Abstract The foundry industry generates large amounts of residual byproducts, such as waste foundry sand (WFS). This high generation has motivated studies concerning the disposition of WFS, which in turn can be used for road subbases. Nevertheless, paving applications are still limited, especially regarding the behavior of WFS when added to a mixture of crushed materials. Hence, the objective of this study was to evaluate WFS reuse in mixtures with crushed materials, applied as granular layers of granulometric stabilized pavements. The crushed materials and WFS were characterized by size distribution, physical aspects, and different mixtures, and later submitted to mechanical testing. Initial tests were utilized to define mixtures (crushed material + WFS) that fulfilled the technical requirements for road subbases. California bearing ratio and resilient modulus tests indicated that WFS additions up to 12% for “A” grading improved the bearing capacity of the mixture; while in “E” grading, WFS additions up to 38% resulted in no expressive improvement in bearing characteristics. Thus, for both gradings, a structure with high density, strength, and low susceptibility to deformations can be used for road subbase construction without technical issues. Finally, the highest WFS content (38%) mixture was environmentally classified as a Class II A non-inert waste, indicating its environmental viability for road applications.

ABSTRACT The paper processing industry is characterized as one of the three largest producers of wastewater of significant environmental contamination. In order to minimize impacts on water resources and comply with the standards required by legislation, advanced treatment solutions are needed. The present study developed a ceramic microfiltration membrane based on 60% of rice husk ash waste and 40% of kaolinitic clay to pretreat a raw effluent of paper industries. The membrane was obtained by uniaxial compression (27MPa) in an electric press, with subsequent sintering at 1,220°C for 1 hour. Base formulation materials were characterized by chemical and physical analyses. The membrane presented apparent porosity of 34.59%, density of 1,30 g.cm-3, diameter and thickness linear retraction of 1.7 and 2.5%, respectively, fire loss of 9.3% and a good chemical stability at acid and base solution. Hydraulic permeability corresponded to 11.3 × 10-3 m3/m2 s MPa-1, with a hydraulic pore diameter to 2.29 μm and average pore size of 1.727 μm. The characterization of the raw effluent showed high levels of COD (1,125.4 mg.L-1), turbidity (1,300 UNT), and color (253.8 UC). The filtration study indicated good results of membrane efficiency, with removal of turbidity (99.3%), COD (95.7%), color (83.0%), phenolic compounds (82.1%), and solids (85.1 to 90%). The rice husk ash accomplished the function as pore-form agent and adsorbent of phenolic compounds and represented a promising alternative for incorporating the waste into the production cycle.

RESUMO A indústria de processamento de papel está entre as três maiores produtoras de águas residuais de significativa contaminação ambiental. Com o objetivo de minimizar os impactos nos corpos d’água e se adequar aos padrões exigidos pela legislação, são necessárias soluções avançadas de tratamento. Neste trabalho, uma membrana cerâmica de microfiltração foi desenvolvida, tendo como base 60% da composição correspondente ao resíduo de cinza de casca de arroz e 40% de Caulim, para ser aplicada como pré-tratamento do efluente real da indústria de papel. A membrana foi obtida por compactação uniaxial a 27 MPa em uma prensa elétrica, com posterior sinterização em mufla a 1.200°C por 1 hora. Os materiais foram caracterizados por análises químicas e físicas. A membrana apresentou porosidade aparente de 34,59%, densidade de 1,30 g/cm³, retração linear de diâmetro e espessura de 1,7 e 2,5%, respectivamente, perda ao fogo de 9,3% e boa estabilidade química em ácido e base. A permeabilidade hidráulica correspondeu a 11,3 × 10-3 m3/m2 s MPa-1, com diâmetro hidráulico de poros de 2,29 μm e tamanho médio de poros de 1,727 μm. A caracterização do efluente bruto revelou altos teores de demanda química de oxigênio (1.125,4 mg•L-1), turbidez (1.300 UNT) e cor (253,8 UC). O estudo de filtração indicou resultados satisfatórios de eficiência da membrana, com remoção de turbidez (99,3%), demanda química de oxigênio (95,7%), cor (83,0%), compostos fenólicos (82,1%) e sólidos (85,1 a 90%). O uso da cinza de casca de arroz desempenhou a função de agente formador de poros e adsorvente de compostos fenólicos, representando promissora alternativa para a incorporação do resíduo ao ciclo produtivo.