Chromium Adsorption on Banana Rachis Adsorbent from Tannery Wastewater: Optimization, Isotherm, Kinetics and Desorption Studies

This study investigates the banana rachis adsorbent for adsorption characterization, removal, and recovery of the chromium ion from the chrome tanning wastewater. The batch analysis was conducted to find out an adsorbent dose, contact time, relative pH of the aqueous solution, and initial and final chromium value in the filtrate. The equipped adsorbent was studied by the Fourier transform infrared spectroscopy (FT-IR) analysis to reveal the associated functional groups during adsorption. Batch adsorption examination reveals the optimum conditions of 3 g adsorbent input for 75 mL wastewater at 15 min contact time. The adsorption mechanism showed chromium removal 99.64% with the obtained reduction of biochemical oxygen demand (BOD), chemical oxygen demand (COD), and chloride (Cl-) 96.65%, 93.18%, and 59.62%, respectively. The adopted method followed the pseudo-second-order kinetics and Freundlich isotherm for physical adsorption. Primary desorption studies exhibit a scope for the reuse of chromium from the adsorbed adsorbent. Moreover, in comparison with other studies, the study discloses that banana rachis might be utilized as a feasible adsorbent to be adopted in industrial wastewater treatment, especially chrome tanning wastewater in the tannery

Microrecycling solution for conversion of waste plastics into high quality products using available machinery

Plastic revolutionised the world, but meantime generates a substantial amount of waste plastics. However, plastics are generally non-biodegradable and hence remain in the environment for a very long time. Most plastics are not discarded properly, these wastes either end up in the landfills or left in the environment which can end up in water systems including oceans. Alternatively, plastics are burned to remove from premises or to recover energy. Today it is well established that if waste plastics are not deal properly, they can pose a great risk to both the people and the environment and at the same time a lot of valuable materials will be lost. However, only a small percentage of waste plastic is currently recycled due to the limitations of recycling and reprocessing technology, which requires massive infrastructure and normally is not economically feasible and environmentally sustainable. To overcome these challenges, several easy-to-operate and less cost incentive processes have been evaluated throughout this PhD project. This project first began by investigating the effect of reprocessing on polymer, which is important to develop efficient and effective recycling processes. At the next step a simple process that required fewer steps has been developed to utilise waste hard plastics as feedstock to produce new plastic products whilst retaining the original properties and colour of input waste plastics. Then, two novel processes have been demonstrated for another two types of problematic waste plastic (fishing net and flexible plastic packaging). In the final part of this research, three-dimensional (3D) printing, an advanced method of manufacturing, has been employed to transform waste plastics from toys into products. All produced plastics from the proposed methods showed good mechanical performances as virgin material. Life cycle assessment indicated that the processes could reduce greenhouse gas emission, fossil fuel depletion and ecotoxicity. Considering the conclusions of this project, different methods demonstrated in this thesis can manage and transform a wide range of waste plastics (from hard to soft) into high-quality plastics. They are not limited to the case studied waste plastics rather they have the potential to deal with other similar kinds of waste plastic. Overall, this research will create value for waste plastics, and in turn, speed up their collection and recycling

Study on the Direct Transformation of Milk Bottle and Wood into Wood–Plastic Composite through Injection Molding

Plastic has transformed the world; however, it generates a huge amount of waste plastics. It is well evident that, if urgent action is not undertaken on plastic pollution, it will pose threats to not only the environment, but also human life. Just simply discarding waste plastics will result in wasting a lot of valuable materials that could be recycled. Recently, the use of waste plastics has been considered for producing wood plastic composites (WPCs), which are superior to normal wood. Waste plastics are pelletized using an extruder and are then subjected to injection molding. In this study, investigations were carried out to determine the possibility of producing WPCs without the palletization of waste plastic to turn WPC production into a shorter, simple, and easy-to-achieve process. Here, a waste milk bottle, a familiar single-use plastic, was picked as a case study. Waste plastic granules and wood particles were mixed and directly injection molded to produce valuable WPCs. The water absorption of WPCs with 20% wood is 0.35%, and this increased to 0.37% when wood content was increased to 40%. The tensile strength at yield, elongation at break, and impact strength of WPCs with 20% wood content are 19.54 MPa, 5.21%, and 33.92 KJ/m2, respectively, whereas it was 17.23 MPa, 4.05%, and 26.61 KJ/m2 for the WPCs with 40% wood content. This process can be a potential solution for two problematic wastes at the same time

Thermal Transformation of Secondary Resources of Carbon-Rich Wastes into Valuable Industrial Applications

Carbon-based materials have become an indispensable component in a myriad of domestic and industrial applications. Most of the carbon-based end-of-life products discussed in this review end up in landfills. Where recycling is available, it usually involves the production of lower-value products. The allotropic nature of carbon has been analysed to identify novel materials that could be obtained from used products, which also transform into a secondary carbon resource. Thermal transformation of carbon-rich wastes is a promising and viable pathway for adding value to waste that would otherwise go to landfills. The valorisation routes of four different carbon-rich wastes by thermal transformation are reviewed in the study—automotive shredder residue (ASR), textile wastes, leather wastes, and spent coffee grounds (SCGs). Textile wastes were thermally transformed into carbon fibres and activated carbon, while ASRs were used as a reductant to produce silicon carbide (SiC) from waste glass. The leather wastes and spent coffee grounds (SCGs) were employed as reductants in the reduction of hematite. This paper examines the possible routes of thermally transforming carbon-rich wastes into different industrial processes and applications. The transformation products were characterised using several techniques to assess their suitability for their respective applications. The strategy of valorising the wastes by thermal transformation has successfully prevented those wastes from ending up in landfills