Resource recovery from soiled sanitary napkin waste-a state-of-the-art review.

With ever-improving social and medical awareness about menstrual hygiene in India, the demand for sanitary napkins has increased significantly. The utilization of high-quality and environment-friendly raw materials to produce these pads is further supporting the growth of the market. However, with improving demand and usage, the need for proper disposal techniques becomes more relevant, since all of these pads get contaminated with human blood which makes them a biohazard and can cause significant damage to human health and the environment. One sanitary pad takes around 800 years to degrade naturally and the plastic and super absorbent polymers (SAPs) in sanitary pads are non-biodegradable and can take multiple decades to degrade. Waste management technologies such as pyrolysis, gasification, and resource recovery can be adopted to manage tons of sanitary waste. Currently, sanitary waste treatment mainly focuses on landfilling, incineration, and composting, where biohazard wastes are mixed with tons of solid waste. Disposable sanitary pads have a high carbon footprint of about 5.3 kg CO2 equivalent every year. Innovative solutions for sanitary pad disposal are discussed in the manuscript which includes repurposing of derived waste cellulose and plastic fraction into value-added products. Future aspects of disinfection strategies and value addition to waste cellulose recovered from napkins were systematically discussed to promote a circular economy.

Electrochemical-based approaches for the treatment of pharmaceuticals and personal care products in wastewater.

In recent times, emerging contaminants (ECs) like pharmaceuticals and personal care products (PPCPs) in water and wastewater have become a major concern in the environment. Electrochemical treatment technologies proved to be more efficient to degrade or remove PPCPs present in the wastewater. Electrochemical treatment technologies have been the subject of intense research for the past few years. Attention has been given to electro-oxidation and electro-coagulation by industries and researchers, indicating their potential to remediate PPCPs and mineralization of organic and inorganic contaminants present in wastewater. However, difficulties arise in the successful operation of scaled-up systems. Hence, researchers have identified the need to integrate electrochemical technology with other treatment technologies, particularly advanced oxidation processes (AOPs). Integration of technologies addresses the limitation of indiviual technologies. The major drawbacks like formation of undesired or toxic intermediates, s, energy expenses, and process efficacy influenced by the type of wastewater etc., can be reduced in the combined processes. The review discusses the integration of electrochemical technology with various AOPs, like photo-Fenton, ozonation, UV/H2O2, O3/UV/H2O2, etc., as an efficient way to generate powerful radicals and augment the degradation of organic and inorganic pollutants. The processes are targeted for PPCPs such as ibuprofen, paracetamol, polyparaben and carbamezapine. The discussion concerns itself with the various advantages/disadvantages, reaction mechanisms, factors involved, and cost estimation of the individual and integrated technologies. The synergistic effect of the integrated technology is discussed in detail and remarks concerning the prospects subject to the investigation are also stated.

Conversion of plastic waste into fuel oil using zeolite catalysts in a bench-scale pyrolysis reactor.

Catalytic pyrolysis of mixed plastic waste to fuel oil experiment was tested with ZSM-5 zeolite (commercial and synthesized) catalysts along with other catalysts. The ZSM-5 zeolite catalyst was effectively produced using a hydrothermal technique via metakaolin as an alumina source. The catalytic pyrolysis of different types of plastic (single and multilayer) wastes in the presence of various catalysts was tested with a bench-scale pyrolysis setup with 2 kg per batch capacity. Polyolefin based plastics (low-density polyethylene, high-density polyethylene, and polypropylene), multilayer plastics such as biaxial oriented polypropylene (BOPP), metalized biaxial oriented polypropylene layers (MET BOPP), polyethylene terephthalate (PET), metalized polyethylene terephthalate (MET/PET), polyethylene terephthalate combined polyethylene (PET/PE), and mixed plastic waste collected from the corporation sorting center were pyrolyzed in a batch pyrolysis system with 1 kg feed to determine the oil, gas and char distributions. The performances of commercial ZSM-5 and lab synthesized ZSM-5 catalysts were compared for the pyrolysis of non-recyclable plastic wastes. Other commercial catalysts including mordenite and gamma alumina were also tested for pyrolysis experiments. The gross calorific value of oil obtained from different combinations of multilayer packaging waste varied between 10 789-7156 kcal kg-1. BOPP-based plastic waste gave higher oil yield and calorific value than PET-based plastic waste. Sulfur content present in the oil from different plastic wastes was measured below the detection limit. The synthesized ZSM-5 zeolite catalyst produced a maximum oil output of 70% and corresponding gas and char of 16% and 14% for LDPE plastic. The strong acidic properties and microporous crystalline structure of the synthesized ZSM-5 catalyst enables increased cracking and isomerization, leading to an increased breakup of larger molecules to smaller molecules forming more oil yield in the pyrolysis experiments. Residual char analysis showed the maximum percentage of carbon with heavy metal concentrations (mg kg-1) in the range of viz., chromium (15.36-97.48), aluminium (1.03-2.54), cobalt (1.0-5.85), copper (115.37-213.59), lead (89.12-217.3), and nickel (21.05-175.41), respectively.

Treatment of petroleum oil spill sludge using the combined ultrasound and Fenton oxidation process.

In this paper, advanced oxidation process (AOP) combining ultrasound (US) and Fenton's process was proposed for the treatment of total petroleum hydrocarbons present in oil spill sludge. The effect of several parameters like pH, ultrasonic power, weight ratio of hydrogen peroxide to iron [H2O2/Fe2+], Fenton reagent dosage, addition of salts and contact time were analyzed for the reduction of Petroleum Hydrocarbons (PHCs) in terms of hydrocarbon fractions (nC7-C10, nC11-C20). Chemical characterization of oil spill sludge was analysed by gas chromatography- mass spectrum (GC-MS) Elemental analyser, Fourier Transform Infra Red (FT-IR) Analyser and particle size analyser. Experiments were conducted for identifying the wide range of hydrocarbons fractions (nC7-C10, nC11-C20 and nC21-C30). Results shown that maximum solubilisation and PHC removal rate of up to 84.25% could be achieved at a pH of 3.0, sludge/water ratio of 1:100, ultrasonic power of 100 W with 40-50% ultrasonic amplitude, a H2O2/Fe2+ weight ratio of 10:1, and an ultrasonic treatment time of 10 min. The lower and medium fractions (nC7-C10, nC11-C20) were amenable to degradation due to ultrasound treatment compared to the heavier carbon fraction (nC21-C30). The study concludes that the combined sono-Fenton (SF) process significantly enhanced the degradation of oil spill sludge as compared to ultrasound treatment and Fenton oxidation alone. The enhanced solubilisation achieved by US alone is highly beneficial when we couple this with biodegradation which will be greatly facilitated by the enhanced solubility.

Microwave (MW) remediation of hydrocarbon contaminated soil using spent graphite - An approach for waste as a resource.

In this study, we have explored the possibility of using an industrial waste for remediation of heavy fuel oil contaminated soil. Microwave (MW) heating in the presence of spent graphite (SG) from an auto forging industry has been used for the remediation. The physico-chemical characterization of SG and contaminated soil were done. Microwave remediation experiments were conducted in a lab scale unit and the effect of different parameters like microwave power, susceptor loading and treatment time were studied and optimized. The contaminated and decontaminated soils were analysed using GC-MS for total petroleum hydrocarbons (TPH), Total Organic Carbon and CHNS analyzers. Batch experiments of soil remediation showed that the TPH removal efficiencies (%) of 41.25, 87.77 and 91.18 at 300, 450 and 600 W respectively at SG concentration of 2.5 (wt. %) for a reaction time of 60 min. The addition of SG as susceptor enhanced the desorption of long chain hydrocarbons (C12-C29) present in the soil. Desorption of hydrocarbons from the soil fits well with first order kinetic model. This study successfully demonstrated the reuse of spent graphite (a lubricant waste) recovered from metal forging operations for remediating the fuel oil contaminated soil.