Removal of Lead Ions From Aqueous Solutions Using Melamine-Modified Nano Graphene Oxide

Today, due to the industrialization of societies, the existence of heavy metals has created many problems for humans, other organisms, and the environment. Lead (Pb) is highly toxic and the second most commonly used metal. The aim of this study was to evaluate the efficiency of melamine-modified nanographene oxide in the removal of Pb from aqueous media. To increase the efficiency of graphene oxide, it was mechanically converted to nano graphene oxide and melamine (4, 2 and 6-triazine, 3, 1 and 5 triamine). Experiments were performed at pH value of 3-8, temperature of 15-50°C, Pb concentration of 5-200 mg/g, adsorbent dose of 0.01-0.06 g, and contact time of 15- 150 minutes. The mechanism of the adsorption process was investigated using two Langmuir and Freundlich isotherm models, pseudo-first order and pseudo-second order kinetic equations, and thermodynamic equations. The results showed that the adsorption rate corresponds to the Freundlich isotherm model and pseudo-second order kinetic equation. Thermodynamic studies also showed that the adsorption process is associated with increasing irregularities and it is endothermic. In constant conditions (pH of 6, contact time of 60 minutes, ambient temperature of 22°C, Pb concentration of 20 mg/L, and adsorbent dose of 0.01 g), the adsorption capacity was 191.65 mg/g. The highest adsorption occurs at the concentration of 5 mg/L and the highest adsorption capacity and removal percentage was observed at a concentration of 200 mg/L, which were 1896.3 mg/g and 98.8%, respectively. Due to the high adsorption capacity, the adsorbent was able to remove lead from the contaminated environment.

Heavy Metal Contamination in Drinking Water Supplies in the Villages of Divandarreh: The Use of Geographic Information System

One of the important aspects of drinking water pollution is the presence of heavy metals that can create hazards for consumer’s health. This study was performed to find the concentration of heavy metals (arsenic, lead, iron, and zinc) in drinking water sources of Divandarreh in Kurdistan province and prepare its zoning map. A total of 99 wells, springs, and reservoirs were selected for sampling in 78 rural areas of Divandarreh County. Samples were collected from each source using grab sampling methods in two phases (rainy and dry seasons). To find the concentration of lead, the atomic absorption device (VARIAN 240 AA) was used, and Inductively Coupled Plasma (ICP: VARIAN 710) was used for determining the concentration of arsenic, iron, and zinc. Analysis of data was done using SPSS version 22.0 and the analysis of spatial variability and estimation of the concentration of heavy metals (preparation of zoning map) in the study area were carried out by ArcGIS software. The average concentrations of arsenic, lead, iron, and zinc in dry and rainy seasons were 1, 0.6, 62.9, 31.4, and 0.13, 2.16, 11.5, 19.8, respectively. Zinc, iron, and lead concentrations in sample No. 36 were higher than the standard level; therefore, it can be inferred that these three elements can create health problems in the future.