Edokpayi Joshua N, Ndlovu Stanley S, Odiyo John O
1Hydrology and Water Resources Department, University of Venda, Thohoyandou, 0950 South Africa.
2Ecology and Resource Management, University of Venda, Thohoyandou, 0950 South Africa.
BMC Chem. 2019 Jan 30;13(1):10. doi: 10.1186/s13065-019-0530-x. eCollection 2019 Dec.
Dyes are ranked as an important class of pollutants which affect the aesthetic property of the environment when present even in very low concentrations. This study was carried out to explore the potential use of an agricultural waste (Marula seed husk) to decontaminate methylene blue (MB) from aqueous solution. The effect of change in water chemistry was also examined. The influence of basic adsorption parameters such as contact time, temperature, dosage, pH and particle size on the efficiency of adsorption were investigated. Langmuir and Freundlich isotherms were used to describe the equilibrium data while Pseudo first, second order and Elovich kinetic models were used to evaluate the kinetics of the adsorption process. Thermodynamic parameters such as change in enthalpy (ΔH°), entropy (ΔS°) and Gibbs free energy (ΔG°) were evaluated. Natural surface water showed higher MB removal efficiency than de-ionized water. The sorption process was favored more in alkaline pH range (7-10). The dye adsorption process was found to be endothermic, while Δ° was negative implying that the reaction is spontaneous. Functional group analyses on the adsorbent showed the presence of hydroxyl, carbonyl and carboxyl groups. The Langmuir equilibrium model best described the adsorption process based on the linearized coefficient. The Pseudo second order model best described the kinetics of the reaction.
染料被列为一类重要的污染物，即使在浓度很低的情况下存在，也会影响环境的美观。本研究旨在探索利用农业废弃物（马鲁拉籽壳）从水溶液中去除亚甲基蓝（MB）的潜在用途。同时还研究了水化学变化的影响。考察了接触时间、温度、剂量、pH值和粒径等基本吸附参数对吸附效率的影响。用朗缪尔等温线和弗伦德利希等温线描述平衡数据，用拟一级、二级动力学模型和埃洛维奇动力学模型评估吸附过程的动力学。评估了焓变（ΔH°）、熵变（ΔS°）和吉布斯自由能（ΔG°）等热力学参数。天然地表水对MB的去除效率高于去离子水。吸附过程在碱性pH范围（7-10）更有利。发现染料吸附过程是吸热的，而Δ°为负，这意味着反应是自发的。对吸附剂的官能团分析表明存在羟基、羰基和羧基。基于线性化系数，朗缪尔平衡模型最能描述吸附过程。拟二级动力学模型最能描述反应动力学。
