Development of natural dye photosensitizers for dye-sensitized solar cells: a review.

Dye-sensitized solar cell (DSSC) is a photovoltaic device that can be produced from natural source pigments or natural dyes. The selection of natural dyes for DSSC application is currently under research. The utilization of natural dye materials that are easy to obtain, cost-effective, and non-toxic can reduce waste during DSSC fabrication. Natural dyes can be extracted from plants through extraction and chromatography methods. The suitability and viability of utilizing natural dyes as photosensitizers in DSSCs can be predicted using appropriate software simulation by varying related parameters to produce high power conversion efficiency. In this context, the purpose of the review is to highlight the evolution of performance improvement in the development of DSSCs with consideration of natural dye extraction and software simulation. This review also focuses on the results of extracting natural dyes from herbal ingredients, which are still very limited in information, and several parts of herbal plants that can be used as natural dye sources in the future of solid-state DSSCs have been identified. Based on the results of this review, the highest efficiency was obtained for the DSSC that used chlorophyll pigments as natural dyes using Peltophorum pterocarpum leaves with 6.07%, followed by anthocyanin pigments as natural dyes using raspberries (black) fruits with 1.5%, flavonoid pigments as natural dyes using Curcuma longa herbs with 0.64%, and flavonoid pigments as natural dyes using Indigofera tinctoria flowers with 0.46%.

Recycling phosphorus and calcium from aquaculture waste as a precursor for hydroxyapatite (HAp) production: a review.

Water contaminated with phosphorus needs to be managed efficiently to ensure that clean water sources will be preserved. Aquaculture plays an essential role in supplying food and generating high revenue. However, the quantity of phosphorus released from aquaculture effluents is among the major concerns for the environment. Phosphorus is a non-renewable, spatially concentrated material essential for global food production. Phosphorus is also known as a primary source of eutrophication. Hence, phosphorus recovery and separation from different wastewater streams are mandatory. This paper reviews the source of phosphorus in the environment, focusing on aquaculture wastewater as a precursor for hydroxyapatite formation evaluates the research progress on maximizing phosphorus removal from aquaculture wastewater effluents and converting it into a conversion. Shrimp shell waste appears to be an essential resource for manufacturing high-value chemicals, given current trends in wealth creation from waste. Shrimp shell waste is the richest source of calcium carbonate and has been used to produce hydroxyapatite after proper treatment is reviewed. There have been significant attempts to create safe and long-term solutions for the disposal of shrimp shell debris. Through the discussion, the optimum condition of the method, the source of phosphorus, and the calcium are the factors that influence the formation of hydroxyapatite as a pioneer in zero-waste management for sustainability and profitable approach. This review will provide comprehensive documentation on resource utilization and product development from aquaculture wastewater and waste to achieve a zero-waste approach.

Scenario modelling of proxy system in the context of Malaysian food flow management.

The research on food flow network is unpredictable as the approaches employed are more targeted at specific study points, often excluding spatial and temporal changes. The research questions must still address why and how food flow moves in the entire supply chain system. This study aims to investigate the movement of food flow using national statistics, comprising of four main subsystems: agriculture, nutrition, waste, wastewater management, and the environment by using the Material Flow Analysis (MFA) approach. Comprehensive research using primary and secondary data including literature reviews have successfully bridged the knowledge gap on food supply chain management in Malaysia. This article provides new contributions through the considerations of food safety and the opportunity to understand flow issues that are connected to hotspots, closed flow, and economic circulars. Additionally, this study acts as a simple guide for policymakers to manage the imbalances of food supply in certain areas. From the perspective of food waste management, several important strategies were successfully formulated to combat the leakage of food waste flow and financial burden while highlighting the need for local social actors' involvement to fulfil Malaysia's agenda of Sustainable Development Goals.

Environmental Performance of Small-Scale Seawater Reverse Osmosis Plant for Rural Area Water Supply.

Seawater desalination is an alternative technology to provide safe drinking water and to solve water issues in an area having low water quality and limited drinking water supply. Currently, reverse osmosis (RO) is commonly used in the desalination technology and experiencing significant growth. The aim of this study was to analyze the environmental impacts of the seawater reverse osmosis (SWRO) plant installed in Kampung Pantai Senok, Kelantan, as this plant was the first installed in Malaysia. The software SimaPro 8.5 together with the ReCiPe 2016 database were used as tools to evaluate the life cycle assessment (LCA) of the SWRO plant. The results showed that the impact of global warming (3.90 kg CO2 eq/year) was the highest, followed by terrestrial ecotoxicity (1.62 kg 1,4-DCB/year) and fossil resource scarcity (1.29 kg oil eq/year). The impact of global warming was caused by the natural gas used to generate the electricity, mainly during the RO process. Reducing the environmental impact can be effectively achieved by decreasing the electricity usage for the seawater desalination process. As a suggestion, electricity generation can be overcome by using a high-flux membrane with other suitable renewable energy for the plant such as solar and wind energy.

Effect of Conway Medium and f/2 Medium on the growth of six genera of South China Sea marine microalgae.

A study was performed to determine the effect of Conway and f/2 media on the growth of microalgae genera. Genera of Chlorella sp., Dunaliella sp., Isochrysis sp., Chaetoceros sp., Pavlova sp. and Tetraselmis sp. were isolated from the South China Sea. During the cultivation period, the density of cells were determined using Syringe Liquid Sampler Particle Measuring System (SLS-PMS) that also generated the population distribution curve based on the size of the cells. The population of the microalgae genera is thought to consist of mother and daughter generations since these microalgae genera reproduce by releasing small non-motile reproductive cells (autospores). It was found that the reproduction of Tetraselmis sp., Dunaliella sp. and Pavlova sp. could be sustained longer in f/2 Medium. Higher cell density was achieved by genus Dunaliella, Chlorella and Isochrysis in Conway Medium. Different genera of microalgae had a preference for different types of cultivation media.

Study on the removal of pesticide in agricultural run off by granular activated carbon.

In this batch study, the adsorption of malathion by using granular activated carbon with different parameters due to the particle size, dosage of carbons, as well as the initial concentration of malathion was investigated. Batch tests were carried out to determine the potential and the effectiveness of granular activated carbon (GAC) in removal of pesticide in agricultural run off. The granular activated carbon; coconut shell and palm shells were used and analyzed as the adsorbent material. The Langmuir and Freundlich adsorption isotherms models were applied to describe the characteristics of adsorption behavior. Equilibrium data fitted well with the Langmuir model and Freundlich model with maximum adsorption capacity of 909.1mg/g. The results indicate that the GAC could be used to effectively adsorb pesticide (malathion) from agricultural runoff.

The formation and characterisation of an asymmetric nanofiltration membrane for ammonia-nitrogen removal: effect of shear rate.

The focus of this research is to study the potential of nanofiltration membrane technology in removing ammonia-nitrogen from the aquaculture system. One of the major fabrication parameters that directly affect the separation performance is shear rate or casting rate during membrane fabrication. In this study, asymmetric polyethersulfone (PES) nanofiltration membranes were prepared at five different shear rates within the range of 67-400 s(-1). Membrane productivity and separation performance were assessed via pure water, salt and ammonia-nitrogen permeation experiments, and their structural properties were determined by employing the combination of the irreversible thermodynamic (IT) model, solution diffusion model, steric hindrance pore (SHP) model and Teorell-Meyers (TMS) model. The study reveals that the alteration of shear rate enormously affects the membrane morphology and structural parameters, hence subsequently significantly influencing the membrane performance. It was found that, membrane produced at the shear rate 200 s(-1) or equivalent to 10s of casting speed during membrane fabrications managed to remove about 68% of ammonia-nitrogen, in which its separation performance is the most favourable by means of highest flux and rejection ability towards unwanted solutes. Besides, from the research findings, nano-membrane technology is a potential candidate for the treatment of aquaculture wastewater.