Use of sweet ‘Pêra’ peel as an adsorbent in the treatment of textile effluents

ABSTRACT The disposal of industrial wastewater into aquatic bodies without proper treatment can cause severe damage to the environment and human health. The objective of this study was to perform the drying of the sweet orange (Citrus sinensis L. Osbeck) peel cultivar Pêra and evaluate the viability of its use as biosorbent in the removal of a direct dye. Drying was carried out in an oven with air circulation at temperatures of 60 and 80 ºC. The mathematical models of Page, Henderson and Pabis, Logarithmic, Midilli and Two-term exponential were fitted to the moisture data as a function of time. The material was characterized by scanning electron microscopy, point of zero charge, and infrared spectroscopy. In the adsorption study, a complete 24 factorial design was used to analyze the influence of mass, initial concentration, solution pH and contact time on adsorbed quantity (qt) and removal percentage of the dye (R%). In the drying, the two-term exponential model fitted best to the experimental data. The characterization of the material indicated that the adsorbent has zero charge point of 3.5 and porous structure, and the infrared analysis indicated the presence of carboxylic and hydroxyl groups. In the adsorption, the adsorbed quantity of the dye increased under conditions of lower pH and biosorbent mass and higher initial concentration and contact time. The removal percentage of dye increases with higher biosorbent mass. The biosorbent used is a promising waste for the adsorption of the burgundy-16 dye.

摘要 未经妥善处理的工业废水直接排入水生环境，会对生态环境与人类健康造成严重损害。本研究旨在对佩拉品种甜橙（Citrus sinensis L. Osbeck）果皮开展干燥处理，并评估其作为生物吸附剂（biosorbent）去除直接染料的应用可行性。干燥实验在鼓风循环烘箱中于60℃与80℃条件下进行。将Page模型、Henderson and Pabis模型、对数模型（Logarithmic）、Midilli模型以及双项指数模型（Two-term exponential）拟合至随时间变化的水分含量数据。采用扫描电子显微镜（Scanning Electron Microscopy）、零电荷点测试以及红外光谱法（Infrared Spectroscopy）对材料进行表征。吸附研究部分，采用全因子24实验设计，分析吸附剂投加量、初始染料浓度、溶液pH值及接触时间对吸附量（qt）与染料去除率（R%）的影响。干燥实验结果表明，双项指数模型对实验数据的拟合效果最佳。材料表征结果显示，该吸附剂的零电荷点为3.5，且具备多孔结构；红外光谱分析证实其表面存在羧基与羟基官能团。吸附实验结果表明，在较低pH值、较小吸附剂投加量、较高初始染料浓度以及更长接触时间的条件下，染料吸附量会显著提升；而染料去除率则随吸附剂投加量的增加而升高。本研究所用的生物吸附剂是一种极具应用潜力的废弃资源，可用于去除酒红-16（Burgundy-16）染料。