Studies On Preparation And Modification Of Spherical Sodium Lignosulphonate Resin And Its Adsorption Properties

With the industrial development,more and more urban vegetables are polluted by heavy metal seriously in China.Heavy metal accumulation in vegetables is obvious,some have reached a high level of residual,even higher than the national food sanitation standard.It is mainly due to the use of contaminated irrigation water.Heavy metal pollution has become a serious threat to people's health and life safety.Therefore,it is particularly important to remove heavy metal from the contaminated water.The main techniques that have been used to remove heavy metals from water include chemical precipitation,electrochemical method,membrane filtration,molecular imprinting method and adsorption method.Chemical precipitation can cause second pollution for the precipitating agent;the electrochemical method is mainly used in electroplating wastewater treatment,the deficiencies are large electricity consumption,high cost,and much oxygen and hydrogen evolution reaction;the major problem of membrane filtration is that the membrane components are expensive,and the membrane is vulnerable to be polluted during use,which causes the membrane is blocked and affect the effect;using molecular imprinting method,the water may be added new organic pollutants because the majority of molecularly imprinted polymers are synthesized by organic matter or the synthesis occurs in organic solvent;adsorption has been widely used in chemical industry,environmental protection,medical and biological engineering for water treatment because of its wide application range,good treatment effect,also because the useful materials are recyclable and the adsorbent can be repeated.The modification research of lignosulphonate(LS)has received great attention owing to its high production,cheap price,active groups,renewability,biodegradability and no toxicum.It is limited in practical application when the lignin adsorbent is powdered or granular whose pore structure and hydraulics performance is poor.Spherical lignin adsorbent is suitable for bed adsorption treatment because of its loose and hydrophilic network structure,large surface area,good permeability and hydraulic performance characteristics.At the same time,it is in favor of filling,cleaning,recycling and activating treatment.The adsorption capability of spherical sodium lignosulphonate(SLS)is not strong enough before being modified,it is necessary to be modified as matrix,functionalized with some ligands containing heterocycle,to improve its adsorption capability.This is not only comprehensive utilization of the natural resources but also management of papermaking,water treatment,hydrometallurgy,which bring about environmental pollutionBased on the review about the heavy metal pollution and lignin,removing heavy metal from the contaminated water for the purpose,the purified sodium lignosulphonate powder was successfully prepared into,and it was be modified as matrix and the adsorption properties of modified spherical sodium lignosulphonate resin were studied by the numbers.It is mainly manifested as follows:1.The sodium lignosulphonate powder were purified using cresol-oil of vitriol.The ingredients of powder before and after purification were compared,including moisture,ash and total sugar.The results show that,after purification,the content are reduced by 57.1%,76.1%,71.5%,respectively.The structures were compared with infrared spectroscopy(IR).The powder before and after purification were on the thermal decomposition by thermogravimetric analysis technology(TGA)instrument to investigate the thermal stability.2.Spherical sodium lignosulphonate resin(RLS)was prepared in principle of inverse suspension polymerization,using purified sodium lignosulphonate powder as raw material,epoxy chloropropane as cross-linking agent and NaOH as catalyst.The influence of experimental conditions such as the type of dispersed phase and dispersing agent,the dosage of dispersed phase,dispersing agent and epoxy chloropropane,the concentration of SLS and NaOH,stirring speed and reaction temperature were discussed.The single factor experiment and the response surface for preparation conditions were optimized,getting the best preparation process.The structures of SLS and RLS were compared with IR.The results show that,the modification is successful.The thermal stability is good through TGA experiment.3.Under the appropriate conditions,RLS reacted with ligands successfully,using RLS as matrix and sodium metal as catalyst,choosing one ligand from 2-Chloromethlbenzimidazole and 5-chloromethyl-lH-tetrazole.The influence of experimental conditions such as reaction solvent,reaction time,reaction temperature and mass ratio of reagents of synthesis were discussed.The single factor experiment and response surface analysis method for modified conditions were optimized,getting the best modification process.4.The adsorption capabilities for 6 kinds of heavy metal ions of RLS before and after modification were compared.The results show that,The adsorption capabilities of the modified RLS are stronger than the unmodified RLS.The adsorption properties of modified RLS for Cu(?),Ni(?),Zn(?),Pb(?),Cd(?)and Hg(?)were systematically investigated.Batch studies showed that the modified RLS had powerful adsorption capabilities for 6 kinds of heavy metal ions in HAc-NaAc medium at 298K.The statically saturated adsorption capacities of modified RLS for Cu(?),Ni(?),Zn(?),Pb(?),Cd(?)and Hg(?)were 74 mg/g,47 mg/g,42 mg/g,102 mg/g,54 mg/g and 112 mg/g,respectively.Isothermal adsorption curve including Langmuir model and Freundlich model,adsorption kinetics and thermodynamics parameters in different temperature were studied.Under the experimental concentration range,isotherms studies revealed that the adsorption followed the Langmuir model;kinetics studies showed that the adsorption process obeyed pseudo-second-order kinetics,which suggested that chemisorption was the rate controlling step.