Preparation And Properties Of Rice Husk Composite Modified Materials

With the development of the times,more and more attention has been paid to ecological environment protection and comprehensive utilization of renewable resources.As a natural renewable resource,rice husk has become a research hotspot because of its advantages of cheap,easy availability and natural degradation.In this paper,rice husk was modified by etherification and esterification using chloroacetic acid as etherifying agent and octenyl succinic anhydride as esterifying agent.Carboxyl groups were introduced into rice husk cellulose through etherification reaction,and then long-chain hydrophobic groups were introduced through esterification reaction to prepare composite modified rice husks with the ability of adsorbing heavy metal ions and oil pollution at the same time.The etherification reaction uses acid treated rice husk as raw material,first alkali treated with NaOH,and then etherification modified with chloroacetic acid to obtain etherified rice husk.The experiment took the removal rate of Cu²⁺adsorbed by etherified rice husk as the index,and studied the effect of reaction temperature,reaction time,water-alcohol ratio,the dosage of NaOH and the dosage of chloroacetic acid on the preparation of etherified rice husks.The single factor experimental method was used in the study,and response surface methodology was carried out on this basis to explore the optimal process conditions for the preparation of etherified rice husk.The research results showed that the optimal conditions for the preparation of etherified rice husks were as follows:the reaction temperature was 65℃,the reaction time was 6.2h,the water-alcohol ratio was 0.3,the dosage of NaOH was 0.91g/g rice husk,and the dosage of chloroacetic acid was 1.63g/g rice husk.Under the optimal process conditions,the removal rate of heavy metal ion Cu²⁺was 96.20%.The esterification reaction is to prepare etherified-esterified rice husk by using octenyl succinic anhydride as esterification agent on the basis of etherified rice husk.In the experiment,the oil removal rate was used as the index,and the single factor experimental method was used in the experiment,and the response surface test was carried out to study the effects of the dosage of octenyl succinic anhydride,reaction temperature,reaction time and reaction p H on the preparation of the etherified-esterified rice husk.The research results showed that the optimal esterification process conditions for the preparation of etherified-esterified rice husk were as follows:the dosage of octenyl succinic anhydride was 3.22g/g rice husk,the reaction temperature was 73°C,the reaction time was8h,and the reaction p H was 8.7.Under these conditions,the oil removal rate of the modified rice husk can reach 71.90%.The influence of the dosage of adsorbent,adsorption time,adsorption temperature and p H on the adsorption performance of modified rice husk was explored in the optimization experiment of adsorption process parameters.The experimental results showed that the best process conditions for the adsorption of Cu²⁺by etherified rice husk were as follows:the dosage of adsorbent was 4g/L,the adsorption time was 60min,the adsorption temperature was 25℃,and the adsorption p H was 5.5.Under these conditions,the removal rate of Cu²⁺in wastewater by etherified rice husk can reach99.39%.The best process conditions for the adsorption of oil by etherified-esterified rice husks were as follows:the dosage of adsorbent was 8g/L,the adsorption time was 80min,the adsorption temperature was 35℃,and the adsorption p H was 7.Under these conditions,the oil removal rate of etherified-esterified rice husk was 75.25%.The samples before and after modification were characterized by FT-IR,SEM and contact angle.According to FT-IR,it can be seen that new functional groups were successfully introduced into rice husk;the appearance and morphology of the rice husk before and after modification can be observed by SEM;the hydrophobic properties of the modified material can be characterized by the measurement of contact angle.The adsorption process of modified rice husk was further studied by adsorption kinetic experiments.The experimental results showed that the adsorption process of modified rice husk for heavy metal ion Cu²⁺or engine oil was consistent with the pseudo-second-order kinetic model.