Nanostructured Gel-Phase Materials for Arsenic Removal from Water

Arsenic is present naturally in groundwater in many countries around the world; it affects over 140 million people in the world. Consumption of arsenic contaminated water has resulted in arsenic been named by the World Health Organisation (WHO) as one of the top 10 chemicals of public health concern, due to the toxicity of arsenic contaminated drinking water. Current commercial arsenic adsorbents such as activated carbon have low adsorption capacities. In this work, self-assembled cationic C16-DAPMA micelles based on palmitic acid and 3,3′-diamino-N-methyldipropylamine were investigated for interactions with arsenite (As III) and arsenate (As V). The properties of a gelator based on dibenzylidene sorbitol functionalized with hydrazide groups (DBS-CONHNH2) was investigated as a support for the micelles. The embedding of C16-DAPMA micelles into DBS-CONHNH2 hydrogels was investigated to determine whether it was suitable for use as an arsenic removal system. It was found that the C16-DAPMA micelles could bind arsenate through electrostatic interactions, due to the fact that arsenate exists as an anion in water. It was found that at 3.49 mM of arsenate, aggregation between arsenate and C16-DAPMA micelles occurred. It was found that C16-DAPMA micelles could be embedded into DBS-CONHNH2 hydrogels. The presence of C16-DAPMA micelles within DBS-CONHNH2 resulted in stiffer hydrogels, as C16-DAPMA micelles limited the entanglement of the self-spanning network and reduced its flexibility. It was found that C16-DAPMA micelles embedded within the DBS-CONHNH2 hydrogels (with agarose for added stability) were able to reduce the concentration of arsenate from 298 ppb to an estimated value of between 80 to 100 ppb. This work demonstrated that C16-DAPMA micelles embedded within DBS-CONHNH2 hydrogels have potential to be used as an alternative water filtration system due to cheap nature of the materials compared to commercial adsorbents. However, further work is required to prevent leaching of the micelles from the hydrogel network.