Conversion of solid waste to activated carbon to improve landfill sustainability

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.Landfills’ heterogeneous composites waste were evaluated as precursors for generation of activated carbon (AC). A single step chemical activation process was applied involving irradiation with microwave energy and impregnation with KOH. The average percentage yield of AC from active landfill precursor was higher than that from closed landfill for all depths sampled. Increase in impregnation ratio and irradiation power decreased the average percentage yield for both landfill precursors (Active: 38.1 to 33.1%) (Closed 42.1: to 33.3%). The optimum pH range for adsorption of methylene blue was pH 6-7, while adsorption increased with increase in temperature over the range 30 to 50oC. Carbonyl and hydroxyl groups were the major functional groups on the surface of AC. The properties of the AC are potentially suitable for the removal of cationic dyes and pollutants. AC generated from the landfill composite were comparable to that from some other biomass being managed through AC generation. This is the first report to demonstrate the possible reuse of landfill composite as AC. The reuse option of landfill composite could provide a means of sustainable management of landfilled municipal waste

Multivariate analysis of the effects of age, particle size and landfill depth on heavy metals pollution content of closed and active landfill precursors

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.Multivariate analysis of a heavy metal pollution survey of closed and active landfill precursors was carried out in order to compare environmental risk levels in relation to age, particle size and depth of the precursors. Landfill precursors (77) were collected and analyzed for 15 USEPA toxic heavy metals using ICP-MS. Heavy metals concentrations in closed landfill precursors were significantly higher than those in the active landfill for 11 of 15 heavy metals investigated (closed landfill order: Fe > Al > Mn > Cu > Pb > Ba> Co > Cr > Ni > Cd > As > Se > Ti). Cluster analysis and correlation studies indicated the distribution of the metals was more influenced by landfill precursor size than by depth of the sample. Principal component analysis (PCA) showed that 10 of 15 of heavy metals of both landfill precursors were from similar anthropogenic sources. Heavy metals pollution indices (Igeo > 5, EF > 40 and CF > 7) of both active and closed landfill precursors exceeded limits in the order of Zn > Cd > Pb > Cu > Ag, indicating a major potential health risk influenced by age and particle size of precursor. Zn, Cd, Cu and Pb of both landfill precursors exceeded the USEPA set standard for assessment of human health risk for each of the metals (1×10 -4 to 1× 10-3). This study highlights the need for the integration of a clean-up process for precursors from both types of landfill to reduce possible environmental pollution during a reuse process

Seasonal variations in moisture content and the distribution of total organic carbon in landfill composites: case of active and closed landfills in Lagos, Nigeria

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.The compositional trend and characteristics of active and closed landfill composites with depth was evaluated, in order to establish possible relationships between seasonal variations in moisture content, distribution of total organic carbon (TOC) and pH stability. A bulk system of composite classification was used. Both landfills had similar waste constituents, but varied widely in relation to the measured parameters. The TOC levels of the landfills were more influenced by the less degraded component than by the depth. Moisture content in both landfills had a positive significant statistical relationship with less degraded weight (P<0.01) and a negative relationship with more degraded weight (P<0.05), but was not significantly related to pH. These data suggest that seasonal variations and the less degraded component of samples are major factors influencing the moisture content and distribution of TOC in active and closed landfills, irrespective of difference in the disposal period of the waste into landfill

Comparative Characterisation of Closed and Active Landfill Composites Using EDX, FTIR and Proximate Techniques.

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.The elemental and chemical constituents of an active and a closed landfill were compared using Fourier transform - infrared (FTIR) spectroscopy, scanning electron microscope / energy-dispersive X-ray (SEM/EDX) spectroscopy, and proximate analysis. The two landfills had similar major elemental constituents representing 96.5% and 98.4% of elemental composition for the closed (O > C > Si> Fe > Ca >Al) and active(C > O > Si > Al > Ca > Fe) landfill samples respectively. The average concentration of Al was significantly higher (p=0.024) in the active landfill, while Ca was significantly higher (p=0.023) in the closed landfill. Cluster analysis revealed that similarities were more influenced by the level of composite degradation (more degraded / less degraded) than by depth or seasonal variations. Samples from both landfills showed FTIR absorption peaks that indicated mineralisation and stability of waste constituent. Active landfill samples showed distinguishing peaks at 3690 and 3619 cm-1 attributed to O-H vibration of clayey mineral (kaolin), while closed landfill samples were characterised by a carbonates peak at 873 cm-1. For both landfills, the average ash content (>51%) of the waste was above the level considered suitable for energy recovery from waste. These findings inform strategic decisions in management of the landfills and in the determination of possible alternative uses for landfill waste

Comparative characterization of closed and active landfill composites using spectroscopic and proximate techniques

INTRODUCTION: Effective utility of mixed waste in the landfills lies before its complete degradation rather than after landfill closure. The elemental and chemical constituents of an active and a closed landfill composite were compared using Fourier transform - infrared (FTIR) spectroscopy, scanning electron microscope / energy-dispersive X-ray (SEM/EDX) spectroscopy, and proximate analysis in order to determine potential alternative uses. METHOD: Landfill sites were systematically gridded into seven cells according to RCRA USEPA guidelines. Three samples were obtained from each cell at upper (0-15cm), mid (16-35cm) and low- (36-50cm) depths, both during the dry and wet seasons. The dried samples were separated by size into composites of less degraded (S> 0.63mm) and more degraded (S<0.63mm) components and homogenised. Proximate parameters (ash, volatile and fixed carbon) of samples were determined by ASTM D3174-5 methods. An Alpha attenuated total reflectance -FTIR spectrometer (Bruker) and X-Max SEM/EDX Instruments were used to evaluate the functional and elemental properties. RESULTS: both landfills had similar major elemental constituents representing 96.5% and 98.4% of elemental composition for the closed (O > C > Si> Fe > Ca >Al) and active(C > O > Si > Al > Ca > Fe) landfill samples. Cluster analysis revealed that elemental similarities were more influenced by the level of composite degradation (more degraded / less degraded) than by depth or seasonal variations. FTIR absorption peaks of both landfill samples indicated mineralised waste constituent with some distinguishing peaks peculiar to each landfill. The average ash content (>51%) of the waste in both landfills was above the level considered suitable for energy recovery from waste. DISCUSSION: The absence of major organic peaks precludes use of the waste for soil enrichment and anaerobic digestion feeds, but not for landfill covering. These findings, from rapid and amenable spectroscopic techniques, inform strategic management decisions for landfills

Microwave Acid Digestion Efficiency Of Landfill Composites Determined By ICP-MS Analysis

Microwave acid digestion of solid samples combined with inductively coupled plasma – mass spectrometry (ICP-MS) provides a viable approach to quantification of heavy metals within landfill waste. The efficiency of Aqua regia and HNO3 in microwave digestion of both closed and active landfill composites was compared, with a view to relating heavy metals distribution to the particle size of the landfill composites. Landfill sites were systematically gridded into seven cells according to RCRA USEPA guidelines. Three samples were obtained from each cell at upper (0-15cm), mid (16-35cm) and low- (36-50cm) depths. The particle size was determined using the sieving method and grouped as less degraded (S> 0.63mm) and more degraded (S<0.63mm) components and homogenised. Microwave digestion of samples was carried according to the EPA3052 method using a CEM MARS Xpress digester. An Agilent 7500 ICP-MS was used to determined metal concentrations in digested samples. For 77% of the eleven USEPA toxic heavy metals investigated, microwave digestion with Aqua regia resulted in higher concentration of metals than with HNO3. Extraction precision for both acids was within acceptable limit for more degraded samples (RPD10%) a higher burden of heavy metals in closed landfill samples than active landfill samples, except for Ag and Zn. The more degraded component of both landfills had elevated concentrations of heavy metals (>4% for HNO3 and >6% for Aqua regia). Sample recoveries based on CRM analysis showed that both acids were within the same accuracy (between 88% and 95%