Abstract
Copper (Cu2+), cadmium (Cd2+) and lead ions (Pb2+) are toxic to human beings and other organisms. In this study, a silica gel material modified with nitrilotriacetic acid (NTA-silica gel) was sensibly designed and prepared via a simple amidation procedure for the removal of Cu2+, Cd2+ and Pb2+ from water. The NTA-silica gels showed rapid removal performances for the three metal ions (Pb2+ (<2 min), Cu2+ and Cd2+ (<20 min)) with relatively high adsorption capacities (63.5, 53.14 and 76.22 mg g−1 for Cu2+, Cd2+ and Pb2+, respectively). At the same concentration of 20 mg L−1, the removal efficiencies of the three metals by the adsorbent ranged from 96% to 99%. The Freundlich and Langmuir models were utilized to fit the adsorption isotherms. The adsorption kinetics for the three metal ions was pseudo-second-order kinetics. The removal performance of the NTA-silica gels increased in a wide pH range (2–9) and maintained in the presence of competitive metal ions (Na+, Mg2+, Ca2+ and Al3+) with different concentrations. In addition, the NTA-silica gels were easily regenerated (washed with 1% HNO3) and reused for 5 cycles with high adsorption capacity. This study indicates that the NTA-silica gel is a reusable adsorbent for the rapid, convenient, and efficient removal of Cu2+, Cd2+, and Pb2+ from contaminated aquatic environments.
Highlights
Heavy metal ion pollution in wastewater is a signi cant hazard to human existence worldwide due to the non-biodegradability and high toxicity of metal ions to life
Due to the rapid globalization, the smelt industry, metal plating, electrolysis, mining operations, pigment and other industries discharge vast industrial sewage containing heavy metal ions,[1,2,3] and the concentrations of these metal ions are frequently higher than the national effluent emission standards for wastewater, especially drinking water
We developed a new heavy metal ion adsorbent, nitrilotriacetic acid (NTA)-silica gel, which was synthesized using aminated silica gel and the chelating agent NTA based on a cost-effective and easyoperation amidation reaction
Summary
Heavy metal ion pollution in wastewater is a signi cant hazard to human existence worldwide due to the non-biodegradability and high toxicity of metal ions to life. There are various types of metal ions inside effluents including Cu2+, Cd2+, and Pb2+, which accumulate inside living organisms, endangering the public health. The Abundant successful experimental technologies have been used to remove heavy metal ions from effluents, including chemical co-precipitation,[4] ion exchange,[5,6] reverse osmosis,[7] ultra ltration,[8] membrane ltration,[9] coagulation,[10] adsorption[11,12] and others.[13] Among them, the adsorption technology is known as a high-efficiency method due to its effectiveness, simplicity, low cost,[14,15,16,17,18] and regenerable adsorption capacity.[11,19] At concentrations lower than 100 mg LÀ1, the removal of metal ions better accomplished by adsorption.[20] Due to the advancement of adsorption technology, the development of new adsorbents has increased in recent years. To date, most of the adsorbents have poor adsorption capacities, ineffectiveness for low metal ion concentrations, slow kinetics and high costs.[21,22,23,24]
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