<p>Heavy metal contamination of water is a major environmental and public health problem due to the toxicity, persistence, and bioaccumulation of these contaminants. Carbon nanotube (CNT) based nanomaterials are being studied extensively because of their large specific surface area, tunable surface chemistry, high mechanical strength and fast adsorption rates. Among all the available technologies, this has proven to be an effective and sustainable treatment technology. In this review, recent development of CNT-based adsorbents for the removal of heavy metal ions from water has been critically discussed, highlighting the correlation between surface functionalization, adsorption mechanisms, operating conditions, regeneration and applicability. The effect of pH, temperature, contact time, adsorbent dosage and competing ions on adsorption performance is described. The corresponding mechanisms and the characterization techniques have been explored. The strategies for enhancing adsorption efficiency and selectivity have been emphasized. In addition, the challenges that must be overcome to achieve large-scale commercialization are reviewed, with synthesis cost, regeneration, environmental safety, real wastewater performance and sustainability being discussed. Lastly, future research directions focusing on scalable synthesis, computational modelling, life-cycle assessment and pilot-scale validation are given. This review summarizes the adsorption performance and implementation issues of CNT-based technologies for sustainable water and wastewater treatment and ultimately offers a comprehensive framework for the development of commercially viable technologies.</p>