Preparation Of Sugarcane Bagasse Biosorbent And Its Adsorption Performance Of Heavy Metals In Water

With the rapid development of modern industry,heavy metal pollution is becoming more and more serious.As a novel heavy metal removal technology,biosorption has a wide application prospect.Sugarcane baggase?SCB?,as an agricultural by-productsan,is a promising biological adsorbent materials because of its large-tonnage and low-cost.In this paper,sugarcane baggase was chosen as the raw material to prepare two high-performance biosorbents for heavy metal in water,carboxyl-functional sagarcane bagasse?CF-SCB?and amino-functional sugarcane bagasse?AF-SCB?,through chemical modification by maleic anhydride and tetraethlenepentamine,respectively.The chemical and physical properties of sugarcane baggase before and after modification were characterized.Adsorption performance of the modified sugarcane bagasse biosorbents to remove heavy metals were investigated systematically.The adsorption mechanism of the two modified sugarcane bagasse biosorbents to remove heavy metals was discussed by characterization and analysis of factors.The main studied conclusions were summarized as follows:?1?Compared to SCB,CF-SCB and AF-SCB had rough surface and more close-knit and stable physical structure for the crystallinity increased.The carboxyl group was introduced into the molecular structure of CF-SCB and existed in the form of-COONa,and the surface negative charge quantity of CF-SCB was increased.The primary amine?-NH₂?and secondary amino?-NH-?groups was introduced into the molecular structure of AF-SCB,and the surface positive charge quantity of AF-SCB was increased.?2?After carboxyl-functional chemical modificition by maleic anhydride,the adsorption capacity of sugarcane bagasse biosorbents to remove Cd?II?were greatly improved.Under the condition of the solution pH 4.0 and 6.0,the maximum adsorption capacities for Cd?II?on CF-SCB were 120.19 mg/g and 134.23 mg/g,which were about 13 times and 10 times as that of SCB?9.22 mg/g and 13.20 mg/g?,respectively.The solution pH and coexistence cations had an effect on CF-SCB to adsorption Cd?II?.The optimum experimental range pH for CF-SCB adsorption of Cd?II?was 5.0⁸.0,the effect of coexistence cations was:Mg²⁺>Ca²⁺>K⁺>Na⁺.CF-SCB adsorption of Cd?II?could be descrided by the Langmuir model and the pseudo-second-order mode.The adsorption reaction activation energy Ea was 10.61 kJ/mol.The adsorption process was controlled by the chemical adsorption,and this adsorption reaction was spontaneous endothermic and entropy increased.The main adsorption mechanism of CF-SCB to remove Cd?II?was ion exchange adsorption,and the functional groups?-COONa?in the molecular structure of CF-SCB played an important role.CF-SCB had good recycling performance and the adsorption capacity of CF-SCB could be regenerated by 0.1 mol/L HCl.In weak acid or neutral low concentration mixed solution of heavy metals,CF-SCB had a good adsorption performance for cation heavy metal Cd?II?and Cu?II?.?3?After amino-functional chemical modificition by tetraethlenepentamine,the adsorption capacity of sugarcane bagasse biosorbents to remove Cr?VI?were significantly improved.In the solution of pH 4.0 and 6.0,the maximum adsorption capacities for Cr?VI?on AF-SCB were 188.68 mg/g and 153.37 mg/g,which were about 87 times and 90 times as that of SCB?2.18 mg/g and 1.70 mg/g?,respectively.The pH of solution and coexistence anion had an effects on AF-SCB to adsorption Cr?VI?.The optimized pH range for AF-SCB adsorption of Cr?VI?was 2.0⁵.0,the effects of coexistence anion was:CO₃^2->SO₄^2->NO₃^->Cl^-.AF-SCB adsorption of Cr?VI?could be fitted to the Langmuir model and the pseudo-second-order mode.And the adsorption reaction activation energy Ea was 6.95 kJ/mol.The adsorption process was controlled by physical process and chemical adsorption,and this adsorption reaction was spontaneous endothermic and entropy increased.In the process of AF-SCB to remove Cr?VI?under acid condition,the primary amino group?-NH₂?and secondary amino?-NH-?functional groups on the surface of AF-SCB play a role of the electrostatic adsorption.In the soft acid or neutral low concentration mixed solution of heavy metals,AF-SCB had good adsorption capacity for Cd?II?,Cu?II?and Cr?VI?.In conclusion,sugarcane bagasse was successfully introduced carboxyl,amino functional groups in the molecular structure through chemical modification by maleic anhydride and tetraethlenepentamine,respectively.Which could greatly improve the adsorption performance of sugarcane bagasse to remove heavy metals in water.Functionalization modified sugarcane bagasse,CF-SCB and AF-SCB,could be used as high-performance biosorbents to treatment of heavy metal in weak acid water.