Production of zeolitic concentrates from WTP sludge

• Grant number: 23/02665-1
• Support Opportunities: Scholarships in Brazil - Master
• Start date: April 01, 2023
• End date: February 28, 2025
• Field of knowledge: Physical Sciences and Mathematics - Chemistry
• Agreement: SABESP
• Principal Investigator: Cauê Ribeiro de Oliveira
• Grantee: Thais Beatriz Miqueleti de Sena
• Host Institution: Embrapa Instrumentação Agropecuária. Empresa Brasileira de Pesquisa Agropecuária (EMBRAPA). Ministério da Agricultura, Pecuária e Abastecimento (Brasil). São Carlos , SP, Brazil
• Company: Ministério da Agricultura, Pecuária e Abastecimento (Brasil). Empresa Brasileira de Pesquisa Agropecuária (EMBRAPA). Embrapa Instrumentação Agropecuária
• Associated research grant: 20/12210-3 - Development of technological alternatives for the use of ETA sludge as raw material for the production of controlled release fertilizers, AP.PITE

Abstract

This project will have as main objective to define the necessary conditions for the synthesis of zeolite concentrates using selected sludge from ETAs as starting material. Initially, representative samples of WTP sludge will be requested from SABESP, collected in different periods of the year and in stations considered as a model by the company, to assess the variability of the residue. Up to 10 samples must be selected in contact with SABESP, seeking to limit the compositional universe to a representative range that may, in the future, facilitate the scaling of concentrate production. To correct the stoichiometry favorable for the precipitation of zeolites (1:1 mol Si:Al) mixtures can be made between sludge from different sources or corrections with a common Si source (quartz sand). If the Si:Al ratio is greater than 1 (excess of Si), no correction will be made considering that all Al should precipitate, leaving residual quartz. Residual Fe (salts and oxides) will not be considered in the synthesis, assuming that in the alkaline medium these will precipitate as hematite (Fe2O3), less critical for immobilization of phosphates than salts and aluminum compounds (e.g. boehmite, AlOOH or other transition aluminas). From these samples, zeolitic concentrates will be synthesized by the method of direct digestion of the waste with stoichiometry adjusted in KOH 3 to 5 mol.L-1, in slow stirring at temperatures between 70 and 90oC and aging periods of 24 to 48 h. The addition of finely ground zeolites (chabazite or clinoptilolite) can be made to act as a crystallization germ. Given the cost limitation of application, subsequent crystallization steps (hydrothermalization) will not be carried out, however, depending on the efficiency of the process, crystallization in an autoclave at temperatures from 100 to 150oC/24 hours for 24 to 48 hours will be tested in the laboratory to evaluate the potential gain in the total time of synthesis. These conditions have already tested at Embrapa Instrumentation for the synthesis of zeolitefaujasite1 and ZSM-5.2. It is important to emphasize that the activity will seek the production route with the lowest number of unit operations, being unnecessary to wash the precipitated gel, since the excess KOH will have a fertilizer function. The KOH concentration will be optimized during the synthesis process to minimize consumption, aiming at controlling the basicity of the final product. The final product should be a mixture of zeolites and other mineral phases, which will be evaluated by standard characterization techniques (mineralogical analysis by X-ray diffraction, chemical analysis by flame absorption, morphological evaluation by scanning electron microscopy, surface area analysis and pore volume by N2 physisorption, cation exchange capacity by titration, among other techniques available at Embrapa Instrumentation). An important aspect is the effective immobilization of Al in the zeolite structure, which will be evaluated by chemical analysis of the reaction medium after centrifugation and by incubation test in soils. The materials will be homogenized in a soil (to be chosen) mixed with a phosphate fertilizer(e.g. MAP), keeping the mixture in incubation at controlled temperature and humidity for periods of up to 48 days. The analysis of phosphorus exchangeable by resin, after this period, will indicate whether in fact the production process of the zeolite concentrate reduced the phosphorus immobilization capacity, from the comparison with the control negative (without fertilizer and without concentrate) and positive (with fertilizer and without concentrate). Variations in the test can be made, to show that the ETA sludge after treatment does not have appreciable phosphorus immobilization effects. (AU)

Scientific publications

(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)

MACHADO, RAQUEL CARDOSO.; VALLE, STELLA FORTUNA DO; SENA, THAIS BEATRIZ MIQUELETI; PERRONY, PAUL ESTEBAN PHEREZ; BETTIOL, WAGNER; RIBEIRO, CAUE. Aluminosilicate and zeolitic materials synthesis using alum sludge from water treatment plants: Challenges and perspectives. WASTE MANAGEMENT, v. 186, p. 15-pg., 2024-06-13. (22/09773-1, 20/12210-3, 23/02665-1, 23/01549-8)