| In this study,the concentration of total volatile organic compounds（TVOC）and formaldehyde in typical public place such as furniture markets,malls,hotels,and entertainment places,in Guangxi typical cities（Guilin,Liuzhou,and Nanning）,were detected and analysized by organic gas detector and formaldehyde detector.The distribution of indoor formaldehyde concentrations emission from surface decorated wood based panel in simulation space were simulated by adopting Airpak fluid analysis software.The influence of temperature,humidity and ventilation rate on formaldehyde emission from surface decorated wood based panel were investigated in the environment chamber and simulation space.The formaldehyde mathematical model was thus set up combined with Mass transfer theory.The low formaldehyde modification technology of PVAc emulsion was investigated by means of Box-Behnken experimental design method.The low formaldehyde modification mechanism and pyrolysis mechanism of PVAc emulsions were also discussed by adopting Gas Chromatography-Mass Spectrometer analysis（GC-MS）,Fourier transform infrared analysis（FT-IR）,thermal gravimetric analyzer（TG-DTG）,and differential scanning calorimeter（DSC）.The preparation technology,of CuxO/Bi2O3 composite material used for formaldehyde treatment was investigated by means of Plackett-Burman combined with the central composite design（CCD）.The reaction mechanism of photocatalytic formaldehyde degradation by CuxO/Bi2O3 composite material were also discussed by means of X-Ray diffraction analysis（XRD）,scanning electron microscope analysis（SEM）,and ultraviolet visible analysis（UV-vis）,and the main results showed that:（1）The mean concentrations of formaldehyde and TVOC at four kinds of public places in a descending order as furniture market>mall>hotel>entertainment place.The highest mean concentrations of formaldehyde and TVOC of furniture market in Nanning city can respectively reach 0.174 mg/m3 and 0.617 mg/m3,which were 1.74 times and 1.03 times of the allowable standard limit.（2）The spatial distribution of formaldehyde concentration in simulation space was correlated significantly with pollution source position,ventilation rate,temperature,etc.The concentrations of formaldehyde in closed simulation space were respectively 0.144 mg/m3 and 0.496 mg/m3 under the normal temperature（20℃）and high temperature（35℃）.While the concentrations of formaldehyde in ventilation（2.5h-1）simulation space under the normal temperature（20℃）and high temperature（35℃）were 0.085 mg/m3 and 0.355mg/m3,respectively.The maxium difference between observed and simulated value of formaldehyde concentration was 12.9%.（3）The formaldehyde emissions from surface decorated density board,surface decorated plywood,and surface decorated particle board can be divided into the quick-release,slow-release,and release saturation phases over time.The concentration of formaldehyde released from surface decorated wood based panel increase with rise of temperature and humidity,but would decrease with the rise of ventilation rate,and the corresponding formaldehyde concentrations were 1.290 mg/m3,0.550 mg/m3,and 0.520 mg/m3,respectively.（4）The concentration of formaldehyde released from surface decorated wood based panel-increase with rise of temperature.The concentrations of formaldehyde in simulation spaces which were higher（0.107 mg/m3～0.252 mg/m3）in summer and were lower during winter（0.006 mg/m3～0.037 mg/m3）.The formaldehyde pollution caused by surface decorated wood based panel at simulation spaces in a descending order as surface decorated density board>surface decorated plywood>surface decorated particle board.（5）The formaldehyde emission model of surface decorated wood based panel was:Compared with experimental test data,the simulation results of formaldehyde concentrations emission from surface decorated density board,surface decorated plywood,and surface decorated particle board,predicted by adopting mathematical models showed a good fit,and the maximum error of formaldehyde concentrations between predicted and measured were 12%,10%,and 12%.（6）The modifying agent can effectively reduce free formaldehyde content of PVAc emulsion.The influence of free formaldehyde content of PVAc emulsion in a descending order as sulfanilamide concentration>N,N-Dimethyl-1,2-ethanediamine concentration>aluminium sulfate concentration>polyving akohol concentration.The optimal modification technology was obtained:sulfanilamide concentration was 15wt%,N,N-Dimethyl-1,2-ethanediamine concentration was 3wt%,aluminium sulfate concentration was 3wt%,polyving akohol concentration was 3wt%,and free formaldehyde content of PVAc emulsion modified by this modification technology has decreased by 88.9%.The reaction equation of free formaldehyde in PVAc emulsions reacted with N,N-Dimethyl-1,2-ethanediamine and sulfanilamide in the process of modification may were 7C4H12N2+16CH2O=5C7H17N+4C2H4N2O2+CHNO+7H2O,and 2C6H8N2O2S+3CH2O=C3H4N2O+2C6H7SO2N+2H2O,respectively.（7）The overall pyrogenic decomposition process of PVAc emulsion before and after modification could be divided into three stages of drying dehydration,fast pyrolysis and slow pyrolysis.The activation energy（E）,enthalpy change（△H）,entropy change（△S）,and Gibbs free energy（AG）of unmodified PVAc emulsion with the pyrolysis temperature between 220℃410’C and between 410℃～450℃ were respectively 113.82 KJ/mol,108.68 KJ/mol,-137.24 J/（mol·K）,193.53 KJ/mol,and 87.28 KJ/mol,81.48 KJ/mol,-162.31 J/（mol·K）,and 216.20 KJ/mol.The activation energy（E）,enthalpy change（AH）,entropy change（AS）,and Gibbs free energy（AG）of modified PVAc emulsion with the pyrolysis temperature between 210℃～440℃were respectively 142.79 KJ/mol,137.94 KJ/mol,-92.35 J/（mol·K）,and 191.86 KJ/mol,and had improved compared to the PVAc emulsion before modification.The decomposition of PVAc emulsions before and after modification are all belongs to the non-spontaneously endothermic reaction.（8）CuxO/Bi2O3 composite material has a significant effect on the removal of formaldehyde.The influence of technological factors for the formaldehyde removal rate of CuxO/Bi2O3 composite material in a descending order as lactic acid concentration>polyethylene glycol 600 concentration>sintering time>bismuth nitrate doping amount>electrodeposition temperature>anhydrous ethanol concentration>electrodeposition time>sintering temperature>electrolyte pH>current density;The optimal preparation technology was obtained:copper sulfate concentration was 0.4 mol/L,lactic acid concentration was 4.28 mol/L,anhydrous ethanol concentration was 15wt%,polyethylene glycol 600 concentration was 4.87mt%.electrolyte pH value was 8.5,current density was 8 mA/cm2,electrodeposition time was 60 min,electrodeposition temperature was 70℃,bismuth nitrate doping amount was 45.83 g,sintering temperature was 350℃,and sintering time was 193.93 min,and the corresponded formaldehyde removal rate was 87.61%.The formaldehyde removal rate of the CuxO/Bi2O3 composite material had only declined by 4.1%after used for 5 times,which showed that the CuxO/Bi2O3 composite material had better cycle stability for the photodegradation of formaldehyde.（9）The results from characterization and analyzation for CuxO/Bi2O3 composite material showed that compound material of the ingredients Cu2O,CuO,and Bi2O3 had achieved the codeposition.The prepared CuxO/Bi2O3 composite material had uniform and compact structure,and exhibit a broad absorption in the range of 265 nm～560 nm.The spectral response range of the CuxO/Bi2O3 composite material was clearly enlarged,especially on the strengthening the photocatalytic reaction ability under UV and visible light. |
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