Evaluation of the efficiency of three different mineral adsorbents in the removal of pollutants in samples from a tropical spring in Northeastern Brazil

Abstract

Human water sources are increasingly threatened around the world due to various sources of pollution such as agriculture and industry. The objective of this study was to evaluate three new adsorbents as pollutant remedies for subsequent application in the Joanes River located in the State of Bahia in Brazil. The specific pollutants were nitrogen, phosphorus (P), aluminum (Al), iron (Fe), cyanobacteria, and saxitoxins. Initially, studies (pH 7 and 22°C) were performed with samples contaminated in the laboratory with phosphorus (P), nitrate ( NO3-), and ammonia (NH3), to select the most efficient adsorbent and to determine the equilibrium time. Pumice bituminous coal was found to have the best efficiencies (≥70%) at 360 min (equilibration time). The experimental data did not fit the Langmuir and Freundlich model. The bituminous coal with pumice stone was then applied to water samples from a designated capture point of the Joanes springs, a river system that is responsible for supplying the city of Salvador and the metropolitan region, located on the northern coast of Bahia. The removal efficiency analyses were performed on a DR6000 UV/VIS SPECTROPHOTOMETER, using the methodology defined in the Standard Methods 2017, after which this adsorbent was subjected to scanning electron microscopy. As a result, removal efficiencies (≥98%) were obtained for all contaminants (nitrogen, phosphorus (P), aluminum (Al), iron (Fe), cyanobacteria, and saxitoxins) as well as a highly heterogeneous layer pointed by SEM images, further demonstrating the adsorbent potential as a efficient alternative in environmental control after additional studies. Practitioner points Pumice bituminous coal has proven to be an excellent adsorbent for a wide range of pollutants such as phosphorus, nitrogen, ammonia, toxins, cyanobacteria, and metals. The adsorbent promoted a high reduction in phosphorus concentrations (3.40 mg/L to 0.01 mg/L), about 98% and 81% for cyanobacteria (12,850 Cel/ml to 2,560 Cel/ml). The adsorbent promoted a high reduction in concentrations of 98% saxitoxins (4.32 µg/L to 0.2 µg/L).

A Carboxyl-Functionalized Covalent Organic Polymer for the Efficient Adsorption of Saxitoxin

“…For trace or ultra-trace analysis of organic contaminants from water samples, pretreatment and pre-concentration are often required prior to the quantification [56], and extraction techniques such as solid-phase extraction (SPE) [25], magnetic solid-phase extraction (MSPE) [11,18], and solid-phase microextraction (SPME) [4] have been developed for the concentration of STX. On the other hand, for saxitoxin removal, the most common method is based on adsorption using granular activated carbon (GAC) [34], although other adsorbent materials have also been reported, such as polymeric resins [36], mineral residues [3,12], oyster shell powder [26], and algal polysaccharide gels [29]. However, complicated implementation procedures, low specificity and adsorption capacity, and poor reusability of the reported adsorbents prompt the development of novel highly efficient and recyclable materials for STX adsorption [21,25,36].…”

Editorial: Surmounting challenges in natural and engineered water systems

“…Meanwhile, I highly recommend other twelve equally excellent articles in the same issue. In the drinking water treatment aspect, three mineral adsorbents were studied for alleviation of multiple contaminants in source water in Northeastern Brazil (Guimarães Neto & Aguiar, 2020), while effects of coagulant types and doses, as well as water properties, were evaluated for coagulation removal of different engineered nanoparticles in water (Ramirez Arenas, Ramseier Gentile, Zimmermann, & Stoll, 2020). In the municipal wastewater treatment field, simultaneous nitrite‐shunt and biological phosphorus removal were demonstrated at low dissolved oxygen in a full‐scale high‐rate water reclamation facility (St. Petersburg, Florida) (Jimenez et al., 2020); and the process optimization and kinetic behaviors of the struvite precipitation for phosphorus removal and recovery were studied (Wang, Tian, Wang, & Yan, 2020).…”