A Novel Nanoporous Adsorbent for Pesticides Obtained from Biogenic Calcium Carbonate Derived from Waste Crab Shells.

A novel nanoporous adsorbent was obtained through the thermal treatment and chemical wash of the wasted crab shells (BC1) and characterized by various techniques. The structure of BC1 at the end of the treatments comprised a mixture of calcite and amorphous CaCO ₃ , as evidenced by X-ray diffraction and Fourier transform infrared absorption. The BET surface area, BET pore volume, and pore diameter were 250.33 m ² g ^-1 , 0.4 cm ³ g ^-1 , and <70 nm, respectively. The point of zero charge of BC1 was determined to be around pH 9. The prepared adsorbent was tested for its adsorption efficacy towards the neonicotinoid pesticide acetamiprid. The influence of pH (2-10), temperature (20-45 °C), adsorbent dose (0.2-1.2 g L ^-1 ), contact time (5-60 min), and initial pesticide concentration (10-60 mg L ^-1 ) on the adsorption process of acetamiprid on BC1 was studied. The adsorption capacity of BC1 was 17.8 mg g ^-1 under optimum conditions (i.e., 20 mg L ^-1 initial acetamiprid concentration, pH 8, 1 g L ^-1 adsorbent dose, 25 °C, and 15 min contact time). The equilibrium data obtained from the adsorption experiment fitted well with the Langmuir isotherm model. We developed an effective nanoporous adsorbent for the recycling of crab shells which can be applied on site with minimal laboratory infrastructure according to local needs.