Batch and fixed-bed column studies of selenite removal from contaminated water by orange peel-based sorbent

Orange peel is a biomass derived from citrus processing with desirable properties for metal sorption.In recent years,orange peel has been used to remove various heavy metals and toxic oxyanions.Selenium(Se)is an essential trace element for mammals.However,when the concentration of selenium exceeds an umbral limit,it becomes toxic.In this study,orange peel was used to treat Se(IV)-contaminated water.A high sorption capacity of 32.5 mg/g was obtained at a temperature of 20℃and a pH of 2.0.Hydroxyl groups bound Se(IV)to the surface of the orange peel.The sorption process was spontaneous and endothermic.A chemical sorption mechanism was involved in the removal of Se(IV).The Thomas and modified dose-response models were used to simulate the experimental breakthrough curves.The bed depth service time model was used to calculate the critical bed depth(Z0),and the calculated Z0 value was 1.6 cm.This study reveals that orange peel is a useful sorbent for Se(IV),and can be used for the purification of Se(IV)-contaminated water.©2020 Hohai University.Production and hosting by Elsevier B.V.This is an open access article under the CC BY-NC-ND license(http://creativecommons.org/licenses/by-nc-nd/4.0/).

The synthesis and application of zeolitic material from fly ash by one-pot method at low temperature

A new route to prepare zeolitic material was introduced in this work. Compared with traditional methods, the new route showed lower energy consume. The effect of pre-treatment conditions on structure and crystalline phase was investigated, revealing that the mullite crystalline phase in fly ash could be converted to amorphous phase by alkali at low temperature. The removal performance of heavy metal ions on designed material was also investigated, and we found that the intermediate product showed higher adsorption capacity on Ni^(2+) than zeolite A.

Recovery and Upgrading of Phosphorus from Digested Sewage Sludge as MAP by Physical Separation Techniques

Physical separation apparatuses;a vibrating screen, a 4-inch hydrocyclone and a Multi-Gravity Separator (MGS) were used to recover phosphorus as MAP (magnesium ammonium phosphate, MgNH4PO4.6H2O) from anaerobic digested sludge of two sewage-treatment plants A and B. For plant A, the MAP grade increased from 0.08% to 88.9% with 90.4% recovery and for plant B, the grade increased from 0.11% to 73.8 with 93.2% recovery. The collected MAP products containing impurities such as organic materials and heavy metals were further upgraded through dry and wet magnetic separation tests at different magnetic flux densities. A dry magnetic separator was tested on both MAP products (MAP-A and MAP-B), while the wet magnetic separation process was exclusively experimented for the removal of impurities from MAP-B. Feed samples, as well as magnetic and nonmagnetic products were analyzed by absorption spectroscopy, XRD, ICP-AES, polarizing microscope observation, and SEM-EDX. The grade of MAP products could be improved by about 4% - 9% after magnetic separation (the most appropriate magnetic force being 15,000 Gauss). During both dry and wet magnetic separation processes, not only heavy metals have been removed, but also nonmagnetic constituents like Al, Ba, and Ca. This may be attributed to the attachment of fine magnetic particles on the nonmagnetic surfaces, rendering them magnetic properties.