Acid mine drainage (AMD) is an industrial pollution of prime concern for the whole world. It is the driving force for an array of water pollutants especially heavy metals. Heavy metals (Cr, Mn, Fe, Ni, Co, Cu, Zn, Pb, Cd) were investigated in this study. Water and sediment samples were collected from the Ngwenya Iron Ore Mine Quarry Dam to investigate the occurrence of AMD phenomenon in the old mine. The main Fe compounds found in the Ngwenya Mine ore are haematite and pyrite. The Quarry Dam is located in one of the mine pits and it has neither visible inlet nor outlet. Physico-chemical parameters (pH, EC, ORP, T) were determined in the water by Electrochemical methods using the WTW 340i probes. Anions in the water were quantified by Ion Chromatography (IC) whereas heavy metals in water and sediments were quantified by Flame Atomic Absorption Spectrometry (FAAS). The BCR-Sequential Extraction procedure was used to speciate the heavy metals in the sediment samples. The mean pH of 4.34 in the Quarry Dam water is comparable to the pH of other AMD polluted water. The high mean EC of 4.522 mS/cm depicted that the water was laden with ions which are dissolved from the ore by the AMD. The sulfate ion, a well-known indicator for AMD pollution in water, is the second dominant anion where the order isThe heavy metal levels in water and sediments were in the order Co > Ni > Cr >Zn > Mn > Cu > Fe > Cd > Pb and Fe > Mn > Cr > Ni > Pb > Co > Cd > Cu > Zn respectively. The heavy metals are all bioavailable, hence they are potential health risks to both biota and residents in the vicinity of the mine. The pH of the water in the Quarry dam is comparable to those obtained for some other AMD polluted water. It is inferred that AMD is being produced in the old mine. It is recommended that an Environmental Impact Assessment of AMD must be carried out before the mine is re-opened.

Background Acid mine drainage (AMD) is a worldwide industrial pollution of grave concern. AMD pollutes both water sources and the environment at large with dissolved toxic metals which are detrimental to human health. This paper reports on the preparation of polymeric ion exchange resins decorated with hydrated iron oxides and their application for the ecological removal of toxic metals ions from AMD. Methods The hydrated iron oxide particles were incorporated within commercial chelating ion exchange resins using the precipitation method. The synthesised hybrid resins were then characterized using appropriate spectroscopic and solid-state techniques. The metal ion levels were measured using the inductively coupled plasma-optical emission spectrometer (ICP-OES). The optimization of contact time, pH, and adsorbent dosage were conducted to enhance the efficiency of adsorption of toxic metals onto the hybrid organic/inorganic nanosorbents. Kinetics and adsorption isotherms were constructed to study the adsorption mechanisms of the adsorbents. Results The results showed that the dispersed Fe-O is hydrated and amorphous within the hybrid materials. The adsorption kinetics followed the pseudo-second-order shown by the high R 2 values. The hybrid adsorbents were finally tested on environmental AMD samples and were able to remove toxic metals Al, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn at various removal degrees. Conclusion Solution pH played a crucial role in the adsorption of toxic metals on hybrid iron oxide adsorbents. The hybrid TP-260 HFO had higher affinity for toxic metals than other prepared adsorbents thus has a potential for acidic mine water pollution remediation. The adsorbed Al(III) can be recovered using NaCl-NaOH binary solution from the loaded resins.

Twenty-three water samples and three "yellow boy" samples were obtained from different water bodies located at the foot of the Ngwenya Mountain on top of which the old Ngwenya Iron Ore Mine is located. The samples were analysed for pH, electrical conductivity (EC), redox potential (ORP) and temperature (T). The dominant Fe species was determined using a UV-VIS spectrophotometer. Selected anions namely: halogens (F − , Br − , Cl −), the nutrients (2 NO − , 3 NO − , 4 PO 3−) and the best indicator for AMD pollution (4 SO 2−) were analysed using Ion Chromatography (IC) while the selected heavy metals, namely: Cr, Mn, Fe, Ni, Co, Cu, Zn, Pb and Cd were analysed using Flame Atomic Absorption Spectrometry (FAAS). The physico-chemical parameters ranges obtained were pH (6.32-8.63), EC (11.00-585.33 µS/cm), ORP (−93.67-79.33 mV) and T (7.60˚C-18.57˚C). The levels of the Fe species (ppm) in the water samples were Fe 2+ (0.56-3.17) and Fe 3+ (0.00-0.73). Measured mean anion ranges in ppm were F-(0.00-0.15), Cl − (1.5-11.19), 3 NO − (0-13.25) and 4 SO 2− (0.05-22.29). The mean ranges for the heavy metals in the water samples in mg/l were Cr (0.00-2.46), Mn (0.00-0.30), Fe (0.00-0.34), Ni (0.00-0.34), Co (0.00-0.29), Cu (0.00-0.07), and Cd ((0.01-0.11) whilst Zn and Pb were not detectible. The average pH in all the sites was within the acceptable range (6.5-8.5) according to WHO standards except for two sites. Fe 2+ was the dominant Fe species in the water samples. The water was free from anion pollution because all measured anion levels were below the guideline by WHO. The relative percentages of sites polluted by the respective heavy metals were: Cd (83%), Cr (71%), Ni (46%), Co (42%), Mn (17%), Fe (4%) while no site was polluted by Cu, Zn and Pb. The State needs to set up sound remediation strategies to save the populations around the Ngwenya Mine from the heavy metal pollution they are exposed to by using water polluted by the mining activities.

Environmental pollution due to acid mine drainage (AMD) is a worldwide concern because of its high content of toxic metals and acidity. The toxic metal species present in AMD tends to affect negatively the whole ecological system where it is discharged, and this requires an elective solution to remedy the environment. In this study, hydrated ZrO 2 nanoparticles (HZO) were irreversibly dispersed within chelating ion-exchange resins using the precipitation method, resulting in HZO-260, HZO-207, HZO-214, HZO-4195 and HZO-900 organic/inorganic nanosorbents which were used for the removal of metals from AMD. The synthesized nanosorbents were characterized using SEM-EDS, FTIR and XRD. The effect of time, adsorbent dosage and pH on Al(III) adsorption was investigated using the batch technique. The SEM-EDS confirmed the incorporation of HZO within all the parent resins, while XRD showed that the hybrid materials were amorphous. The adsorption of Al(III) occurred through physisorption and was favourable only onto HZO-260 as revealed by the data modelling. Metal levels were determined using the ICP-OES technique. The HZO-260 removed 100% Al(III) in acidic conditions and was successfully regenerated for reuse using a NaCl-NaOH binary solution (pH > 12). HZO-260 removed selected metals (Al, Cr, Mn, Fe, Ni, Co, Cu, Zn, Pb and Cd) from environmental AMD. Therefore, HZO-260 has a promising potential as an adsorbent for AMD remediation.

Fe, Zr and Ti oxides nanoparticles were each embedded onto a weak acid chelating resin for support, by the precipitation method, to generate three hybrid adsorbents of hydrated Fe oxide (HFO-P), hydrated Zr oxide (HZO-P) and hydrated Ti oxide (HTO-P). This paper reports on the characterization, performance and potential of these generated nanoadsorbents in the removal of toxic metal ions from acid mine drainage (AMD). The optimum contact time, adsorbent dose and pH for Al(III) adsorption were established using the batch equilibrium technique. The metal levels were measured using the inductively coupled plasma-optical emission spectrometer (ICP-OES). The SEM-EDS results confirmed the presence of the metal oxides within the hybrid resin beads. HFO-P, HZO-P and HTO-P adsorbed Al(III) rapidly from synthetic water with maximum adsorption capacities of 54.04, 58.36 and 40.10 mg/g, respectively at initial pH 1.80 ± 0.02. The adsorption of Al(III) is of the second-order in nature (R2 > 0.98). The nanosorbents removed 10 selected metals from environmental AMD and the metal removal efficiency was in the order HTO-P > HZO-P > HFO-P. All three hybrid nanosorbents can be used to remove metals from AMD; the choice would be dependent on the pH of the water to be treated.