| In recent years, the rapid economic development in our country results in therapidly increasing emissions of industral wastewater. In the21st century, water pollutionproblems have been deeply affected the survival and development of human beings.Using agriculture and forestry waste biomass to remove the pollutants in the wastewater,biosorption as a economic, efficient and environmental friendly water treatmenttechnology, has attracted people’s much attention. Camellia oleifera shell (COS) is aby-product from camellia oil industry and generally accounts for60%of the entire teafruit weight, COS are discarded or as a fuel generally after oiling lead to resourceutilization is very low. COS containing cellulose, hemicellulose, lignin and tannin(polyphenols), can be used as a biological adsorbent to deal with wastewater. Due to itsthe performance in wastewater treatment is not very good, therefore, this paper aims toimprove its adsorption ability for pollutants by modification of COS with differentmethods. The detail research contents are as follows:1. The adsorption of Crystal Violet(CV) on camellia oleifera shell (COS) wasstudied in this work. The parameters such as COS dose, initial CV concentration,adsorption time and pH, which were expected to have great effect on the CV adsorptionwere investigated. The results showed that98.01%of CV could be removed on theconditions that were0.30g of COS, pH=8.00, initial CV concentration50mg·L–1,adsorption time of3h and T=288K. The pseudo first order model, pseudo secondorder model and intraparticle diffusion model were used to describe the kinetic behavior,and it found that the kinetic data fitted well with the pseudo second order model. Whenthe initial CV concentration was40mg·L–1, the rate constant and the correlationcoefficient were0.0436L·mg–1min–1and0.9999, respectively. The adsorption isothermof CV fitted the Langmuir isotherm model well, and the adsorption capacity of CV onCOS increased with the increasing temperature in the tested range, and the correlationcoefficients were all above0.99. When the temperature was293K, the adsorptioncapacity was26.932mg·g–1. The thermodynamic calculation results indicated that theadsorption was a spontaneous and endothermic process accompanied with physicaladsorption. The regeneration experiment results found that the removal rate of CV wasmore than95%after the COS was regenerated seven times.2. The adsorbent was prepared by modifying camellia oleifera shell with citricacid(CA-COS) using the solid-phase esterifying technique in this work. The potential to remove crystal violet (CV) from aqueous solution was investigated through a series ofadsorption experiments. The influence of parameters like CA-COS dose, initial CVconcentration, solution pH, temperature, solution ionic strength, adsorption time on theremoval rate of CV on CA-COS were examined. Results showed that with the increaseof adsorbent dose, the removal rate of CV increased, and when the CA-COS dosage wasgreater than0.20g, the removal rate of CV increased rarely. The removal rate of CVdecreased with increasing initial CV concentration. The same concentration of CaCl2solution had greater effect on adsorption CV onto CA-COS than NaCl solution,however, when calcium ions concentration in the solution was0.2mol·L–1, removal rateof CV on CA-COS remained at around95%. The results showed that98.94%of CVcould be removed on the conditions that were0.20g of CA-COS, pH=7.00, initial CVconcentration150mg·L–1, adsorption time of5h at T=303K. Adsorption kineticsstudy found that the kinetic data fitted well with the pseudo second order model.Adsorption isotherm data of CA-COS adsorption CV more in line with the Langmuirmodel, the adsorption capacity was120.482mg·g–1at T=308K. The thermodynamiccalculation results indicated that the adsorption was a spontaneous and endothermicprocess. The regeneration experiment results found that the removal rate of CV wasmore than98%after the CA-COS was regenerated six times. The research resultsshowed that the CA-COS was a good adsorbent for removing CV in aqueous solution.3. The removal of heavy metal lead ions in aqueous solution by using citric acidmodified camellia oleifera shell(CA-COS) adsorbent was investigated in this work.Different experimental parameters were studied, such as adsorbent dosage, solution pH,concentration of lead ions, temperature, adsorption time, concentration of NaCl. Theresults showed that the optimal pH was range from4.5to5.5to remove Pb2+. WhenNaCl concentration was from0to0.20mol·L–1, removal rate of Pb2+reduced from88.34%to66.13%. The removal rate of Pb2+increased with the rising of temperature.The adsorption of Pb2+on CA-COS was a quick adsorption process, adsorption30mincould reach the adsorption equilibrium, the pseudo second order model could welldescribe adsorption kinetic experimental data of Pb2+, the correlation coefficient R2were1.000with different initial Pb2+concentrations. The adsorption of Pb2+fitted theLangmuir sorption isothermal model, the maximum adsorption capacities were45.167、48.239、49.652mg·g–1for the temperature were293,303,313K, respectively. Thethermodynamic study indicated that the sorption of Pb2+was spontaneous andendothermic process, higher temperature favored the sorption process. Regenerativeexperimental results showed that the CA-COS could reuse at least sevent times. 4. The adsorption of methyl orange on camellia oleifera shell modified by cationsurfactant hexadecyl trimethyl ammonium bromide(CTAB-COS) and its mechanismwere investigated. Examined the influence of many experimental factors on adsorptionof methyl orange, such as CTAB-COS dosage, solution pH, concentration of methylorange solution, temperature, adsorption time, solution ionic strength. The resultsshowed that the removal rate of methyl orange on CTAB-COS surface decreasedsignificantly with the increase in solution ionic strength, which suggested thatelectrostatic interaction between methyl orange anion and CTAB-COS was the majoradsorption mechanism. The removal rate of methyl orange on CTAB-COS decreasedwith the increase of solution pH value. Study found that the Zeta potential of COSchanged from negative value to positive after modifying with CTAB, and this indicatedthat the adsorption of cation surfactant on the surface of COS induced a change in itssurface charge properties. The increase in positive value of surface potential was themain reason for electrostatic adsorption of methyl orange on CTAB-COS. The resultsshowed that96.66%of methyl orange could be removed on the conditions that were0.40g CTAB-COS, pH=3.00, initial methyl orange concentration50mg·L–1,adsorption time of5h at T=288K. The pseudo second order model could welldescribe adsorption kinetic experimental data of methyl orange. The isotherm studyindicated that methyl orange adsorption on CTAB-COS could be fitted well with theLangmuir model other than Freundlich model, the maximum adsorption capacity formethyl orange at293K determined from the Langmuir isotherm was18.312mg·g–1.The thermodynamic analysis showed that the adsorption of methyl orange ontoCTAB-COS was a spontaneous and exothermic process. |
PDF Full Text Request