Desenvolvimento de compósitos de cimento com diferentes dosagens de lodo de ETA e zeólitas: caracterização e modelagem cinética para remoção de fósforo em solução e água residuária

Abstract

Phosphorus (P), an essential element for life and of great importance in the industrial and/or agro-industrial production chain, in surface waters contribute to different levels of trophy. To minimize intercurrents such as these, the implementation of adsorption strategies has stood out as a complementary method to conventional effluent treatment processes. In this context, the objective of this study was to develop cementitious composites with different dosages of Water Treatment Plant (WTP) sludge and zeolites, and to evaluate their performance through characterization and kinetic modeling, for the removal of phosphorus in solution and in swine wastewater (SRW). The P concentrations were 25, 50, 75 and 100 mg L-1, submitted to the treatments from T1 to T6, for the percentages of cement, sludge and zeolites applied in the following order: T1 (100%, 0%, 0%), T2 (50%, 50%, 0%), T3 (50%, 10%, 40%), T4 (50%, 25%, 25%), T5 (50%, 40%, 10%) and T6 (50%, 0%, 50%). The adsorptive effect of P was evaluated for phosphate concentration, final pH value, ionic strength, as well as kinetic and isothermal aspects. The physical, chemical and morphological characterization of the composites was carried out in terms of water absorption, porosity and compressive strength, Fourier transform (FTIR) and scanning electron microscopy (SEM). All treatments led to considerable removal of P, in which the tested concentration of 25 mg L-1 of P and the maximum concentration of 100 mg L-1 of P, the minimum and maximum efficiencies were 79.3% (1.19 mg g-1) to 96.6% (1.45 mg g-1) and 26.3% (1.58 mg g-1) to 41.1% (2.47 mg g-1), respectively. For ARS with 34 mg L-1 of P, an efficiency of 46.2% was achieved using the T4 treatment (50%, 25%, 25%), showing superiority to the amount adsorbed at equilibrium with a value of 3.81 mg g-1, compared to the treatments in P solution, for the same concentration range. The physical (compressive strength), chemical (FTIR) and morphological (SEM) characterization tests showed that cementitious composites consisting of 50% cement, produced with 25% WTP sludge and 25% zeolites on a laboratory scale, demonstrated better adequacy to the potential for P recovery in solution and in ARS to treat concentrations of the chemical species up to 100 mg L-1. The production and application of these materials is promising, as it strengthens the reuse and environmentally correct disposal of waste, such as WTP sludge, as well as recognizes the structural performance of cement binder, as a primordial material to unite different aggregates in mass, in which together they collaborate for the adsorptive process of P.