Research On Adsorption Of 4-Chlorophenol By Modified Biochar And Treatment Efficiency Of Adsorbent By Microwave Activating PDS

Chlorophenols are biologically toxic and refractory,which cannot be effectively treated by traditional biological treatment.Oxygen-limited pyrolysis of biomass can obtain the biochar,which does not only reduce the emission of greenhouse gases but also reduce the impact of smog caused by combustion.Moreover,biochar also performs well in adsorption and catalysis.In view of the functional characteristics of biochar,this article aims to prepare the biochar that has high adsorption ability to 4-chlorophenol?4-CP?and can efficiently activate persulfate in a microwave field,finally,a reliable method is proposed which can quickly treat water contaminants using adsorbent materials,which is a convenient treatment.Using wheat straw as a material to prepare modified biochar by high-temperature oxygen-limited pyrolysis method.Combined with Zn Cl2 to prepare modified biochar and uses it as an adsorbent to adsorb 4-CP in water.In this paper,the surface area and pore size,functional groups,morphology,element composition,and persistent free radicals of biochar were analyzed and determined.Combined with the study of the adsorption equilibrium model,found that after being modified by Zn Cl2,the surface area of biochar increase to near 130 times to 234.2m2/g,and the saturated adsorption capacity of 4-CP reached 111.0 mg/g.Adsorption thermodynamics and adsorption kinetics studied on the adsorption process prove that the adsorption of 4-CP by modified biochar is a spontaneous exothermic process,and the chaos of the system decreased.The research on the adsorption mechanism of modified biochar to 4-CP shows that there is hydrogen bonding,van der Waals force,hydrophobic bonding force,and ?-? adsorption in the adsorption process.Modified biochar?BC?adsorbing 4-CP can efficiently activate persulfate?PDS?and realize the harmless regeneration of adsorbed BC in the microwave field.At room temperature,the BC/PDS system was constructed,and when the reaction temperature was increased to 80 ?,the TH-BC/PDS and MW-BC/PDS systems were constructed using water bath thermal?TH?and microwave?MW?heating methods,respectively.Experimental studied on reaction kinetics show that the three systems of BC/PDS,TH-BC/PDS and MW-BC/PDS all conform to pseudo-first-order reaction kinetics.Compared with the BC/PDS system,the rate constants of the TH-BC/PDS system,and the MW-BC/PDS system were increased to 3.25 times and 13 times,respectively,reaching to 0.0247 min-1 and 0.1014 min-1.In the process of BC harmless treatment,the chloride ion concentration is used as an indicator to evaluate the ability of MW-BC/PDS system to reduce the toxicity of BC.When the mass ratio of PDS to BC is 2/1,after treatment at a microwave temperature of 80 ? for 20 min,36.9% of chloride ions can be effectively removed,reducing the toxicity of the adsorbent.Cyclic experiment results show that the regeneration rate of BC can reach 89.0%.Combined experimental tests with references,the mechanism of the harmless regeneration process of BC was analysed.The experimental test combined with the theoretical analysis results showed that there are radical and non-radical degradation pathways in the harmless treatment process,the radical degradation mechanism is the mainly pathway,non-radical degradation mechanism is the supplement pathway.There are radical and non-radical degradation paths in the harmless process,and sulfate radicals(SO₄^-·)plays a major role,SO₄^-·is produced when the PDS is activated by microwave and the oxygen-containing groups and persistent free radicals?PFRs?of biochar;in the non-radical path,the electron transport of the carbon skeleton and the oxidizability of ¹O₂ are degraded The process made major contributions.