Precipitation of organic arsenic compounds and their degradation products during struvite formation

Abstract

Roxarsone (ROX) and arsanilic acid (ASA) have been extensively used as organoarsenic animal feed additives. Organic arsenic compounds and their degradation products, arsenate (As(V)) and arsenite (As(III)), exist in the effluent from anaerobic reactors treating animal manure contaminated by ROX or ASA with ammonium (NH4(+)-N) and phosphate (PO4(3-)-P) together. Therefore, arsenic species in the effluent might be involved in the struvite formation process. In this study, the involvement of organic arsenic compounds and their degradation products As(V) and As(III) in the struvite crystallization was investigated. The results demonstrated that arsenic compounds did not substantially affect the PO4(3-)-P recovery, but confirmed the precipitation of arsenic during struvite formation. The precipitation of arsenic compounds in struvite was considerably affected by a solution pH from 9.0 to 11.0. With an increase in pH, the content of ASA and ROX in the precipitation decreased, but the contents of As(III) and As(V) increased. In addition, the arsenic content of As(V) in the struvite was higher than that of As(III), ASA and ROX. The results indicated that the struvite could be contaminated when the solution contains arsenic species, but that could be minimized by controlling the solution pH and maintaining anaerobic conditions during struvite formation.

Sulfide and arsenic compounds removal from liquid digestate by ferric coagulation and toxicity evaluation

“…The removal mechanism of sulfide and arsenic by coagulation is summarized in Table 2. A remarkable peak around 43.82 eV could also be observed with the help of X-ray spectra, which represents As(III) 3d orbit. The results of high-resolution XPS scan revealed that As(III) was the main form of arsenic in the liquid digestate and could be efficiently removed during ferric coagulation, which was consistent with the results of previous research on the form of arsenic in the anaerobic conditions (Lin, Yuan, Wang, Hu, & Yu, 2016).…”

Effective removal of arsenate from wastewater using aluminium enriched ferric oxide-hydroxide recovered from authentic acid mine drainage

“…To abate and manage the challenges of arsenic in the environment several studies have explored methods for the removal of arsenic from water. These techniques include ion exchange [15], reverse osmosis [16], coagulation [17], precipitation [18], electro-sorption [19], and adsorption [20]. However, most of these technologies suffer from disadvantages including the generation of toxic sludge and high costs of operation and maintenance.…”