Nickel removal by the two-step synthesis of ceramsite from sediments and water hyacinth

Abstract

Dredged sediment (DS) and water hyacinth (WH) generated from dredging projects have the potential to pose environmental risks. A novel two-step method (cement solidification → low-temperature sintering) was developed to transform from DS and WH into outstanding ceramsite product. The performance of the ceramsite was analyzed using X-ray diffraction, fourier transform infrared spectroscopy, and scanning electron microscopy. Adsorption performance, kinetics, isotherms and corresponding remove mechanism to Ni2+ of ceramsite were also discussed. Results show that the main phase of optimized ceramsite (SCBF-20 %) included quartz, calcium carbonate, calcium dealuminate and monocalcium aluminate. The addition of WH improved the development of pores and cracks of ceramsite, which is favorable to Ni2+ adsorption. The adsorption kinetics and isotherm of SCBF-20 % could be expressed by pseudo-second order kinetics and Langmuir model. This indicated that SCBF-20 % was dominated by chemisorption, with a maximum adsorption capacity of 373 mg/g (in powder form). The removal mechanism of SCBF-20 % mainly included ion exchange of Ni with Ca, coordination reaction of Ni with oxygen atoms, and precipitation of hydroxide. Overall, SCBF-20 % demonstrated excellent dynamic removal efficiency for Ni2+ from actual wastewater.