Powdered silk: A promising biopolymer for the treatment of dye contaminated water.

Discharge of textile dye effluents into water bodies is creating stress to aquatic life and contaminating water resources. In this study, a new biopolymer adsorbent silk fibroin (SF) was prepared from Bombyx mori silk fibroin (SF) and used for removal of Solochrome Black-T (SB-T) from water. This innovative adsorbent exhibits an exceptional adsorption capacity of 20.08 mg/g, achieving a removal efficiency of approximately 98.6 % within 60 min. Notably, the powdered SF adsorbent demonstrates rapid kinetics, surpassing the performance of previously reported similar adsorbents in adsorption capacity and reaction speed. The molecular weight and particle diameter of the material were observed to be > 1.243 kDa and 3 µm, respectively. The experimental investigations were performed on different parameters, viz., adsorbent dosage, contact time, repeatability, and desorption-adsorption study. The experimental data well fit for the Langmuir model (R2 = 0.937, qmax = 20.08 mg/g) and the pseudo-second-order kinetics (R2 = 0.921 and qe = 1.496 mg/g). Compared to the adsorbents reported in the literature, the newly prepared SF showed high adsorption capacity and faster kinetics to address real-life situations. The novelty of this work extends beyond its remarkable adsorption capabilities. The SF adsorbent offers a cost-effective, sustainable solution and regenerable adsorption material with minimal negative environmental impacts. This regenerability, with its versatility and broad applicability, positions powdered SF fibroin as a transformative technology in water treatment and environmental protection.

Silk fibroin: a promising bio-material for the treatment of heavy metal-contaminated water, adsorption isotherms, kinetics, and mechanism.

Silk is the strongest natural biopolymer produced by silk worms possessing superior adsorbent properties and thus extensively used in various applications. The present study involved the preparation of powder form of a silk fibroin materials and their application in adsorption of heavy metals, particularly, iron from aqueous solution. The morphological and structural characteristic properties of this promising materials were examined by using different analytical techniques. Batch experiments were conducted within feasible parametric ranges to understand the effect of dose, time, concentration, pH, and reusability. Silk fibroin was effective for iron adsorption over a wide range of pH 6 to 10. The adsorption removal efficiency of 98% was attained for removal of iron from contaminated water at moderate dose of 0.25 g and contact time of 60 min, which is unprecedented by considering the environment benign nature of the material. The data was examined in different isotherm models wherein it fitted best in Langmuir adsorption model. Similarly, Langmuir isotherm model, with R2 value of 0.984 and KL 0.412 and maximum adsorption capacity as 12.82 mg g-1, suggests monolayer adsorption. Kinetic study with better R2 value of 0.941 represented the pseudo-second order kinetics governed by the chemisorption reaction. To understand the practical applicability of silk fibroin, the repeatability study up to 5 cycles were performed. The findings are very encouraging which confirmed the usage of silk fibroin as adsorbent for multiple cycles with marginal decrease in adsorption efficiency. Eventually, the material was tested for iron removal in real contaminated water which revealed its potential and selectivity for removal of iron in different matrix.