Studyon Adsorption Of Cu(Ⅱ) With Biomass

In this paper, four kinds of biomass such as rice straw, wheat straw, corn stalk and peanut shell were used as raw materials, each experienced crushing, carbonizing and modifying, which delivers 12 adsorbents of different properties. Studies on adsorbing Cu (Ⅱ) using them have been conducted. Different methods were used to characterize performance of the adsorbents. The influences of adsorbing time, pH, dosage, reaction temperature, ionic strength and competitive adsorption against Cd(Ⅱ) were investigated. Adsorption isotherm models, thermodynamics models and kineticsmodels of the adsorption process between biomass adsorbent and Cu(Ⅱ) were systematic studied. Regeneration of the adsorbents were studied experimentally and analytically. The main research contents and conclusions are as follows:1. Performance characterization of intact materials, carbonized materials and modified materials. The characterization results reveal that the surface of the four kinds of raw materials was of non-porous structure. The surface of the adsorbent was smooth and orderly structure with small specific surface area. Four kinds of biomass raw materials were from macro-porous materials into porous adsorption materials through high temperature carbonization. Carbonized materials had a porous structure, which greatly increased the specific surface area, so the adsorption capacity of pollutants had increased a lot. Modified materials from biomass raw materials were made by zinc chloride combined with microwave irradiation. The modification made the fiber material dehydro aromatization, while the formation of relatively rich pore made the surface area of adsorbent increased. The polymer functional groups were formed to conducive to the adsorption of heavy metals with combination of simple functional groups. The activation of microwave destroyed the alkaline functional groups, gathered the acidic functional groups together which made the adsorption capacity of modified biomass a certain increase. The adsorption performance of the modified adsorbent of rice straw, wheat straw and corn stalk had been significantly mproved compared with their raw materials. The adsorption performance of modified peanut shell had a relatively large increase.2. Adsorption performance of intact materials, carbonized materials and modified materials. From the results, the adsorption performance of modified materials and carbonized material were much better than the intact material. The adsorption performance of modified materials was a little better than the carbonized materials. The adsorption performance of peanut shell was better than the other three kinds of adsorption material of the same class.The adsorption quantity of modified peanut shell was the highest, reached 46.2mg/g. The adsorption quantity of carbonized peanut shell reached 43.1mg/g. They were all far above the adsorption quantity of intact peanut shell which was 29.2 mg/g.3. The effect of reaction conditions (adsorption time,carbonization temperature, pH, adsorbent dosage, temperature, ionic strength and competitive adsorption againstCd(Ⅱ)) on absorption of Cu(Ⅱ) with biomass.The adsorption equilibrium time of three kinds of materials was in basic 8-12h. The adsorption quantity of Cu(Ⅱ) with carbonized materials increased with the carbonization temperature. The adsorption quantity increased with pH, when the pH value was between 1-6. When the pH value achieved 6, the adsorption quantity reached the highest. The adsorption quantity increased with the increase of the adsorbent dosage of three kinds of biomass.When the dosage increased to a certain extent, the removal rate of Cu(Ⅱ) didn’t change obviously. The optimal dosage was 0.20g of these three kinds of biomass. The adsorption quantity increased with temperature. Adsorption quantity decreased with the increasing ionic strength. Two valence ions inhibit the adsorption stronger than monovalent ions. As the ability of inhibition of adsorption, two valence ons were stronger than monovalent ions. In general, the adsorption quantity was relatively small decline, so the ionic strength on effects of adsorption capacity of biomass was small.4. Research into the dynamics of adsorption. From the adsorption kinetics and model fitting analysis, the adsorption of Cu (Ⅱ) process followed the pseudo-first-order kinetics equation and the pseudo-second-order kinetics equation. Compared to the pseudo-first-order kinetics equation, the pseudo-second-order kinetics equation could better describe the adsorption process. The pseudo-second-order kinetics equation reflected that the adsorption rate was proportional to the square of the concentration of Cu(Ⅱ).5. Adsorption thermodynamics research. From the adsorption thermodynamics and model fitting analysis, the adsorption isotherm of intact materials, carbonized materials and modified materials to adsorb Cu(Ⅱ) conformed to the Langmuir isotherm model and Freundlich isotherm model. The adsorption of Cu(Ⅱ) was between single molecular layer and polymolecular layer. The adsorbent surface was not uniform and stable, which had a certain influence on the adsorption process. Thermodynamic study showed that in the process of adsorption of Cu (Ⅱ) by intact materials, carbonized materials and modified materials, △G<0、△H>0, △ S>0. It was showed that the adsorption process was a spontaneous reaction, and was a process of heat adsorption. So raising temperature was good to adsorption. The adsorption process was also under a disorder of the state.6. Adsorbent regeneration research. From the regeneration results, removal effect of Cu (Ⅱ) on the adsorbent was:HCl>NaCl>deionized water with HC1 solution, NaCl solution and deionized water to regenerate the adsorbent. Through three cycles of adsorption and regeneration experiments, the adsorption ability of biomass to Cu (Ⅱ) decreased smaller. These three kinds of biomass materials can repeat the adsorption of metal ions in aqueous solution.This study provided a new idea with high efficiency and low cost for the treatment of heavy metal wastewater treatment. It also provided a new way for the agricultural wastes to reuse.