Hazardous metal cations enter water through the natural geochemical route or from the industrial wastes. Their separation and removal can be achieved by adsorptive accumulation of the cations on a suitable adsorbent. In the present work, toxic Pb(II) ions are removed from water by accumulating it on the surface of natural zeolite in three different forms; one untreated and two treated samples, one sample treated with 2 M HCI solution and other is treated with 3 M NaOH solution. Natural zeolite is mainly composed of clinoptilolite, and mordenite, with amount of nonzeolite phase (smectite and illite) and C and CT opal. The adsorption experiments are carried out using a batch process in environments of different pH, initial Pb(II) concentration, interaction time and amount of zeolites. Treated zeolite samples show high exchange capacity for Pb(II) compared to untreated sample, however, acid-treated sample shows an exceedingly good exchange capacity. Equilibrium data fitted well with the Langmuir isotherm model with maximum adsorption capacity of 115, 126, and 132 mg g -1 of untreated natural zeolites, alkali-treated zeolites and acid-treated zeolites respectively. The rates of adsorption were found to confirm to pseudo-first order kinetic with good correlation and the overall rate of lead ions uptake.

No abstract

This study focuses on the assessment of surface soils from industrially polluted region (El Tebbin) of southern Cairo, Egypt. The impact of agricultural, residential and industrial land use on soils developed from Nile river sediments has significantly compromised their function. Previous evidence has shown that the food chain is contaminated and enhances risk of contaminant exposure of the residential communities. This study investigates factors controlling potentially toxic element (PTE) distribution (Co, Ni, Pb, Cd, Zn, Cr and Cu) in El Tebbin soils and provide estimates of their mobility and bioavailability. The PTE concentrations are characterised by high variability as result of the variety of natural and anthropogenic influences. Highest spatial variability is found for Zn, Cd, Pb and Cu (C.V = 260.0%, 280.4%, 140.8% and 159.6% respectively) and enrichment factors indicate strong anthropogenic inputs. For Co and Ni, relatively low spatial variability (C.V = 65.8% and 45.0% respectively) with depletion in Ni suggests a relatively minor contribution from anthropogenic sources. For Cr, a more uniform distribution pattern showing depletion to minimal enrichment across the study area (C.V = 19.2%) reflects almost exclusive lithogenic control. Using principle component analysis (PCA) to explore concentration data reveals that the major inputs affecting PTE distribution are modified by primary soil properties (texture and pH). Their relative bioavailability (identified through sequential chemical extraction) relates strongly to local input sources. Those elements dominated by lithogenic input (Ni and Co) were found predominantly in soil residual fractions (95.6% and 90.5% respectively), while elements with stronger anthropogenic contributions (Cd, Zn, Pb and Cu) showed much higher portion in the more mobile and bioavailable fractions obtained from sequential chemical extraction, with average proportions of the totals being 62.6%, 57%, 40.7% and 39.2% respectively. Those PTEs with strong anthropogenic influence are potentially much more mobile for bioaccumulation in food chain with increased health risk for exposed residents and are confirmed by elevated concentrations of Cd, Zn, Pb and Cu recorded in local plant species. The main pollution sources were further highlighted by cluster analysis and showed vehicle traffic and specific industrial activities but which varied significantly from site to site. The identification of sources through the approach developed here allows prioritisation of monitoring and regulatory decisions by the local government to reduce further environmental exposure of the local population.

No abstract

No abstract