Ramp rate-controlled mineralogical evolution and multi-scale structure–property framework for arsenate removal in nanohematite-bearing clay ceramic water filters

Abstract

Sintering kinetics govern phase evolution and structure–property relationships in clay-based ceramics, yet the influence of heating rate on mineralogical evolution and filtration performance remains poorly understood. Here, ferruginous clay ceramic water filters were used to develop a multi-scale process–structure–property framework linking sintering ramp rate to mineralogical restructuring, hematite crystallographic evolution, transport behaviour, and arsenate removal. The raw clay contained high Fe₂O₃ ( 28.22 wt . % ) and an intrinsic nanohematite phase ( RHPA = 18.26 % , D = 12.43 nm ), providing an in-situ iron oxide phase relevant to arsenate adsorption. Ramp rate regulated hematite abundance and crystallographic characteristics, while multi-criteria optimisation integrating porosity, transport performance, densification, structural integrity, and hematite reactivity identified an optimum ramp rate of ⁻ ¹ 4 ° C min ⁻ ¹ . Under these conditions, arsenate concentrations were reduced from µ ⁻ ¹ 22.70 ± 1.50 to 9.91 ± 0.34 µg L ⁻ ¹ ( 56.3 % removal), achieving compliance with WHO guidelines. Zeta potential measurements revealed a transition from a strongly negative surface charge in the raw clay ( − 32.1 ± 1.4 mV ) to a near-neutral charge in the optimised filter ( + 1.3 ± 0.2 mV ), consistent with arsenate adsorption occurring predominantly through inner-sphere interactions on hematite-bearing surfaces. The optimised filter retained 92.9 ± 2.6 % of its flexural strength after prolonged aqueous exposure, indicating good structural stability. These findings establish sintering ramp rate as a key design parameter governing the evolution and performance of ferruginous ceramic filtration materials.