Preparation of a New Iron-Carbon-Loaded Constructed Wetland Substrate and Enhanced Phosphorus Removal Performance

Abstract

Iron-carbon substrates have attracted extensive attention in water treatment due to their excellent processing ability. The traditional iron-carbon substrate suffers from poor removal effects, separation of the cathode and anode, hardening, secondary pollution, etc. In this study, a new type of iron-carbon-loaded substrate (NICLS) was developed to solve the problems of traditional micro-electrolytic substrates. Through experimental research, a preparation method for the NICLS with Fe and C as the core, zeolite as the skeleton, and water-based polyurethane as the binder was proposed. The performance of the NICLS in phosphorus-containing wastewater was analyzed. The results are as follows: The optimal synthesis conditions of the NICLS are 1 g hydroxycellulose, wood activated carbon as the cathode, an activated carbon particle size of 200-60 mesh, and an Fe/C ratio of 1:1. Acidic conditions can promote the degradation of phosphorus by the NICLS. Through the characterization of the NICLS (scanning electron microscope (SEM), X-ray diffractometer (XRD), and energy-dispersive spectrometer (EDS), etc.), it is concluded that the mechanism of the NICLS phosphorus removal is a chemical reaction produced by micro-electrolysis. Using the NICLS to treat phosphorus-containing wastewater has the advantages of high efficiency and durability. Therefore, it can be considered that the NICLS is a promising material to remove phosphorus.

Assessment of the Different Type of Materials Used for Removing Phosphorus from Wastewater

“…The specific procedure was as follows: 0.1 g of each adsorbent material was weighed into a 50 mL Erlenmeyer flask, 15 mL of a set concentration of phosphorus solution was added, and the pH of the solution was adjusted to 7.5 with 0.1 mol/L hydrochloric acid or 0.1 mol/L sodium hydroxide solution. The solution was shaken in a constant temperature shaker at 180 r/min and 25 °C for 24 h. A syringe was used to take out 10 mL of the supernatant from the Erlenmeyer flask and filter it with a 0.45 µm filter membrane; the phosphorus concentration in the filtrate was determined by ammonium molybdate spectrophotometry (950 Lambda UV-Vis-NIR Perkin Elmer, Waltham, MA, USA), and the removal capacity of phosphorus and phosphorus removal efficiency of each adsorbent was calculated according to Equations (3) and (4) [ 83 , 89 ]. A single-factor analysis method was used and blank and two parallel experiments were carried out.…”

“…For each adsorbent material the following procedure was used: 150 mL of a 400 mg/L phosphate solution was mixed with 0.1 g of adsorbent (adsorbent to solution ratio = 1:25) size in a series of 200 Erlenmeyer flasks. The pH of solution was 7.5 (adjusted with 0.1 mol/L hydrochloric acid or 0.1 mol/L sodium hydroxide solution) [ 83 , 89 ]. The flasks were kept at room temperature (25 °C) and 180 rpm, and samples were collected at different time intervals; phosphorus concentration was determined by ammonium molybdate spectrophotometry, and the corresponding removal capacity was calculated [ 83 ].…”

“…The pH of solution was 7.5 (adjusted with 0.1 mol/L hydrochloric acid or 0.1 mol/L sodium hydroxide solution) [ 83 , 89 ]. The flasks were kept at room temperature (25 °C) and 180 rpm, and samples were collected at different time intervals; phosphorus concentration was determined by ammonium molybdate spectrophotometry, and the corresponding removal capacity was calculated [ 83 ]. The calculation formula used to determine the phosphorus removal capacity (mg/g) is Equation (3).…”

“…The effect of contact time on phosphorus adsorption was observed for each adsorbent material according to the following procedure: in five different Erlenmeyer flasks (250 mL) 0.1 g adsorbent material was added; the phosphorus solution was added in 15 mL phosphorus solution with concentration of 400 mg/L and pH 7.5 (adjusted with 0.1 mol/L hydrochloric acid or 0.1 mol/L sodium hydroxide solution) [ 83 ]. The flasks were kept at room temperature (25 °C) and 180 rpm, and samples were collected at different times (0–400 min).…”

“…Furthermore, studies on the use of cobalt ferrite for phosphorus removal are relatively few and mainly refer to various materials that contain cobalt ferrite. To our best knowledge, this study is the first to report on the possible use of cobalt ferrite to remove phosphorus from wastewater [ 83 , 84 , 85 ].…”