Assessment of the efficacy of Aspergillus sp. EL-2 in textile waste water treatment

Sequential electron beam and bioflocculation for treatment of textile nanodyes

Nanodyes are a new class of hazardous materials that are used in textile coloring. Their small size, color, stability and high dispersion characteristics pose a huge threat if they are released in open water systems. The aim of the present study is to test electron beam irradiation, bioflocculation and their sequential use for nanodye removal. The nanodye was obtained from a factory and was characterized using UV-visible spectroscopy, Fourier transform infra-red (FTIR) spectroscopy, dynamic light scattering, zeta potential and energy dispersive X-ray (EDX). The obtained results show that applying 7.5 kGy electron beam irradiation results in complete color removal in 10 min for 50 and 100 ppm nanodye, while at 200 and 400 ppm concentrations, the decolorization reaches 90% but leaving a residual brownish color. Adding 5 mg mL^-1 of Serratia marcescens N2 biosurfactant resulted in agglomeration of 80% dye removal for 400 ppm nanodye after 24 h. On the other hand, the use of sequential electron beam and bioflocculation led to an initial removal of 80% in 1 h. The residual dyes were tested for toxicity on normal dermal HFB4 cells. The toxicity result was 1.19% after electron beam treatment, while those for sequential treatment and bioflocculation were 6.28 and 6.9%, respectively. It can be concluded that electron beam technology provides fast and highly efficient nanodye removal, while biosurfactants offer a low-cost, eco-friendly approach with a chance for dye retrieval.

Toxic effects of Red-S3B dye on soil microbial activities, wheat yield, and their alleviation by pressmud application

This study examined the effect of Red-S3B textile dye on soil microbial activities, uptake of the dye by wheat plants and growth on the dye-contaminated soil. Moreover, pressmud (PM) application was investigated for its alleviative effect on wheat yield and dye uptake by plants. Preliminarily, soil was spiked with a wide concentration range (0, 100, 250, 500, 750 and 1000 mg kg^-1 soil) of Red-S3B dye and wheat was grown for 42-days. The dye did not suppress the activities of soil enzymes and growth of wheat seedlings at 100 mg kg^-1; however, beyond this level the dye had a linear negative effect on these attributes. With 1000 mg dye kg^-1 soil, wheat seedling biomass, viable microbial count, soil respiration, dehydrogenase, phosphatase, and urease activities decreased by 84%, 33%, 45%, 69%, 24%, and 11%, respectively as compared to uncontaminated soil. Moreover, phosphorus and potassium content in wheat shoot decreased, while the nitrogen content increased in Red-S3B contaminated soil. In the subsequent pot experiment, PM application (12.5 g kg^-1 soil) was assessed to alleviate the adverse effect of moderately toxic level of Red-S3B dye (500 mg kg^-1 soil) on wheat growth and yield. Root and straw biomass, and grain yield of wheat decreased by 13, 19 and 12%, respectively in Red-S3B contaminated soil as compared to uncontaminated soil. However, PM application to dye-contaminated soil retrieved the dye-induced reduction in root and straw biomass and grain yield to become statistically (p ≤ 0.05) at par with control plants. The color of Red-S3B was clearly visible in spikes depicting that plants absorbed Red-S3B but probably could not metabolize it. Amending the dye-contaminated soil with PM decreased Red-S3B content in awns from 78 to 37 mg kg^-1. Hence, it is concluded that Red-S3B textile dye is highly toxic to soil microbes and wheat plants at levels exceeding 100 mg kg^-1 soil. Soil application of PM alleviates the adverse effect of Red-S3B dye on wheat growth through reducing its uptake by plants.

Comparative study for adsorption of methylene blue dye on biochar derived from orange peel and banana biomass in aqueous solutions

Biochar pyrolyzed at 800 °C from banana (B_b) and orange peels (OP_b) was applied for sorption of methylene blue (MB) dye in a batch system. OP_b showed better affinity for MB dye than B_b with rapid increase in sorption capacity and percent removal for both biochars attaining equilibrium at 30 min. Chemisorption was suggested as the rate limiting step based on the best fitting of the pseudo-second-order reaction kinetics to the batch adsorption data. Linear increase in sorption capacity was seen as the initial MB dye concentration increased from 50 to 300 mg g^-1 with a 40 % decrease in removal efficiency. An increase of 90 mg g^-1 in sorption capacity for both biochars with a 15 and 30 % increase in removal efficiency for OP_b and B_b, respectively, was observed after increasing the solution pH from 2 to 6 or 8. An increase in sorption capacity of about 150 mg g^-1 was seen by increasing the biochar dose from 0.1 to 0.5 g. Langmuir isotherm model represented the adsorption data well as reflected by the high values of R² (0.99) when using both biochar, while least representation of adsorption data was seen in H-J isotherm as estimated from very low R² (0.6-0.66) for both types of biochar. An endothermic nature of MB dye sorption was suggested based on the linear increase in sorption capacity with an increase in solution temperature from 30 to 60 °C. This was further confirmed by the observed positive changes in standard entropy and standard enthalpy while negative values of Gibbs-free energies proposed the non-spontaneous natures of MB dye sorption on to both biochars. The effective sorption of MB dye demonstrated the potential of plant-based biochar as economically viable adsorbents for MB dye.