Applied Basic Research On Photo/thermal Controllable Degradation Of Polyethylene Films Over MoS₂/Bi₂S₃/Ni₃S₄

The research was supported by the Nuclear Energy Special Project（13ZG610301）.The catalyst of MoS₂/Bi₂S₃/Ni₃S₄ was synthesized via hydrothermal and thermocatalytic degradation of Methylene Blue（MB）considered as model organic pollutant at near room-temperature firstly,it was investigated excellent thermocatalytic degradation ability,then further discussed the simulated UV degradation,thermocatalytic degradation and buried in soil degradation of polymeric films add MoS₂/Bi₂S₃/Ni₃S₄ in a different proportion of added to the polyethylene film.The effect of degradation temperature to the LDPE composite films were investigated also.As a result,the catalyst has excellent thermal catalytic and light/heat catalytic ability.The research may provide reference and guidance for organic effluents disposal and degradation of polyethyle through thermocatalytic degradation to solve the problem of conventional photocatalytic polyethylene mulch inadequate see light parts or covering light refractory,the main results were as follows:（1）A novel thermal sensitiver of MoS₂/Bi₂S₃/Ni₃S₄ was synthesized by reflux method and used for degradation of methylene blue（MB）under darkness at room temperature.Results showed that the thermocatalytic activity of MoS₂/Bi₂S₃/Ni₃S₄ was excellent and lead to acute thermodegradation of MB.At the optimal component condition,when concentration of MB was 20 mg/L,the removal rate of the MB could be achieved 98.59% after 2.5 h at the reaction temperature of 40℃.The methylene blue molecules were degraded into toluene,or even CO2 and H2 O over MoS₂/Bi₂S₃/Ni₃S₄ power.Moreover,the kinetics of degradation rate was modeled considering that it was found similarly to Langmuir-Hinshelwood behavior which degree of correlation was up to 0.993,and a tentative mechanism was objectively established.Herein the insight into degradation patterns of organic pollutant over thermal excitation may further enlarge applications for wastewater treatment.（2）The results showed that MoS₂/Bi₂S₃/Ni₃S₄ had a high photocatalesis activity in degrading LDPE films after irradiated 10 days at 50 ℃,and the degradation behavior of LDPE composited film was obvious when the content ofMoS₂/Bi₂S₃/Ni₃S₄ was 3%.At this time,the Tensile strength and Max extend was reduced to 22.83 MPa and 166.15 mm,the surface roughness increased by19.52 nm.While the contact angle,decomposition temperature and number-average molecular weight reduced by 32.44 °,33 ℃ and 88260,respectively.At the same time,carbonyl groups were detected in LDPE composite films and there were holes on the surface of films around the catalyst.（3）After thermodegradation for 90 days at 50 ℃ in dark,LDPE composite films were degraded by MoS₂/Bi₂S₃/Ni₃S₄ obviously,and LDPE composite film had the best degradation effect when the content of catalyst was 3%.The film has been loss of mechanical properties,and tensile strength and max extend reduced by20.38 MPa and 148.10 mm,respectively.The decomposition temperature,contact angle and number-average molecular weight reduced by 25 ℃,36.41 °and 83259,respectively.While,the surface roughness increased by 19.42 nm.At the same time,broken and holes were observed on the surface of LDPE film and carbonyl groups were also detected after thermal degration.（4）The study found that the LDPE composite film has been degraded when the higher the temperature and the longer the reaction time.In the process of simulated UV degradation,the loss of mechanical properties as the degradation increases with the rising of temperature,and its degradation of the induction period is the faster after 10 days.In thermal process of LDPE composite membrane,the degradation of LDPE composite membrane at 50 ℃ effect is obviously better than that of 30℃ and 40℃,and the induction period is shorter.Furthermore,photocatalysis and thermal degradation time of LDPE composite film can be designed by temperature.（5）The composite film has been degraded when buried in soil.After buried in soil for 90 days,the tensile strength and max extend was reduced to 19.84 MPa and 152.44 mm,respectively;decomposition temperature and contact angle reduce by 23℃ and 26.09°,the surface roughness increased by 15.15 nm.The same time,carboxyl and carbonyl groups were detected and the surface of LDPE film was destroyed by the catalyst.