A global concern in the modern era is the widespread pollution of the environment and water bodies from plastic waste and heavy metals. This mounting threat to human and planetary health is exacerbated by the 19–23 million tonnes of plastic leaking every year into the world’s oceans, rivers, and lakes, according to the United Nations (UN) Environment Programme (UNEP).
Water is at the core of sustainable development and plays an indispensable role in human wellbeing and prosperity as well as ecological and environmental health. However, in recent decades overexploitation, pollution, growing populations, increasing consumption and climate change have led to severe water stress in locales across the world. This puts in jeopardy the achievement of the majority of the United Nations Sustainable Development Goals.
According to the World Wildlife Fund (WWF), 2.7 billion people face water shortages for at least one month each year. It is anticipated that almost half the world’s population will face severe water scarcity by 2030 if no urgent action is taken. The WWF estimates that over the past 120 years, two-thirds of all natural wetlands have been destroyed, and the population of freshwater animals has also declined by more than three-quarters since 1970, with one third of all freshwater species facing extinction.
Most of the planet’s water is the sea, with approximately only 3% of the world’s water being fresh water. Most of this water is locked up in ice or underground aquifers. When it comes to surface water, only about 0.3% of freshwater is found in lakes, rivers, and swamps, according to National Geographic.
This scarce resource is under severe pressure from agricultural, industrial and human-generated pollution such as nitrates, faecal matter, plastic and heavy metals. Plastic and heavy metal pollution have a profound impact on the environment, biodiversity and human well-being. Heavy metals such as copper, cadmium, zinc, aluminium, mercury, and lead are major metal pollutants in both drinking and wastewater. Lead stands out as one of the most toxic heavy metals to both plants and animals.
A gradual accumulation of lead in the human body over time leads to severe health issues, including damage to the liver, brain, kidneys, and reproductive system. Children are particularly vulnerable to the neurotoxic effects of lead, according to the World Health Organization (WHO), which states that lead exposure causes a significant burden of disease: it is estimated that lead exposure accounts for 0.9 million deaths per year (IHME, 2020) and 30% of the global burden of developmental intellectual disability of unknown origin (WHO, 2019). The WHO has identified lead as one of 10 chemicals of major public health concern needing action by member states.
Children are ingesting lead from different sources, including contaminated water, food and toys (paints). These heavy metals cause diseases like anaemia, nervous system disorders, hypertension, renal (kidney) damage, abdominal pain, constipation, and others, ultimately resulting in developmental disorders and increased mortality rates over a prolonged period. There are a few reasons why children are more vulnerable to heavy metals, including lead: (i) higher intake per body weight; they drink more water relative to their size, (ii) immature detox systems; liver and kidneys are still developing, (iii) developing brain; more sensitive to neurotoxins like lead and mercury, and lastly (iv) longer life ahead; increased risk of developing long-term chronic diseases [1–4].
Tackling the problem particularly of lead pollution in water bodies, through the use of biodegradable polymer composites filled with lead-adsorbing materials emerges as a viable solution to some of these problems.
It is in this context that the research undertaken by Prof Julia Puseletso Mofokeng, Associate Professor and researcher in the Department of Chemistry at the University of the Free State (UFS), seeks to improve water purification systems through the development of fully biodegradable polymer composites or nanocomposites adsorbents/membranes. The goal is to contribute to the reduction of water and environmental pollution from natural causes, petroleum-based plastics used in disposable products, and industrial waste.
Through engagement with industry, her research improves the environmental sustainability and water purification processes. This is important for water-scarce countries, especially in rural localities which often rely on raw river or groundwater.
Prof Mofokeng prepares and characterises fully biodegradable polymers, their blends and composites/nanocomposites, by incorporating carbonaceous materials, natural fibres and inorganic nanofillers, to enhance the thermal, thermomechanical, mechanical, and barrier properties of these materials. The research is aimed at providing sustainable alternatives to conventional petroleum-based plastics/polymers for short shelf-life/disposable applications. This approach targets applications in packaging, water purification, disposable medical devices, and automotive interiors. The current focus is water purification, where she and her research group use GO and its composites, synthesised from expandable graphite (EG), and transition metal phosphates, masked with completely biodegradable polymers like polylactic acid (PLA), Poly(3-Hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), and poly(Ɛ-caprolactone) (PCL) as adsorbents for the removal of heavy metal ions (lead, copper, chromium, mercury) in water. These biopolymers or biodegradable polymers are derived from renewable resources like vegetable oils and starches, aiming to replace petroleum-based plastics in disposable products applications. They can therefore be easily disposed of after use without harming the environment. A few of her published research articles under the topic are referenced at the end..
Several adsorbents have been explored to eliminate lead ions from water, including zeolites, activated carbon, and alumina, ordered mesoporous carbon, and silica gel. However, most of them are either costly to formulate or dispose of after use, thereby limiting their effectiveness. Recently, graphene oxide (GO) has emerged as a promising adsorbent for lead ions in water. Current research demonstrates GO’s high efficiency in removing lead ions. This effectiveness is attributed to the abundant oxygen-containing functional groups within its structure, enabling lead ion removal through both chemical and physical mechanisms.
In one of her recent studies, Preparation of poly(lactic acid) (PLA)/poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)/graphene oxide (GO) polymeric composites for the selective removal of lead ions (Pb(II)) in water, published in the journal Polymer Composites, the researchers intended to formulate GO-filled PLA/PHBV blends and assess their water intake, as well as Pb(II) ion adsorbing capabilities for different contact times and pH media. The findings of this work could set a path for developing effective and environmentally friendly materials to be used industrially, in removing lead ions from water by membrane filtration/batch adsorption processes and help alleviate lead poisoning. In this research, all the prepared samples showed the capability to adsorb lead ions from water, but the highest adsorption was observed at the lower GO content, and the optimal sample was the one with equal parts of the polymers, since leaching/degradation did not happen. Prof Mofokeng and her PhD student, Mr Lebohang Seromo, are working on featuring transition metal phosphates into GO which they expect to result in increased oxygen-containing groups on GO, thereby improving its metal ions adsorption capacity/efficiency further.
The research on biodegradable polymer composites/nanocomposites is envisioned as a transformative force in addressing the global water and plastic pollution crisis. It will also influence policymakers to enforce strict laws governing the production and retail industries to use biopolymers or biodegradable polymers in disposable packaging materials.
