This review highlights advancements made in anion exchange membrane (AEM) head groups, polymer structures and membrane synthesis methods. Limitations of current analytical techniques for characterizing AEMs are also discussed. AEM research is primarily driven by the need to develop suitable AEMs for the high-pH and high-temperature environments in anion exchange membrane fuel cells and anion exchange membrane water electrolysis applications. AEM head groups can be broadly classified as nitrogen based (e.g. quaternary ammonium), nitrogen free (e.g. phosphonium) and metal cations (e.g. ruthenium). Metal cation head groups show great promise for AEM due to their high stability and high valency. Through ''rational polymer architecture'', it is possible to synthesize AEMs with ion channels and improved chemical stability. Heterogeneous membranes using porous supports or inorganic nanoparticles show great promise due to the ability to tune membrane characteristics based on the ratio of polymer to porou2s support or nanoparticles. Future research should investigate consolidating advancements in AEM head groups with an optimized polymer structure in heterogeneous membranes to bring together the valuable characteristics gained from using head groups with improved chemical stability, with the benefits of a polymer structure with ion channels and improved membrane properties from using a porous support or nanoparticles. AbbreviationsAAEM Alkaline anion exchange membrane AEM Anion exchange membrane AEMFC Anion exchange membrane fuel cell AEMWE Anion exchange membrane water electrolysis CEM Cation exchange membrane DSC Differential scanning calorimetry IEC Ion exchange capacity (mmol/g) IEM Ion exchange membrane PEMFC Proton exchange membrane fuel cell

This paper provides a comprehensive statistical study on the topic of ion exchange membranes and may provide an avenue for future research work in this field.

Biotreatment of wastewaters containing toxic compounds can be jeopardized by surges in substrate concentration. Preventative measures include tight monitoring and control to either dilute high concentration transients, or to divert them to surge tanks for later release and treatment. Using phenol as a typical toxic substrate, we have imposed 4 h phenol surges of 3,000, 6,000 and 8,000 mg/l from a steady-state feed of 500 mg/l, demonstrating such reduced treatment efficiency. In contrast, with the addition to the bioreactor of a small amount (3-10 % w/v) of inert polymer beads (Hytrel 8206) possessing a high affinity for phenol (partition coefficient of 39), significant detoxification was achieved, resulting in a 100 % increase in treatment efficiency, and good performance at phenol surges of up to 16,000 mg/l. The addition (passive operation) of polymers to a biotreatment system eliminated the need for intervention during toxic transients while, at the same time, demonstrating that the polymers perform this function automatically and at all times (aggressive operation).

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