Removal of Arsenate and Chromate by Lanthanum-modified Granular Ceramic Material: The Critical Role of Coating Temperature

The development of economical, low-maintenance, environmentally friendly and effective water filtration techniques can have far-reaching public health, social and economic benefits. In this research, a cost-effective La-modified granular ceramic material made of red art clay and recycled paper fiber was developed for the removal of two major anionic contaminants, As(V) (arsenate) and Cr(VI) (chromate). La modification temperature significantly impacted the resulting composition and properties of the adsorbents, and thus played a crucial role in the adsorbent performance. The La-modified ceramic materials were extensively characterized through scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) surface area measurement, thermal gravimetric analysis (TGA), zeta potential measurements, and Fourier-transform infrared spectroscopy (FTIR) analysis. The characterization results suggested that surface coating by LaONO(3)-related compounds was critical for As(V) and Cr(VI) adsorption. At the modification temperature of 385 °C, the adsorption of As(V) and Cr(VI) reached maximum, which were 23 mg/g and 13 mg/g, respectively, under circumneutral conditions that are relevant to various aquatic systems. The adsorption kinetics and isotherm, the influence of pH, ionic strength and coexisting anions on As(V) and Cr(VI) adsorption were investigated to further understand both As(V) and Cr(VI) adsorption behavior. Findings from this research showed that La-modified ceramic material made of recycled paper waste represents a cost-effective adsorbent for anionic contaminant removal under environmentally relevant conditions.