Fabriction Of KGM-base Novel Adsorbents And Their Adsorption Ability Study

With the rapid development of industry,water pollution becomes an increasingly serious social problem,especially heavy metal ions pollut ion.Excessive levels of lead or cadmium ions in the drinking water will extremely affect people's health.Therefore,it is very urgent to remove the lead and cadmium ions from the water.Two novel adsorbents which are original from one popular polysacrride-K GM were creatively fabricated aiming to remove lead and cadmium ions in the aqueous.For the excellent advantages of adsorption method,such as easy operation,low cost,apparent adsorption efficiency etc.The key issue of adsorption method is the choice of the suitable adsorbent.Adsorbents used to removing heavy metals are generally classified into mineral adsorbent,microbes adsorbent,biomass adsorbent and so on.Seeking the novel adsorbent has never been stopped for the shortage of natural resources and the secondary pollution by the current adsorbents.K onjac glucanmannan is a kind of polysaccride,it has been attracted lots of research attentions for several advantages,such as abundance,renewability,degradability,non-toxicity,low cost and rich functional chemical groups.The konjac glucanmannan biological carbon(KGMB)is prepared via hydrothermal method;Microspheres which are composed of carboxymethyl konjac glucanmannan and the dopamine coating(CMKGM-PDA)is prepared via chemical modification method.Two kinds of materials were investigated as the heavy metal adsorbents by the static adsorption experiments.Their removal efficiency for the lead,cadmium ions,and the behavior of the recycling of them were systematically studied by considering the effect of the pH values,temperature,init ial concentration of the heavy metal ions and the content of the adsorbents.A series of characterization techniques such as TG,SEM-EDX,FT-IR and XPS were utilized to study the physical and chemical information of them and the adsorption mechanisms and behavior of heavy metal ions on them were explored.The study is meaningful for developing the noval environmental friendly adsorbents,it could provide certain theoretical basis for the application of these adsorbents.The following meaningful results can be concluded as:1.The adsoprion capacity of KGMB for single ions was 202.84 mg/g for Pb(?)and 137.55 mg/g for Cd(?)at 25 ? under the pH 5.7 with the dosage of 5 mg.The concentration of lead and cadmium ions solution is 50 mg/g.Each of the experiment lasts for 24 h.The adsorption process was consistent with pseudo-second-order kinetic and could be well described with Langmuir isotherm model.Thermodynamic analysis indicated that the adsorption process were exothermic and spontaneous in nature from 298.15 to 338.15 K.In reusability experiments,the adsorption capacity of Pb(?)and Cd(?)was 69.34 mg/g and 71.06 mg/g,respectively.The experiments were carried out for three times.2.The thermal stability of the KGMB was improved after the hydrothermal modification.Zeta potential of KGMB was negative at pH>2.3,which was beneficial to absorb the metal ions.The adsorption mechanism of lead and cadmium ions by KGMB were explored through the FT-IR,SEM-EDX and XPS.It was found that hydrogen ion of-O H of KGMB can be exchanged with Pb(?)and Cd(?),and there was electrostatic attraction between-O H of KGMB and metal ions(Pb(?)or Cd(?)).3.The adsoprion capacity of CMKGM-PDA was 75.19 mg/g for Pb(?)at 25 ? under the pH 6.0 with the dosage of 25 mg,the concentration of lead ion of 50 mg/g for 24 h;when the temperature was 45 ?,the adsoprion capacity was 153.37 mg/g for Pb(?).The adsorption process was consistent with pseudo-second-order kinetic and Langmuir isotherm model.The fitting maximum adsorption capacity was 95.2 mg/g at 25 ? and the adsorption capacity increased with the increasing of temperature.Thermodynamic studie s ind icated that the adsorption process were spontaneous,endothermic and entropy production in nature from 288 to 318 K.In reusability experiments,the adsorption capacity of Pb(?)was 27.5 mg/g after the five time recycle process when the concentration of lead solution was 18 mg/g.4.Thermal stability of the CMKGM-PDA was improved after the PDA modification.Zeta potential of CMKGM-PDA was negative at pH>3.65,which was beneficial to absorb the metal ions.The adsorption mechanis m of CMKGM-PDA for lead was explored through the FT-IR,SEM-EDX and XPS.It was found that there exist chelation between Pb(?)and-N H2 of dopamine when pH > 3.65.C helation interaction can be found between Pb(?)and oxygen of-O H onto CMKGM-PDA when pH < 3.65.5.The adsoprion capacity of CMKGM-PDA for Cd(?)was 21.5 mg/g at 25 ? when pH equals to 6 and the dosage of the adsorbent is 25 mg.The initia l concentration of cadmium ions aqueous solution is of 50 mg/g.Each of the experiment lasts for 24 h.The pseudo-second-order kinetic and Langmuir isotherm model are well consistent with the adsorption process.The fitted maximum adsorption capacity were 18.18 mg/g at 15 ? and 50.51 at 45 ?.With the increasing of the temperature,the adsorption capacity increased.The adsorption process were exothermic,spontaneous in nature from 288 to 318 K.In reusability experiments,the adsorption capacity of C d(?)was 17.2 mg/g a fter the five time recycle process when the concentration of cadmium solution was 50mg/g.6.The thermal stability of the CMKGM-PDA was improved after modification.Isoelectric point(IEP)test shows that the zeta potential of CMKGM-PDA was negative when the pH value is larger than 3.65.It was beneficial for the adsorption of the metal ions.Adsorption mechanism of Cd(?)was explored through the FT-IR,SEM-EDX and XPS.It was indicated that the there exists the chelation interactions between C d(?)and oxygen of-O H of CMKGM-PDA,chelation interactions can be found between Cd(?)and-N-H or-OH of CMKGM-PDA when the pH value is larger than 3.65.Two different modification methods were applied to modify konjac glucanmannan,two kinds of noval adsorbents(KGMB,CMKGM-PDA)were fabricated.Both of them presented good removal efficiency for lead and cadmium ions in aqueous solutions and exhibit the potentials for lead,cadmium ions wastewater treatment.