 80oC hydrolysis temperature.The possible ethanol content of 1.094 g/L was also expected under optimized conditions,demonstrating great potential in second-generation bioethanol production.

Towards recycling purpose:Converting PET plastic waste back to terephthalic acid using pH-responsive phase transfer catalyst

Converting polyethylene terephthalate(PET)wastes to its monomer and valuable chemicals via ecofriendly chemical method is still a challenge task.Previously,phase transfer catalysts used for alkaline hydrolysis were soluble in reaction media and hardly separated after reaction.Here,we reported several pH-responsive catalysts combined alkyl quaternary ammonium units with heteropolyacid anion for achieving stepwise product/catalyst separation and catalyst recycling.The properties of homogeneous/heterogeneous transfer behavior allow catalyst to be easily separated from reaction media by adjusting of pH value.Among them,[C_(16)H_(33)N(CH_(3))_(3)]_(3)PW_(12)O_(40)(abbreviated as[CTA]_(3)PW)exhibits the highest activity and the most suitable pH responsive values.Such a pH triggered switchable catalytic system not only shows good performance for depolymerization of pure PET,but also some real PET wastes such as coloured trays and PE/PET complex films could be completely degraded into terephthalic acid.Additionally,the reaction kinetics and activation energy of PET alkaline hydrolysis also studied with and without pH-responsive[CTA]_(3)PW.

Determination of Omethoateby Cathodically SweepingOscillopolarography

Determination of omethoate by cathodically sweeping oscillopolarography is described. The product of the alkaline hydrolysis exhibited a sensitive second derivative wave at ?0.50 V (vs. SCE) in a 1.0 ×10?5mol/L sodium dodecylbenzene sulfonate (SDBS)+0.1 mol/L HAc-NaAc (pH 4.0) buffer. The peak current was linearly proportional to the concentration of omethoate in the range from 6.4×10?7 to 5.1×10?5 mol/L. The detection limit is 2.0×10?7 mol/L with the relative standard derivation (RSD) of 3.5%. The hydrolysis procedure and the electrode reaction were studied by voltammetry.

Determination of Isocarbophos by Cathodically Sweeping Oscilliopolarography

Determination of isocarbophos by cathodically sweeping oscilliopolarography is described. In a 1.0×10?5 mol/L sodium dodecylbenzene sulfonate (SDS)+0.1 mol/L HAC-NaAC (pH=4.0) buffer medium, isocarbophos and its alkaline hydrolysate exhibited sensitive second derivative wave at ?0.50 V and ?0.48 V respectively. The peak current was linearly proportional to the concentration of isocarbophos in the range of 5.40×10?6?1.05×10?4 mol/L by detecting isocarbophos directly. The detection limit was 3.60×10?6 mol/L with the relative standard derivation (RSD) of 7.3%. By employing an alkaline hydrolysis, the peak current was linearly proportional to the concentration of isocarbophos in the range from 7.70×10?7 mol/L to 1.24×10?4 mol/L, and the detection limit was 5.80×10?7 mol/L with RSD of 3.1%. The hydrolysis procedure and the electrode reaction were studied by voltammetry.

Digestibility Improvement of Sorted Waste with Alkaline Hydrothermal Pretreatment

The digestibility of sorted municipal solid waste （MSW） is often limited by the high content of structured green waste. The objectives of this study are to investigate the effect of alkaline hydrothermal pretreatment on the anaerobic digestion of sorted waste and to analyze the biogas production of different parts of the waste. The waste was hydrothermally pretreated in a dilute alkali solution. The hydrolysis product was then incubated in a 500 mL saline bottle to determine the biochemical methane potential （BMP） under mesophilic anaerobic conditions. The optimum hydrothermal condition was 170℃ at 4 g NaOH/100 g solid for one hour. The concentration of chemical oxygen demand （COD） was 13 936 mg/L and the methane yield was 164 mL/g volatile solid （VS） for 6 days incubation at the optimum conditions. The biogas production was increased more than 50% over the control, with the methane conversion ratio on a carbon basis enhanced to 30.6%. The organic part of the sorted waste was mainly kitchen garbage and leaves. Model kitchen garbage completely liquified at 130℃ for one hour had a methane yield of 276 mL/g VS. The alkali addition slightly enhanced the hydrolyzation rate and methane yield. The biogas potential of leaves was improved by pretreatment at above 150℃ under alkaline conditions.

High-yield production of secoisolariciresinol diglucoside from flaxseed hull by extraction with alcoholic ammonium hydroxide and chromatography on microporous resin

This study used alcoholic ammonium hydroxide to directly hydrolyze and extract secoisolariciresinol diglucoside(SDG)from flaxseed hull in a one pot reaction.The optimal extraction conditions,including the concentration of ammonium hydroxide,extraction time,and temperature,were examined in single factor experiments,followed by response surface methodology(RSM)with 3-level,3-factor Box-Behnken experiments.As a result,the optimal extraction conditions were determined as follows:material-liquid ratio 1:20,percentage of reagent ammonium hydroxide(25–28%of NH3 in water)in ethanol 33.7%(pH=12.9),extraction time 4.9 h,and extraction temperature 75.3°C.Under these conditions,the yield of SDG,as measured by ultra-high-performance liquid chromatography-mass spectrometry,was 23.3 mg/g,consistent with the predicted content of SDG in flaxseed hull(23.0 mg/g).Further,30.0 g of pulverized flaxseed hull was extracted under the optimal conditions,and the extract was subjected to a single run of macroporous resin chromatography to obtain 772.1 mg of a fraction with an SDG content exceeding 76.1%.Subsequent chromatography on Sephadex LH20,yielded 602.8 mg SDG of 98.0%purity,and the yield was 20.1 mg/g(2.0%)from flaxseed hulls.Thus,one-pot hydrolysis and extraction of SDG using alcoholic ammonium hydroxide is simple,and of high-yield.