Performance of cationic hemicelluloses arising from peanut shell residue from agroindustry in application as primary coagulant in physical-chemical treatment of dairy wastewater

Abstract

Cationic hemicelluloses (CH) are increasingly studied as an alternative to the use of inorganic coagulants. However, the CH has been used as coagulation aids. In the present study shows its potential to be used directly as a coagulant in a physical chemical treatment of synthetic dairy wastewater (SDW). Hemicelluloses were cationized by etherification reaction in alkaline medium with ETA. FTIR indicated cationization by increase of the methyl group band (1475 cm−1), supported by theoretical analysis. CH elemental analysis showed 1.92% (±0.09) of nitrogen and degree of substitution (DS) of 0.32 (±0.01). Turbidity, apparent color, TSS, COD and BOD5.20 was performed in a jartest with coagulation pH (5–11) and dosages range (100–900 ppm). Coagulation diagrams were determined for spatial interpolation by Kringing regression model. The optimal point selected occurred at the dosage of 400 ppm (coagulation pH 9.00 and 7.38), promoting removals for CH/TSG, respectively, of: 94.79%/98.67% (turbidity); 56.72%/65.21% (apparent color); 79.76%/97,22% (TSS); 47.83%/62.50% (COD) and 73.93%/62.39% (BOD5.20). The flakes morphology was analyzed by the image capture non-intrusive method. Fractal dimension (Df) of the flakes stabilized after 10 min at values of 1.319 (±0.020) and 1.871 (±0.001), with range diameters of 0.023–0.254 mm and 0.032–5.718 mm, for CH and TSG, respectively. Consequently, CH are a promising alternative for application as primary coagulants, provided removal of turbidity, apparent color and organic matter, not altering the pH and not promoting addition of color in the SDW.