Adsorption of methylene blue from water by citric acid modified orange peel | 柠檬酸改性桔皮对水中甲基蓝的吸附

Chinese. 探讨柠檬酸改性对桔皮生物吸附剂吸附污染物能力的影响，为桔皮的资源利用提供新途径，为污水净化吸附剂的筛选提供理论依据。以粗桔皮(OP)为吸附剂原材料，以柠檬酸为改性剂，通过酯化反应制备出了改性桔皮吸附剂――柠檬酸改性桔皮（COP）和碱处理柠檬酸改性桔皮（MOP），以染料甲基蓝（MB）为污染物，采用恒温振荡处理法，考察了吸附剂用量、MB质量浓度、体系pH、温度等因素对OP、COP和MOP吸附MB能力的影响，并对其吸附动力学和热力学进行了探讨。3种吸附剂对MB的吸附能力与体系pH有关，当pH为2～10时， MOP对MB的吸附能力变化不大，而OP和COP对MB的吸附能力，在pH＞6以后才能达到吸附平衡。在相同温度条件下，3种吸附剂的最大吸附量依次表现为MOPOPCOP；在30 ℃时，OP、COP和MOP的最大吸附量可达112.45，27.59和189.92 mg/g。3种吸附剂对MB的吸附均可在120 min后达到吸附平衡，吸附动力学过程符合二级反应动力学模型，吸附热力学过程符合Langmuir模型，桔皮吸附剂对MB的吸附为吸热的自发熵增过程。柠檬酸改性并经碱液浸泡后的桔皮，对MB有良好的吸附能力，是一种具有潜在利用价值的污水处理生物质吸附剂。

English. The effects of citric acid modification on the pollutant adsorbed by orange peel sorbents were discussed. The crude orange peel (OP) was selected as raw sorbent material and was modified with citric acid to produce potentially sorbents, citric modified orange peel (COP) and basified citric modified orange peel (MOP). The dye methyl blue (MB) was chosen as the pollutant in the study. COP, MOP and OP were evaluated for their MB removal capacities from water by batch experiments. The effects of various experimental parameters (e.g., initial pH, MB mass concentration, sorbent dosage, temperature) were examined, and the adsorption kinetics and thermodynamics were also discussed. The ratio of MB sorbed on the 3 sorbents were controlled by the pH of the system. For the MOP sorbent, there was no significant change on the MB sorption when the pH stayed between 2-10.While the OP and COP sorbents reached the adsorption equilibrium when the pH was up to 6. Under the same temperature the order of maximum adsorption capacity was such as MOPOPCOP, and the maximum adsorption capacity was 112.45, 27.59 and 189.92 mg/g for the OP, COP and MOP respectively under 30 ℃. The isothermal fitted the Langmuir model and the adsorption processes followed the pseudo-second-order rate kinetics, and the adsorption equilibrium could be obtained in 120 minutes, and the overall adsorption process was endothermic and spontaneous. The basified citric modified orange peel was a potential sorbent which can be used in the wastewater treatment and absorb MB effectively.