Phosphorus recovery from a pilot-scale grate furnace: influencing factors beyond wet chemical leaching conditions

Phosphorus is a non-renewable resource going to exhaustion in the future. Sewage sludge ash is a promising secondary raw material due to its high phosphorus content. In this work, the distribution of 19 elements in bottom and cyclone ashes from pilot-scale grate furnace have been monitored to determine the suitability for the phosphorus acid extraction. Moreover, the influence of some parameters beyond wet chemical leaching conditions were investigated. Experimental results showed that bottom ash presented lower contamination in comparison to cyclone ash and low co-dissolution of heavy metals (especially Cr, Pb and Ni), while high phosphorus extraction efficiencies (76-86%) were achieved. High Al content in the bottom ash (9.4%) negatively affected the phosphorus extraction efficiency as well as loss on ignition, while the particle size reduction was necessary for ensuring a suitable contact surface. The typology of precipitating agents did not strongly affect the phosphorus precipitation, while pH was the key parameter. At pH 3.5-5, phosphorus precipitation efficiencies higher than 90% were achieved, with a mean phosphorus content in the recovered material equal to 16-17%, comparable to commercial fertilizers. Instead, the co-precipitation of Fe and Al had a detrimental effect on the recovered material, indicating the need for additional treatments

Implementing sustainability in laboratory activities: A case study on aluminum titanium nitride based thin film magnetron sputtering deposition onto commercial laminated steel

The goal of the study was to identify the environmental hotspots of an experimental research work at lab scale consisting in the physical vapor deposition magnetron sputtering of aluminum titanium nitride based thin coatings onto commercial laminated steel. The findings can provide useful insights for supporting the design of future experimental research campaigns, or instrumentation set-ups, with lower environmental impacts. Results highlighted that the main driver of impacts in the analyzed laboratory activities was the electricity used for instruments operations, in particular for the vacuum keeping. Thus, several optimization strategies were evaluated to reduce the overall electricity consumption, and to improve the environmental profile of experimental activities

A new breakthrough in the P recovery from sewage sludge ash by thermochemical processes

For the first time, the thermochemical treatment of sewage sludge ash made by using microwaves, associated with a devoted patented chamber, was realised. It promotes the formation of bioavailable CaNaPO4 compound, offering a new breakthrough in recovering phosphorus from sewage sludge ash and providing new possibilities in terms of sustainability

Assessment of a simple and replicable procedure for selective phosphorus recovery from sewage sludge ashes by wet chemical extraction and precipitation

The selective phosphorus recovery by wet chemical extraction and precipitation was assessed at the laboratory scale aiming at identifying a simple and replicable procedure that could be effectively applied to different types of sewage sludge ashes. The experimental work was performed on five samples of sewage sludge ashes, of which three were obtained from muffle-furnace incineration and two from full-scale mono-incineration plants. A single-step extraction procedure has been investigated by applying different operating conditions (type of leaching acid, liquid-to-solid ratio, contact time). Experimental results indicated that phosphorus recovery efficiency varied between 54 and 92% with limited co-dissolution of metals and metalloids, except for arsenic. Operating conditions, sewage sludge ashes characteristics and phosphorus removal processes in the wastewater treatment plant were the main factors affecting phosphorus recovery efficiency. The application of optimal operating conditions (0.2 M sulfuric acid, liquid-to-solid ratio of 20 and contact time of 2 h) resulted in phosphorus recovery from 76 to 92% on four samples. Subsequently, precipitation of phosphorus from acidic leachate was carried out by lime dosing. After filtering and drying, the recovered products presented a P2O5 content between 11.5 and 36.7% dry weight, with a fraction of soluble phosphorus between 75 and 91%, a good percentage for application as fertilizer or animal feed. Since few undesired elements (i.e., As, Cu and Zn) exceeded the limits for fertilizer application (exception was represented by Ni and Pb, which were present at low concentration), an additional purification step may be required. Overall, experimental results highlighted the influence of process parameters on phosphorus recovery

Impurities removal by laser blow-off from in-vacuum optical surfaces on RFX-mod experiment

An in situ window cleaning system by laser blow-off through optical fiber has been developed on the basis of a feasibility study previously presented. The beam generated by a Q-switched Nd:YAG laser is launched in a vacuum box into a high damage threshold optical fiber through a lens. The fiber output is focused on the impurities-coated surface of a vacuum window exposed to the plasma of the RFX-mod experiment, and it is remotely controlled with an xy motion system to scan the entire surface. We first investigate the energy density threshold necessary to ablate the deposited impurity substrate on removed dirty windows: above threshold, a single laser pulse recovers 3c95% of the window transmission before its exposure to the plasma, while below it the efficiency of the cleaning process is too poor. The system so conceived was then used to clean the three collection windows of the Main Thomson scattering diagnostic on RFX-mod. We also present results obtained applying the same technique to the SiO-protected Al mirror used for the Zeff diagnostic: an energy threshold for efficient impurity removal without mirror damage is first identified, then ablation tests are executed and analyzed in terms of recovered reflectivity. The SIMS technique is used both with windows and mirror to study the composition of surfaces before and after the ablation

Phosphorous and silica recovery from rice husk poultry litter ash: A sustainability analysis using a zero-waste approach

Phosphate rocks are a critical resource for the European Union, and alternative sources to assure the future production of a new generation of fertilizers are to be assessed. In this study, a statistical approach, combined with a sustainability evaluation for the recovery of materials from waste containing phosphorus (P), is presented. This work proposes a strategy to recover P and silica (SiO2) from rice husk poultry litter ash (RHPLA). The design of experiment (DoE) method was applied to maximize the P extraction using hydrochloric acid (HCl), with the aim to minimize the contamination that can occur by leachable heavy metals present in RHPLA, such as zinc (Zn). Two independent variables, the molar concentration of the acid, and the liquid-to-solid ratio (L/S) between the acid and RHPLA, were used in the experimental design to optimize the operating param-eters. The statistical analysis showed that a HCl concentration of 0.34 mol/L and an L/S ratio of 50 are the best conditions to recover P with low Zn contamination. Concerning the SiO2, its content in RHPLA is too low to consider the proposed recovery process as advantageous. However, based on our analysis, this process should be sustainable to recover SiO2 when its content in the starting materials is more than 80%

Safe core-satellite magneto-plasmonic nanostructures for efficient targeting and photothermal treatment of tumor cells

Magneto-plasmonic nanostructures functionalized with cell targeting units are of great interest for nanobiotechnology applications.</p

Safe core-satellite magneto-plasmonic nanostructures for efficient targeting and photothermal treatment of tumor cells

Magneto-plasmonic nanostructures functionalized with cell targeting units are interesting for nanobiotechnology applications. Photothermal treatment of cells targeted with antibody functionalized nanostructures and magnetically isolated, allows killing selected cells and is one of the applications of great interest. The magneto-plasmonic nanostructures here reported are synthesized with naked gold and magnetite nanoparticles obtained with a green approach based on laser ablation of bulk materials in water. The particles do not need purifications steps for biocompatibility and are functionalized with a SERRS (surface enhanced resonance Raman scattering) active molecule for detection and with an antibody for targeting tumor prostate cells. Quantitative results for the cell targeting and selection efficiency show, at picomolar concentrations, an overall accuracy of 94%. The photothermal treatment efficiently kill targeted and magneto-selected cells producing a viability below 5% after 3 minutes of irradiation compared with almost 100% viability of incubated and irradiated, but non targeted, cells