Sorptive removal of arsenate using termite mound

• High (∼99%) removal of As(V) by TM was achieved in a wide pH range 3–9.
• Film diffusion was not the only rate-limiting step in the adsorption of As(V) on TM.
• TM had high affinity for As(V) with 13.32 kJ/mol mean energy of sorption.
• Dissolution of TM was insignificant at pH ∼7 under the equilibrium experimental conditions.
• The As(V) loaded TM was regenerated using 0.2 M NaOH solution without significant loss of metals.

Long-term consumption of arsenic results in severe and permanent health damages. The aim of the study was to investigate arsenate (As(V)) sorption capacity of termite mound (TM), containing mainly silicon, aluminum, iron and titanium oxides, under batch adsorption setup. The pattern of As(V) removal with varying contact time, solution pH, adsorbent dose, As(V) concentration and competing anions was investigated. Dissolution of the adsorbent was insignificant under the equilibrium conditions. Equilibrium was achieved within 40 min of agitation time. Kinetic data of As(V) adsorption followed well the pseudo-second order equation (R2 > 0.99). High As(V) removal efficiency (∼ 99%) was observed over a pH range ∼ 3–∼ 10, which is of great importance in the practical application. The Freundlich and Dubinin–Radushkevich isotherms well described (R2 > 0.99, χ2 ∼ 0.05) the equilibrium As(V) adsorption, giving a coefficient of adsorption 1.48 mg1−1/nL1/n/g and a saturation capacity 13.50 mg/g respectively. The obtained value of mean sorption energy (EDR = 13.32 kJ/mol) suggested the chemisorption mechanism of As(V) adsorption on TM. The removal of As(V) was significantly decreased in the presence of phosphate ions. The As(V) loaded adsorbent was successfully regenerated using NaOH solution with insignificant loss of metals. Therefore, the results of the study demonstrated that TM could be considered as a promising adsorbent for the treatment of As(V) in drinking water.