Silylated Thiol-Containing Cellulose Nanofibers as a Bio-Based Flocculation Agent for Ultrafine Mineral Particles of Chalcopyrite and Pyrite

A considerable amount of very fine particles can be found, e.g., stored in tailing ponds, and they can include valuable or hazardous minerals that have the potential to be recovered. Selective flocculation, i.e., the formation of larger aggregates from specific minerals, offers a promising approach to improve the recovery of ultrafine particles. This study focuses on the use of a new bio-based flocculation agent made of silylated cellulose nanofibers containing a thiol-functional moiety (SiCNF). Flocculation was performed in separated systems of ultrafine mineral dispersions of pyrite, chalcopyrite, and quartz in aqueous alkaline medium. The flocculation performance of SiCNF was addressed in terms of the turbidity reduction of mineral dispersions and the floc size, and the results were compared with the performance of a commercial anionic polyacrylamide. SiCNF exhibited a turbidity removal efficiency of approximately 90%–99% at a concentration of 4000–8000 ppm with chalcopyrite and pyrite, whereas the turbidity removal of quartz suspension was significantly lower (a maximum of approximately 30%). The sulfide particles formed flocs with a size of several hundreds of micrometers. The quartz in turn did not form any visible flocs, and the dispersion still had a milky appearance after dosing 12,000 ppm of the flocculant. These results open a promising path for the investigation of SiCNF as a selective flocculation agent for sulfide minerals. Graphical Abstract

Increasing Effect of Water Clarifiers on the Treatment of Polymer-Containing Oil Production Sewage

Residual anionic polyacrylamide in polymer-flooding oil production wastewater results in the formation of a thermodynamically stable system. In this study, the effects of three different types of medicaments, namely, cationic, anionic and nonionic agents, in dynamic treatments, such as adding a position, dosage and combined processes of chemical addition, on the oil removal rate of sewage were examined. In the treatment with a single agent, the oil removal rate of the cationic agent CQY-1 and the nonionic agent CHF-2 was ≥ 97.8%. The charge characteristics of different ionic agents for the combined dosing treatment indicated that the oil removal rate was better than that of a single agent; the combined dosing ratio was 50 mg/L CHP-1 and 50 mg/L CHP-2. At 80 mg/L CQY-1, the oil removal rate of the dynamic process was ≥ 98.8%, and the dosage of CQY-1 was reduced from 200 mg/L to 50–150 mg/L, which corresponded to a decrease of 25.0%–75.0%. Therefore, the combined dosing process effectively reduced the single dosage.

Effects of Amendments on Physicochemical Properties and Respiration Rate of Soil from the Arid Region of Northwest China

In arid regions, decreased soil fertility has adversely affected agricultural sustainability. The effects of different amendments in alleviating these issues and increasing soil fertility remain unclear. Herein, a two-year field experiment was conducted to evaluate the properties of grey desert soil and soil respiration (SR) dynamics under six different treatment groups: biochar (BC), leonardite (LD), anionic polyacrylamide (PAM−), cationic polyacrylamide (PAM+) powder, anionic polyacrylamide solution in water (PAM−W), and control (CK). We observed that the BC and LD amendments significantly altered soil pH, organic matter, available nitrogen, available phosphorus, cation exchange capacity, and SR. PAM amendment increased the SR as compared to the control, except in autumn, but PAM did not affect the soil properties. SR under different amendments showed strong seasonal patterns, the highest and lowest SR rates were observed in June and January, respectively. Amendments and seasonal dynamics significantly affected SR, but no interaction was observed between these factors. Temporal variation of SR was substantially influenced by soil temperature at 15 cm of soil depth. Temperature sensitivity of SR (Q10) increased with soil depth and decreased with amendment addition. SR was significantly affected by soil temperature, moisture, air temperature, and their interactions. The outcomes of this study suggested that the BC and LD amendments improved soil fertility and negated the net carbon accumulation by increasing the SR and Q10 in arid agriculture soil.