Removal of orthophosphates in water by modified carbonate material of biological origin

Abstract

The excessive release of phosphorus (P) by discharge of domestic and industrial effluents is directly associated with the eutrophication of water bodies. Therefore, an efficient removal of P from effluents is required. The method most commonly used for P removal from wastewater is chemical precipitation. However, this technique is relatively expensive and demands a proper disposal for the sludge. Therefore, the development of new materials with low cost but high P removal efficiency has been investigated. The introduction of exotic species in aquatic environments is considered a serious environmental problem in different parts of the world. Considering that, many of these species have high concentrations of carbonates in their exoskeleton composition, which is potentially useful in water treatment, particularly for P removal the use of such material as adsorbent has been tested. The present study aimed to investigate the capacity of the exoskeleton of exotic species in powder form to remove orthophosphates from water comparing the raw material (RCS), with physically modified (CSA) and chemically modified (CSC) material. To study the orthophosphates removal efficiency, a factorial design with central composite rotational design (CCRD) was applied. In order to optimize the P removal, the influence of the independent variables adsorbent/adsorbate ratio, pH and temperature was investigated with the kinetic control associate at each configuration obtained by CCRD. The P removal capacity of RCS varied from 125.0 mgP kg-1 to 1002.5 mgP kg^-1; the removal capacity of CSA varied from 237.5 mgP kg^-1 to 1540.0 mgP kg^-1. The removal capacity of CSC varied from 5212.5 mgP kg^-1 to 12672.5 mgP kg^-1. Based on the preliminary results, the exoskeleton powder showed to be a potentially sustainable alternative as adsorbent material (mostly the chemically modified form CSC) useful in several applications, such as the treatment of urban and industrial wastewaters to prevent eutrophication of water bodies and population control of exotic species due to the commercial exploitation.