Sustainable conversion of textile industry cotton waste into P-dopped biochar for removal of dyes from textile effluent and valorisation of spent biochar into soil conditioner towards circular economy.

Effective immobilization of industrial waste into biochar development could be one of the most promising technologies for solid waste management to achieve circular economy. In this study, post-industrial cotton textile waste (PICTW), a cellulose rich industrial waste, was subjected to slow pyrolysis to develop a surface engineered biochar through phosphoric acid impregnation. Biochar produced at 500 °C designated as PICTWB500 showed a maximum methylene blue number (240 mg g-1) with remarkable specific surface area of 1498 m2 g-1. FESEM, FTIR, XRD and Raman spectra analysis were performed to investigate the surface texture and functionalities developed in the biochar. Adsorption efficiency of the biochar was assessed using drimarene red, blue, violet, and black dyes as model dye pollutants in batch mode at different biochar dose, pH and contact time. The maximum monolayer adsorption capacity was obtained in the range 285-325 mg g-1 for different dyes, determined from Langmuir adsorption model. The kinetic behaviour was more favourable with the pseudo second-order model. The recycling ability of PICTWB500 was proven to be effective up to 6th cycle without compromising its adsorption efficiency significantly. This study demonstrated an excellent adsorption capability of the biochar in dye laden real textile effluent and recycling of spent biochar as a precursor of bio compost. Hence, this study established a dual win strategy for waste utilization in textile industry using a closed loop approach with substantial techno-economic feasibility that may have potential applications.

Performance assessment of the indigenous ceramic UF membrane in bioreactor process for highly polluted tannery wastewater treatment.

The present study evaluates the performance of an indigenously developed ceramic ultrafiltration (UF) membrane in a lab-scale membrane bioreactor (MBR) process to treat real tannery effluent with varying organic loading (1500-6000 mg/L). UF membrane was prepared by the coating of bentonite clay on tubular clay-alumina macroporous support. The membrane surface was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, BET adsorption-desorption, contact angle measurement, and atomic force microscopy. In the side-stream MBR process, sewage sludge from a local sewage treatment plant was used as an activated sludge source with a constant sludge retention time of 30 days. Membrane filtration was performed in cross-flow mode using a single-channel membrane module. Artificial neural network (ANN) modeling tool was used to analyze the influence of various independent input variables, namely, the hydraulic retention time (4-10 h), mixed liquor suspended solid (MLSS) concentration (2-8 g/L), and influent COD concentration (1500-6000 mg/L) on COD removal (%) with feed-forward backpropagation method. Membrane study was done at a transmembrane pressure of 4.3 bar and feed flow rate of 7.5 L/min to observe the flux declination and fouling of the UF membrane with time. Average COD and BOD concentrations obtained in the treated effluent were 147.56 and 31 mg/L, respectively, and chromium concentration was < 0.1 mg/L; thus, treated effluent quality was found to be suitable for industrial recycling purposes apart from the safe environmental discharge. An in-depth study was undertaken to understand the removal mechanism in the MBR process, nature and extent of membrane fouling, changes in the morphology of the UF membrane, surface wettability, and surface topology by detailed surface characterization of the membrane pre- and post-filtration.

Ceramic membrane-based ultrafiltration combined with adsorption by waste derived biochar for textile effluent treatment and management of spent biochar.

PURPOSE: Effluents produced in the textile industries are important sources of water pollution due to the presence of toxic dyes, auxiliary chemicals, organic substances etc. Recycling of such industrial wastewater is one major aspect of sustainable water management; hence present study is focused on an eco-friendly process development for reclamation of higher loading textile wastewater. METHOD: Industrial effluent samples with varying loading were collected from textile processing units located in and around Kolkata city. Vegetable waste collected from local market was utilized to prepare an efficient biochar for elimination of the recalcitrant dyes. Prior to adsorption, ceramic ultrafiltration (UF) process was used for reduction of the organic loading and other suspended and dissolved components. RESULTS: A remarkably high BET surface area of 1216 m2g-1 and enhanced pore volume of 1.139 cm3g-1 was observed for biochar. The maximum adsorption capacity obtained from the Langmuir isotherm was about 300 mg.g-1. The combined process facilitated >99% removal of dyes and 77-80% removal of chemical oxygen demand (COD) from the various samples of effluent. The treated effluent was found suitable to discharge or reuse in other purposes. About 95% of dye recovery was achieved during biochar regeneration with acetone solution. The dye loaded spent biochar was composted with dry leaves and garden soil as bulking agent. Prepared compost could achieve the recommended parameters with high nutritional value after 45 days. CONCLUSIONS: The overall study showed potential of the proposed process towards treatment of toxic dye loaded textile effluent in an environment friendly and sustainable approach.