Preparation And Performances Of Modified Biomass Materials For Cu²⁺ And Ni²⁺ Adsorption From Aqueous Solutions

In recent decades,with the rapid development of industrial production,the emission of waste gas,water and solid waste from industrial manufacturing such as metallurgy,electroplating,tanning and chemical industry has increased,resulting in the increased pollution of heavy metals in water sources,which brought serious harm to humans and other organisms.Therefore,the treatment of heavy metal wastewater has become a currently common concern in the world.Cu²⁺and Ni²⁺are relatively common heavy metal ions in industrial wastewater.At present,the main methods for treating heavy metal wastewater include the method of ion exchange,chemical precipitation,membrane separation,adsorption,reverse osmosis and electrolysis,and the adsorption method is the most widely used.Adsorption method is an effective method to remove all kinds of pollutants by using the unique structure of adsorbent,especially in the application of heavy metal wastewater.The adsorption method is simple in operation and there are a wide variety of adsorbent materials,but the traditional adsorbents such as the activated carbon,inorganic nanomaterials are very expensive and non-renewable.While,as an emerging heavy metal adsorption material,the biomass adsorbent has a very low cost and wide range of sources,which has attracted much attention of scholars and become a research hotspot.In this paper,the chitosan,stalk of taro and mosaic leaves reed were respectively used as the raw materials and were chemically modified by using epichlorohydrin,N,N-dimethylformamide and diethylenetriamine to get the new type of biomass adsorption materials.They were used to remove Cu²⁺and Ni²⁺in wastewater,and then the effects and properties of the modified biomass adsorbent for removing Cu²⁺and Ni²⁺were discussed.This paper mainly includes the following three parts:?1?As raw materials,chitosan,taro and mosaic leaves reed stalks were used and modified to obtain the ammoniated absorbent materials?recorded as MCA,MTSA and MMLRSA respectively?.The 100 mL Cu²⁺and Ni²⁺solutions of 100 mg·L^-1 were tested for adsorption experiments on natural raw materials and modified aminated materials.According to the comparison of adsorption effects,it was found that the difference in adsorption effect before and after modification of chitosan was not significant,and therefore there was no need for further research.The adsorption effects of other two modified materials on heavy metals were significantly better,so the specific adsorption effect and performance were subsequently studied.?2?The physicochemical properties of MTSA were characterized by scanning electron microscopy and infrared spectroscopy and the influencing factors of adsorbing Cu²⁺and Ni²⁺by MTSA were studied.The results showed that the microspheres are formed on the surface of MTSA and have many gaps,which are beneficial for adsorption.The amino functional groups have been introduced in MTSA that are favorable for the adsorption of metal ions.As a result,the adsorption capacities of Cu²⁺and Ni²⁺(35.71 and 31.06 mg·g^-1)were increased about 4-6 times compared with unmodified taro stalk.In the experimental range,the adsorption of Cu²⁺is better at pH5.5 to 7.0,while Ni²⁺is better in the range of 7.0-8.5,and the best adsorbent dosage for adsorbing Cu²⁺and Ni²⁺are approximately 0.80 g.The equilibrium time of Cu²⁺and Ni²⁺are 960 min and 360 min,respectively,and the adsorption kinetics can be explained by the pseudo-second-order kinetic model.The adsorption belongs to the spontaneous and endothermic process.The adsorption isothermal data can be well described using Langmuir model.?3?The physicochemical properties of MMLRSA were characterized by scanning electron microscopy and infrared spectroscopy and the influencing factors of adsorbing Cu²⁺and Ni²⁺by MMLRSA were studied.The results showed that the structure of MMLRSA is loose,the micropores on the surface of the particles are more and smaller,and the amino groups have been introduced into MMLRSA by modification,which are favorable for adsorption.Within the scope of the experimental study,the optimal pH values for Cu²⁺and Ni²⁺adsorption on MMLRSA are approximately 5.5 and 7.5,respectively and the optimum adsorbent loading for Cu²⁺and Ni²⁺are approximately0.90 g.The adsorption capacity of Cu²⁺is saturated at about 480 min and Ni²⁺is about180 min.The pseudo-second-order kinetic model can better describe the adsorption process of Cu²⁺and Ni²⁺.It is the endothermic,spontaneous process at high temperatures.The process of adsorbing Cu²⁺and Ni²⁺by MMLRSA is more consistent with the Langmuir isotherm model and the adsorption capacities of Cu²⁺and Ni²⁺were31.25 and 25.06 mg·g^-1,respectively.In summary,the synthesis of two novel adsorption materials?MTSA and MMLRSA?were clarified and the adsorption properties of Cu²⁺and Ni²⁺were investigated in this paper.It found that MTSA and MMLRSA have the advantages of large adsorption capacity and stable adsorption so that the problem of small adsorption capacity and unstable adsorption about fiber materials were solved and have the broad prospects.