Adsorption and recovery of phosphate from aqueous solution by the construction and demolition wastes sludge and its potential use as phosphate-based fertiliser

This study aimed to investigate phosphate removal from aqueous effluents by an inorganic sludge from the inert part of construction and demolition wastes (CSW) as adsorbent. It is also discussed the application of the loaded P adsorbent as potential fertiliser. The CSW was also thermally treated at 800¿°C for 2¿h (CSW-T), and its influence in the P removal was also investigated. The characterisation techniques highlighted low porosity on CSW and CSW-T adsorbents and that they are mainly formed by oxides which could enhance the P uptake and recovery. In pH experiments, P adsorption increased as initial pH increased, at pH higher than 7.8 the P removal sharply increased due to the formation of calcium phosphate precipitate. The mechanism of the P adsorption onto CSW indicated that the process was mainly controlled by chemical bonding or chemisorption. The results showed that CSW-T was more effective for P removal in comparison to CSW based on the Liu isotherm, the maximum sorption capacity attained was 24.04 (CSW) and 57.64¿mg¿g-1 (CSW-T). Based on the Avrami’s kinetic models, the time for attaining 95% of saturation was 212.6 (CSW), and 136.6¿min (CSW-T). CSW and CSW-T showed the highest phosphate-removal performance among many adsorbents found in the literature; therefore, this kind of waste can be used widely as an inexpensive phosphate-recovery adsorbent. Besides, the P loaded adsorbents could be used as potential fertilisers which could be an interesting and efficient way of reuse for this waste.Peer ReviewedPostprint (published version

Utilização de jigues a ar na concentração de resíduos de construção e demolição

Resíduos de construção e demolição são um dos principais resíduos sólidos gerados em centros urbanos em todo o mundo. Normalmente, parte deles são utilizados, após cominuição e classificação granulométrica, sem nenhum processo de separação ou concentração. Eles podem ser usados como agregados em concreto de baixa resistência, em sub-bases de estradas, ou em outras utilizações com baixo valor agregado. O presente trabalho apresenta estudos de separação e concentração em jigues a ar dos diferentes materiais presentes nestes resíduos.Peer ReviewedObjectius de Desenvolupament Sostenible::9 - Indústria, Innovació i InfraestructuraPostprint (published version

Coupling of attrition and accelerated carbonation for CO2 sequestration in recycled concrete aggregates

Peer ReviewedObjectius de Desenvolupament Sostenible::7 - Energia Assequible i No ContaminantPostprint (published version

Concentração de resíduos de construção e demolição por sensor-based sorting

Os Resíduos de Construção e Demolição (RCD) apresentam composições diferentes, dependendo da construção do prédio, tamanho da cidade, desenvolvimento do país etc. Os principais componentes do RCD são o concreto e a cerâmica vermelha (tijolos). Este estudo mostra a possibilidade de separar e concentrar RCD através de Separadores Baseados em Sensores (Sensor-based sorting). Em todos os testes foi utilizada uma mistura de concreto, cerâmica vermelha e gesso, sem a presença de metais ou impurezas leves. Partículas de concreto e cerâmica vermelha foram escolhidas devido ao seu domínio em todos os RCD gerados. Partículas de gesso foram utilizadas devido a este ser o principal e mais prejudicial contaminante em formulações de novos concretos, bem como a possibilidade de reciclagem na indústria. Todos os testes foram realizados com partículas na faixa de tamanho de 20x4 mm.Peer ReviewedObjectius de Desenvolupament Sostenible::9 - Indústria, Innovació i InfraestructuraPostprint (published version

Fabrication, microstructure, and properties of fired clay bricks using construction and demolition waste sludge as the main additive

Green routes to prepare or manufacture sustainable building materials have been attracting much attention over the years targeting sustainability issues. In this investigation, for the first time, sludge from the inert mineral part of the construction and demolition waste (RA-S) is used as a primary raw material in the fabrication of fired bricks for building purposes. Fired bricks fabricated with different dosages of RA-S and earth material (i.e., 0%, 30%, 50%, 70%, and 100% by weight) were prepared and evaluated in terms of their physical-chemical properties. The RA-S was characterized, and the results showed that it could be classified as a clayey material and richly graded silty sand according to the French Standards. XRD analysis revealed that the addition of the RA sludge into raw earth material provoked changes slightly in the fired bricks. The compressive strength (CS) results indicated that the CS of the fired bricks increased with the addition of the RA-S from 30% to 70%. The highest CS was attained at the firing temperature of 800 °C. The density of the fired brick slightly reduced with the RA-S addition. The thermal conductivity results suggest that RA-S has better insulation properties compared to earth material. The RA-S sludge can be used in combination with earth material to fabricate fired bricks, which can meet the requirements of many Standards all over the World. In the light of these results, it is possible to say that the RA-S generated from recycling inert mineral part of construction and demolition waste plant is an excellent raw material to prepare efficient fired bricks that can be successfully employed in the real construction sector. Also, the highlighted results suggest that brickwork factories have the opportunity to improve production quality while significantly reducing manufacturing time, energy consumption, resource depletion, and environmental impact.The authors are also grateful to the Council for the Development of Higher Education at Graduate Level, Brazil (CAPES) for the postdoctoral scholarship granted through the National Postdoctoral Program (PNPD). The authors also thank Mr. Ferro, president of Esterel Terassement, for financial support and for providing the RA-S samples. Dr. Simoes dos Reis gives a special thanks to the cooperation opportunity between UFRGS and IFSTTAR through his Post-doctoral studies provided by PNPD. E.C. Lima thanks to Foundation for Research Support of the State of Rio Grande do Sul (FAPERGS), and National Council for Scientific and Technological Development (CNPq, Brazil) for financial support and sponsorship.Peer ReviewedPostprint (author's final draft

Production of high-quality coarse recycled aggregates through a two-stage jigging process

Peer ReviewedObjectius de Desenvolupament Sostenible::9 - Indústria, Innovació i InfraestructuraObjectius de Desenvolupament Sostenible::9 - Indústria, Innovació i Infraestructura::9.4 - Per a 2030, modernitzar les infraestructures i reconvertir les indústries perquè siguin sostenibles, usant els recursos amb més eficàcia i promovent l’adopció de tecnologies i processos industrials nets i racionals ambiental­ment, i aconseguint que tots els països adoptin mesures d’acord amb les capacitats respectivesObjectius de Desenvolupament Sostenible::12 - Producció i Consum ResponsablesObjectius de Desenvolupament Sostenible::12 - Producció i Consum Responsables::12.5 - Per a 2030, disminuir de manera substancial la generació de residus mitjançant polítiques de prevenció, reducció, reciclatge i reutilitzacióPostprint (published version

Characterization of Demolished Concretes with Three Different Strengths for Recycling as Coarse Aggregate

This paper presents a physical characterization for the recycling into new concretes of three comminuted concretes: C16/20 (“ordinary concrete”), C50/60 (“high strength concrete”), and C70/85 (“very high strength concrete”). The top size of the crushed concretes was 19.1 mm and the size range was 4.75 to 19.1 mm. The characterization was carried out with coarse aggregate liberation, to be prepared and concentrated in a gravity concentration process. The density distribution of the coarse aggregate, cement paste, and sand was carried out in different size ranges (4.75/19.1 mm; 4.75/8.0 mm; 8.0/12.5 mm; and 12.5/19.1 mm) for the three concretes studied. The form factor of the samples, as well as the porosity determination of particles in different density ranges, are presented. The obtained results indicate that the coarse aggregate liberation was more intensive for the low resistance concrete (C16/20), but a reasonable coarse aggregate recovery is possible for all concretes

Effect of concrete carbonation on phosphate removal through adsorption process and its potential application as fertilizer

© 2020. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/Concrete slurry is an abundant, cheap, and commonly found waste all over the world where construction activities take place; concrete slurry, which is rich in calcium and metallic oxides, could be successfully employed in the phosphate (P) removal from aqueous media. For the first time, the effect of the carbonation process on concrete adsorbent properties and how it can influence on the removal of phosphate ions in aqueous media are studied. Besides, the potential applicability of P loaded concrete adsorbent is also evaluated. The results showed that a non-carbonated sample was more effective in the P removal, due to higher releasing of calcium (Ca2+) in comparison to carbonated sample. The dissolved Ca2+ from the dissolution of calcium hydroxide (Ca(OH)2), calcium carbonate (CaCO3), and calcium oxide (CaO) are preferably precipitated by phosphates in high pH solution, reflecting in a high initial adsorption rate. General order kinetic and Liu isotherm provided better-fitting models for the adsorption behavior of P onto both non-carbonated and carbonated concrete samples. Phosphate removal was mainly ruled by chemical adsorption through inner-sphere complexation and P precipitation on the surface of the adsorbent containing Ca2+ as an essential ion in the adsorption mechanism. Compared with other phosphate adsorbents, both non-carbonated and carbonated concrete showed to be economical and efficient adsorbent. The non-carbonated sample gave a high adsorption capacity of P (47.6 mg g-1) and presenting fast and high initial adsorption, reaching 72% of P removal within 5 min (min) at 22 °C, while carbonated showed adsorption capacity of 30.6 mg g-1, at the same experimental conditions. Therefore, concrete slurries can be used widely as an inexpensive phosphate-recovery adsorbent. Besides, the application of these P loaded waste as potential fertilizers in soil can be an exciting and environmentally approach for reusing this solid-waste. The environmental analysis highlighted that the adsorbents did not leach out chemicals above the allowable limits, preconized by The Food and Agriculture Organization of the United Nations (FAO) for irrigation waters. However, aspects related to monitoring the presence and mobility of heavy metals on soil must be better addressed and monitored.Peer ReviewedPostprint (author's final draft

Demolished concretes recycling by the use of pneumatic jigs

Sampaio, C.H. et al., Demolished concretes recycling by the use of pneumatic jigs, Waste management and research, 38 (4) pp. 392-399. Copyright © 2020. DOI: 10.1177/0734242X20902835.Large quantities of construction and demolition waste is generated annually around the world. Part of this material is processed in recycling plants. After removing metals, fines and lights, the construction and demolition waste is crushed and sized and can be used as aggregates for low resistance concrete, for road sub-base, city landfill and other low value-added applications. For their use as coarse aggregate in structural concretes, construction and demolition waste must exhibit high densities and regularity of the material. This material usually is presented in demolished concretes. About 20% of the particles from demolished concretes can be used as coarse aggregates substituting part of natural aggregates in structural concretes. This article presents studies of demolished concretes recycling by the use of a pneumatic jig. All jigging tests were carried out with three different concretes produced in three strength classes: C16/20, ordinary concrete; C50/60, high strength concrete; and C70/85, very high strength concrete. Based on density distribution of the three concretes, there are reasonable masses with densities over 2.7¿g¿cm-3, particle density considered appropriate to the used as coarse aggregate for structural concretes. The concretes present different mass recoveries of the denser particles (different liberation). Coarse aggregates can be recovered with reasonable masses by the use of air jigs: About 65% for high strength concretes and about 75% for the low strength concrete. The jigging concentration efficiency depends on the concrete liberation, density and size distribution.The authors would like to thank the Brazilian National Council for Scientific and Technological Development (CNPq) for financial support. We are also very thankful to NORIE (Núcleo Orientado para a Inovação da Edificação), LEME (Laboratório de Ensaios Estruturais) and LEAMET (Laboratório de Estudos Ambientais para Metalurgia), research groups of the Federal University of Rio Grande do Sul, Brazil, where production and characterization of the concrete samples were carried out.Peer Reviewe