Heidi Richards

University of the Witwatersrand | wits · School of Chemistry

Acid mine drainage (AMD) remains a global threat with no exception to South African water bodies and the environment. It promotes environmental challenges with emerging concerns on water security and drinking water pollution. This study evaluated membrane distillation crystallization (MDC) towards resource recovery from AMD. To ensure high process...

In recent years, trace organic compounds (TOrCs) and emerging contaminants (ECs) have been detected in different water sources including surface water and wastewater. Such compounds include but not limited to pharmaceuticals, hormones, personal care products, per- and polyfluoroalkyl substances (PFASs), disinfection by-products, flame retardants, a...

Membrane distillation (MD) has emerged as a novel technology capable of recovering fresh water from brackish, saline, and wastewater. However, its industrial application is limited to various challenges including membrane properties. In this work, the polyvinylidene fluoride (PVDF) membranes were modified to improve their performance towards desali...

In this study, hydrophobic functionalized carbon nanotubes (fCNTs) and silica nanoparticles (fSiO2NPs) were incorporated into polyvinylidene fluoride (PVDF) flat-sheet membranes to improve their performance in membrane distillation (MD). The performance of the as-synthesized membranes was evaluated against commercial reference polytetrafluoroethyle...

Biofouling in membrane distillation (MD) severely impacts the process performance and significantly reduces membrane lifespan. Herein, polyvinylidene fluoride (PVDF) was modified with silver nanoparticles (AgNPs) embedded on cellulose nanocrystals (CNCs), mainly to endow antibacterial properties to the PVDF membrane. The synthesis of CNC-capped AgN...

Fungi characterized by metabolic properties are believed to efficiently synthesize several metal nanoparticles (NPs), including copper (Cu) NPs. Several studies have reported biomineralization processes for the synthesis of CuNPs. During the synthesis process, proteins play a critical role in the transformation and biologically induced biomineraliz...

Oil spillage and industrial discharge of oily wastewater threaten the health of the human beings and the environmental life. To perform oil cleaning from the water bodies, several physicochemical methods have been employed. However, these methods experience various challenges hindering their absolute usage. To curb these problems, smart materials a...

Membrane distillation crystallization (MDC) is an emerging technology envisaged to manage challenges affecting the desalination industry. This technology can sustainably treat concentrated solutions of produced water and industrially discharged saline wastewater. Simultaneous recovery of clean water and minerals is achieved through the integration...

Membrane distillation (MD) is envisaged as a cost-effective water desalination technology. When operated by low-grade energy, MD surpasses the cost challenges faced by other water desalination technologies. Although MD operates under conditions that minimize the survival of biofilm causing microorganisms, their development and succession is being i...

In this study, zeolitic imidazolate frameworks (ZIF) were employed as effective porous supports for laccase enzyme attachment and further explored synergistic adsorption and biocatalytic degradation of carbamazepine (CBZ) in aqueous solutions. Characterization results from FTIR and NMR analysis confirmed successful incorporation of the laccase enzy...

Acid mine drainage (AMD) has been a source of environmental contamination in many parts of the world. This is because many countries depend on mining as a source of revenue. However, waste tailing dumps often leach out toxic waste with high levels of metal ions and flow downstream to dams and rivers. The current remediation methods (passive and act...

This work aimed at optimizing the QuEChERS method with PSA and then comparing it with Moringa Oleifera seed protein as a clean-up sorbent for the extraction of endocrine-disrupting chemicals. The response surface methodology approach was used in the optimization. A design of experiment (DoE) was used to investigate the effect of the sample mass (0....

The present study highlights the synthesis of a polypyrrole (Ppy) composite based on Macadamia nutshells (AMN) and binary metal oxides (Mn-Cu oxide) for the selective removal of Cr(VI) from aqueous solution. Ppy/AMN-Mn-Cu oxide nanocomposite was synthesized via in-situ oxidative polymerization of pyrrole monomer using FeCl3 as an oxidant in the pre...

The measurement of trace metals in polluted mine waters remain a concern due to its adverse effects on human health. In this manuscript, the evaluation of a Macadamia-derived activated carbon (MAC), modified with KMnO4 and HNO3, is reported on. The modification resulted in the increased content of oxygen-containing functional groups on the MAC adso...

Obtainable from Water Research Commission Private Bag X03 Gezina PRETORIA 0031 orders@wrc.org.za or download from www.wrc.org.za DISCLAIMER This report has been reviewed by the Water Research Commission (WRC) and approved for publication. Approval does not signify that the contents necessarily reflect the views and policies of the WRC, nor does men...

Fish inhabiting freshwater environments are susceptible to the ingestion of microplastics (MPs). Knowledge regarding MPs in freshwater fish in South Africa is very limited. In this study, the uptake of MPs by common carp (Cyprinus carpio) in the Vaal River in South Africa was assessed. MPs were detected in all of the twenty-six fish examined, 682 p...

Silver nanoparticles (AgNPs) have attracted substantial attention in several research fields owing to their unique physicochemical properties, which make them suitable for industrial, biotechnological, and commercial applications (e.g., coatings, catalysts, biological markers/probes, etc.). Similarly, the potential use of AgNPs in agriculture has b...

Due to the toxicity of trace metals and the propensity of fishes to bioaccumulate metals in their tissues, we investigated the concentrations of arsenic (As), cadmium (Cd), copper (Cu), iron (Fe), lead (Pb), mercury (Hg), and zinc (Zn) in the muscles of tilapia (Oreochromis mossambicus) and catfish (Chrysichthys nigrodidatatus) collected from open...

This review reports on the increasing interest in technical designs, calibration, and application of PIM-based devices in sample pre-treatment and passive sampling in environmental water monitoring from 2010 to 2021. With regards to passive sampling, devices are calibrated in a laboratory setup using either a dip-in or flow-through approach before...

This work demonstrates development and evaluation of a two-way technique based on the combination of membrane assisted solvent extraction and a molecularly imprinted polymer (MASE-MIP) for selective and efficient extraction of five selected pharmaceuticals belonging to five different therapeutic classes. The pharmaceuticals were extracted from surf...

The occurrence of pharmaceuticals in the environmental waters is a global concern. There is little research conducted on the monitoring of pharmaceuticals in the marine environment. In this article, the occurrence of pharmaceuticals and their metabolites in the coastal waters as well as associated risks related to their uptake by marine organisms a...

The presence of trace metals in polluted mine water remains a concern due to its adverse effects on human health. This paper evaluates a PVC-D2EHPA based PIM containing silver nanoparticles as a tool to extract and measure trace metals in polluted water. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), contact angle a...

Neutralization that results in the precipitation of high‐density sludge (HDS) remains the preferred method for treating acid mine drainage (AMD). The HDS is usually discharged onto landfills, with little further exploitation and thus poses an environmental challenge. This study proposes aims at using various neutralizing agents (e.g., NaOH, CaCO3,...

The shortcomings of conventional sampling methods as grab sampling has led to the development of alternative approaches especially those based on passive samplers. The challenge of passive sampler’s despite being cheap to use and being integrative in nature is that there are limited commercial suppliers especially for those on water related applica...

Acid mine drainage (AMD) poses significant challenges to fresh water supplies in mining regions globally. Not only is water made too acidic for consumption, the acidic conditions also lead to the mobilization of toxic elements including uranium. Nanomaterials have been shown to be effective for the treatment of such contaminated water. In this stud...

Mercury contamination of freshwater supplies poses a significant challenge to fresh water supplies, particularly in regions with historical or current gold mining. Nanomaterials are increasingly explored for the remediation of mercury-contaminated water due to their unique properties. Here, we report on the application of reduced graphene oxide (rG...

This study investigated whether differential pulse anodic stripping voltammetry (DPASV) with a solid gold electrode could be used for arsenic speciation of mine-influenced water. The DPASV parameters were optimized using a 100-µg L −1 As(III) standard solution. The procedure for chemical reduction of As(V) to As(III) using thiosulfate prior to DPAS...

A smart sorbent consisting of benzo[k]fluoranthene-imprinted and indeno[1 2 3-cd]pyrene-imprinted polymers mixed at 1:1 (w/w) was successfully screened from several cavity-tuning experiments and used in the isolation of polycyclic aromatic hydrocarbons from spiked solution. The polymer mixture showed high cross selectivity and affinity towards all...