Preparation of Metal Modified onto Biochar from Hazardous Waste for Arsenic Removal.

Use of urban sludge, hospital sludge, and aquatic product sludge as a biochar adsorbent from wastewater treatment plants was investigated. Microwave carbonization was used to carbonize the sludge and then chemically activated at high temperatures to increase porosity and surface area. Effective of arsenic adsorption in water presents a newly designed metal doped to biochar. The biochar was characterized by scanning electron microscope (SEM) with energy dispersive X-ray (EDS), nitrogen adsorption/desorption isotherm analyzer (BET), thermo gravimetric analysis (TGA) and X-ray diffraction (XRD) analysis. Results display uniform pore sizes and high surface area (>490 m²g-1) of the biochar. Thence, urban sludge, hospital sludge, and aquatic product sludge can be used as carbon sources. The highest amount of Fe, Mn, and Ni loading onto the biochar was determined to be 8.0%, 6.0% and 10.0%, respectively. All biochar samples have arsenic adsorption capacities positively correlated with initial concentration. The corresponding removal efficiency of As(V) is 98% and As(III) is 84% at pH 3 with an adsorption capacity of 4.12 and 3.6 mg g-1, respectively. The adsorption capacity of As(V) and As(III) clearly decreased in the presence of PO43- (2.34 and 1.46 mg g-1, respectively). Due to competition for adsorption sites, the PO43- can effectively reduce arsenic adsorption. The arsenic species adsorption-desorption recycles on biochar are also discussed.

Recycle of synthetic calcium fluoride and waste sulfuric acid to produce electronic grade hydrofluoric acid.

An innovative method for utilizing synthetic calcium fluoride (CaF2), recovered from fluoride-containing semiconductor wastewater, and waste sulfuric acid (H2SO4) to produce hydrofluoric acid (HF) was investigated. The research was set to study the low-temperature production of HF via reaction of synthetic CaF2 and waste H2SO4. The impact of four factors, including H2SO4 concentration, total volume (H2SO4 + H2O)/CaF2 ratio, drying temperature of synthetic CaF2, and reaction carried out under different temperature, on HF productivity was investigated in this study. HF yield increased with increasing H2SO4 concentration and total volume/CaF2 ratio under room temperature. Generally, reactions carried out under low-temperature (< 100 °C) had a positive impact on HF yield. The higher temperature led to an increase in absorbed-HF but a decrease in total-HF. The reaction of commercial CaF2 and 70% H2SO4 had a higher absorbed-HF yield of 61.7% than synthetic CaF2 and 70% waste H2SO4, which had a yield of 36%. This was due to the higher purity of the commercial CaF2 and fewer interference ions in H2SO4. HF productivity was lowered by CaSO4, which hindered the reaction of reactants and also the generation of fluorosulfuric acid.

Preparation of Fe-SBC from Urban Sludge for Organic and Inorganic Arsenic Removal.

In the process of water treatment adsorption has been proved to be the best, because of its significant advantages. It is recognized that recycling and reuse of waste can result in significant savings in materials cost. In this research, the adsorption of organic and inorganic arsenic using sludge biochar (SBC) made from urban sludge were analyzed. The sludge was carbonized using calciner carbonization and then chemically activated at high temperatures and a newly designed Fe-doped sludge biochar (Fe-SBC) presents effective As adsorption in water. Results show that the surface area and average pore volume of Fe-SBC are 498 m² g-1 and 0.33 cm³ g-1, respectively. The adsorption capacity of p-ASA, As(V) and As(III) on Fe-SBC was calculated as 5.47, 3.83 and 3.24 mg L-1, respectively. The adsorption capacity of As were obviously decreased in presence of PO3-4. After six times recycles of adsorption-desorption processes, the adsorption capacity of p-ASA, As(V) and As(III) on Fe-SBC obvious reduction.

Hexamethyldisilazane Removal with Mesoporous Materials Prepared from Calcium Fluoride Sludge.

A large amount of calcium fluoride sludge is generated by the semiconductor industry every year. It also requires a high amount of fuel consumption using rotor concentrators and thermal oxidizers to treat VOCs. The mesoporous adsorbent prepared by calcium fluoride sludge was used for VOCs treatment. The semiconductor industry employs HMDS to promote the adhesion of photo-resistant material to oxide(s) due to the formation of silicon dioxide, which blocks porous adsorbents. The adsorption of HMDS (Hexamethyldisiloxane) was tested with mesoporous silica materials synthesized from calcium fluoride (CF-MCM). The resulting samples were characterized by XRD, XRF, FTIR, N2-adsorption-desorption techniques. The prepared samples possessed high specific surface area, large pore volume and large pore diameter. The crystal patterns of CF-MCM were similar with Mobil composite matter (MCM-41) from TEM image. The adsorption capacity of HMDS with CF-MCM was 40 and 80 mg g-1, respectively, under 100 and 500 ppm HMDS. The effects of operation parameters, such as contact time and mixture concentration, on the performance of CF-MCM were also discussed in this study.

Preparation of Zn-Doped Biochar from Sewage Sludge for Chromium Ion Removal.

Recycling and reuse waste can result in significant savings in materials and energy. In this study, the adsorption of Cr(VI) was analyzed using activated carbon (AC) and biochar (BSC) made from sewage sludge. BSC materials were synthesized using zinc chloride as an activator coupled with carbonized sewage sludge. Specific surface area, pore size distribution, and pore volume were determined by measuring nitrogen adsorption-desorption (BET). BSC morphology was measured using field-emission scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS). Results showed that the surface area and average pore volume of the BSC were 490 m2 g-1 and 0.8 cm3 g-1, respectively. SEM results revealed that BSC had uniform pore size. Effects of varying the initial Cr(VI) concentrations, pH values, and dosages of BSC on adsorption performance were also determined. Results showed that the maximum removal efficiency of Cr(VI) was above 99%, and adsorption capacity of 50% ZnCl2-BSC was 677 mg g-1.