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 G ° 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.

Wetlands are important ecosystems with physical and economic benefits. However, many reports confirm the drastic loss of wetlands due to urbanisation and anthropogenic activities in many parts of the world. This study focused on the present-day state of wetlands in the Republic of South Africa. A meta-analysis was performed to elucidate the distribution and level of protection of selected wetlands. The classification of existing wetlands and the threat against wetlands were reported. Wetlands in South Africa are grossly endangered by human pollution, developmental activities, and invasive plants. From data obtained, about 47.89% of reported wetlands have a low level of protection and are thus susceptible to threats. The South African Department of Environmental Affairs protects most of the wetlands (28.17%) in the country. Major weaknesses identified for wetland degradation are the ignorance of people about the benefits of wetlands and the weak implementation of frameworks and policies that currently exist. The impact of legislations and policies on the preservation of wetlands is presented as well as the need for community education on environmental degradation. Therefore, the current state of several wetlands calls for urgent attention, and there is need for a strengthening of existing laws and policies in order to prevent wetland damage and extinction.