Colored wastewater poses a challenge to the conventional wastewater treatment techniques. Solid−liquid phase adsorption has been found to be effective for the removal of dyes from effluent. In this paper, the ability of bentonite as an adsorbent for the removal of a commercial dye, Basic Red 2 (BR2), from an aqueous solution has been investigated under various experimental conditions. The adsorption kinetics was shown to be pseudo-second-order. It was found that bentonite had high adsorption capacity for BR2 due to cation exchange. The adsorption equilibrium data can be fitted well by the Langmuir adsorption isotherm model. The effect of the experimental parameters, such as temperature, salt, and pH was investigated through a number of batch adsorption experiments. It was found that the removal of dye increased with the increase in solution pH. However, the change of temperature (15−45 °C) and the addition of sodium chloride were found to have little effect on the adsorption process. The results show that electrostatic interactions are not dominant in the interaction between BR2 and bentonite. It was found that the adsorption was a rapid process with 80−90% of the dye removed within the first 2−3 min. Bentonite as an adsorbent is promising for color removal from wastewater.

In this proof-of-concept study, an agricultural biocide (imidacloprid) was effectively loaded into the mesoporous silica nanoparticles (MSNs) with different pore sizes, morphologies and mesoporous structures for termite control. This resulted in nanoparticles with a large surface area, tunable pore diameter and small particle size, which are ideal carriers for adsorption and controlled release of imidacloprid. The effect of pore size, surface area and mesoporous structure on uptake and release of imidacloprid was systematically studied. It was found that the adsorption amount and release profile of imidacloprid were dependent on the type of mesoporous structure and surface area of particles. Specifically, MCM-48 type mesoporous silica nanoparticles with a three dimensional (3D) open network structure and high surface area displayed the highest adsorption capacity compared to other types of silica nanoparticles. Release of imidacloprid from these nanoparticles was found to be controlled over 48 hours. Finally, in vivo laboratory testing on termite control proved the efficacy of these nanoparticles as delivery carriers for biopesticides. We believe that the present study will contribute to the design of more effective controlled and targeted delivery for other biomolecules.

Highly ordered large-pore periodic mesoporous organosilica (PMO) with a rodlike morphology was successfully synthesized at low acid concentrations and in the presence of inorganic salt using triblock copolymer P123 as a template. The inorganic salt can not only promote the formation of highly ordered mesoporous structure but also control the morphology of PMO materials. The adsorption of bovine heart cytochrome c (cyt c) on PMO was studied at different ionic strengths and pHs by comparing with the adsorption on pure silica materials with similar morphology and pore structure. The results show that the adsorbed amount reaches the maximum around the isoelectric point of cyt c and the PMO materials do not have higher adsorbed capacity than SBA-15 silica. The specific adsorption amounts of cyt c on PMO or pure silica decrease as ionic strengths increase at all pH conditions. Our results directly support the conclusion that the electrostatic interaction between cyt c and PMO/pure silica surface is more dominant than hydrophobic forces in the bioadsorption of cyt c.