Search results for "Waste"
showing 10 items of 2580 documents
Cadmium and Zinc Adsorption onto Activated Carbon: Influence of Temperature, pH and Metal/Carbon Ratio
1996
The adsorption characteristics of cadmium and zinc onto a granular activated carbon were studied. Cadmium and zinc removals increased on raising pH and temperature, and decreased on raising the molar metal/carbon ratio. The adsorption processes were modelled using the surface complex formation (SCF) Triple Layer Model (TLM) with an overall bidentate species. A dependence of the SCF constant on pH, the molar metal/carbon ratio and temperature was observed, and a correlation for log K ads was determined. The SCF model successfully predicted cadmium and zinc removals.
Mineralogy and geochemistry of Terra Rossa soils, western Sicily: insights into heavy metal fractionation and mobility
1996
Abstract The distribution of heavy metals in typical Terra Rossa soils and their partitioning in specific soil phases are estimated on the basis of the comparative evaluation of bulk contents, results from sequential chemical extraction procedure (SEP) and scanning electron microscopy/energy dispersive X-ray analysis ( SEM EDX ). A general natural enrichment of heavy metals with respect to average soil is observed. Cadmium proves to be remarkably high (up to 2.4 ppm). Large amounts of Fe, Cr, Cu, Ni, Pb, and Zn occur in the ‘residual’ fraction. The results indicate selective accumulation of the heavy metals in Fe oxides, present as hematite, goethite and maghemite. There is good evidence th…
Effect of pH, cation concentration and sorbent concentration on cadmium and copper removal by a granular activated carbon
1999
The single adsorption of cadmium and copper from aqueous solutions has been investigated on Darco 12-20 mesh granular activated carbon for a wide range of experimental conditions: pH, metal concentration and carbon concentration. The results showed the efficiency of the activated carbon as sorbent for both metals. Metal removal increases on raising pH and carbon concentration, and decreases on raising the initial metal concentration. The adsorption processes have been modelled using the surface complex formation (SCF) Triple Layer Model (TLM) with a single surface bidentate species or with an overall surface species with fractional stoichiometry. Bidentate stoichiometry considering pH, meta…
Cadmium Recovery from Spent Ni-Cd Batteries: A Brief Review
2021
The significant increase in the demand for efficient electric energy storage during the past decade has promoted an increase in the production and use of Cd-containing batteries. On the one hand, the amount of toxic Cd-containing used batteries is growing, while on the other hand, Cd is on a list of critical raw materials (for Europe). Both of these factors call for the development of effective technology for Cd recovery from spent batteries. The present paper is aimed at providing a short review of the recent progress in Cd recovery from spent batteries. Statistical data from the past decade on the source of Cd, its global production, and Ni-Cd battery recycling are given in the introducti…
Influence of humic acid on neptunium(V) sorption and diffusion in Opalinus Clay
2013
SummaryThe influence of14C-labeled M42 humic acid (HA) on the interaction between neptunium(V) and natural clay rock (Opalinus Clay (OPA), Switzerland) has been investigated in batch sorption and diffusion experiments under ambient air conditions. The effect of 10 mg/L HA on the diffusion of 8 μM Np(V) in OPA has been investigated in synthetic OPA pore water (pH 7.6, I = 0.4M) for the first time. Batch sorption experiments as a function of solid-to-liquid ratio (4-20 g/L) were performed under same experimental conditions to compare distribution coefficients obtained from both diffusion and sorption experiments. These experiments showed only a slight influence of HA on Np(V) uptake by OPA in…
Calcium phosphate precipitation in a SBR operated for EBPR: interactions with the biological process.
2008
The aim of this paper is to study the precipitation process in a sequencing batch reactor (SBR) operated for EBPR (enhanced biological phosphorus removal) and the possible effects of this phosphorus precipitation in the biological process. Four experiments were carried out under different influent calcium concentration. The experimental results and the equilibrium study, based on the Saturation Index calculation, confirm that the process controlling the calcium behaviour in a SBR operated for EBPR is the calcium phosphate precipitation. This precipitation takes place at two stages initially precipitation of the ACP and later crystallization of HAP. Also the accumulation of phosphorus precip…
Phosphorus recovery by struvite crystallization in WWTPs: Influence of the sludge treatment line operation
2010
Phosphorus recovery by struvite (MgNH(4)PO(4).6H(2)O) crystallization is one of the most widely recommended technologies for treating sludge digester liquors especially in wastewater treatments plants (WWTP) with enhanced biological phosphorus removal (EBPR). In this paper, phosphorus recovery by struvite crystallization is assessed using the rejected liquors resulting from four different operational strategies of the sludge treatment line. Phosphorus precipitation and recovery efficiencies of between 80-90% and 70-85%, respectively, were achieved in the four experiments. The precipitates formed were mainly struvite, followed by amorphous calcium phosphate and, in some experiments, by calci…
Calibration and validation of activated sludge model No.2d for Spanish municipal wastewater.
2002
Activated Sludge Model No. 2d (ASM2d) was validated with data obtained from pilot scale plant treating municipal wastewater from the city of Valencia (Spain). First of all, ASM2d was calibrated using experimental data from anaerobic, anoxic and aerobic batches. A set of kinetic and stoichiometric parameters resulted from these assays. Differences between the values obtained and default values proposed in ASM2d can be explained by the presence of glycogen accumulating organisms (GAOs). The calibrated model was then used to simulate results from a pilot plant. Simulation using the set of parameters obtained accurately reproduces experimental results. This paper also presents a detailed proced…
Mathematical protocols for calibration of wastewater treatment models
2015
Activated sludge models can be very useful for designing and managing wastewater treatment plants (WWTPs). However, as with every model, they need to be calibrated for correct and reliable application. Activated sludge model calibration is still a crucial point that needs appropriate guidance. Indeed, although calibration protocols have been developed, the model calibration still represents the main bottleneck to modelling. This abstract shows a procedure for the calibration of an activated sludge model based on a comprehensive sensitivity analysis and a novel step-wise Monte Carlo-based calibration of the subset of influential parameters. The key point of the step-wise procedure is that ca…
Nitrogen and phosphorus budgets in experimental grasslands of variable diversity.
2007
Previous research has shown that plant diversity influences N and P cycles. However, the effect of plant diversity on complete ecosystem N and P budgets has not yet been assessed. For 20 plots of artificially established grassland mixtures differing in plant diversity, we determined N and P inputs by bulk and dry deposition and N and P losses by mowing (and subsequent removal of the biomass) and leaching from April 2003 to March 2004. Total deposition of N and P was 2.3 +/- 0.1 and 0.2 +/- 0.01 g m(-2) yr(-1), respectively. Mowing was the main N and P loss. The net N and P budgets were negative (-6.3 +/- 1.1 g N and -1.9 +/- 0.2 g P m(-2) yr(-1)). For N, this included a conservative estimat…