Effects of Alcell Lignin Methylolation and Lignin Adding Stage on Lignin-Based Phenolic Adhesives.

To investigate the effects of lignin methylolation and lignin adding stage on the resulted lignin-based phenolic adhesives, Alcell lignin activated with NaOH (AL) or methylolation (ML) was integrated into the phenolic adhesives system by replacing phenol at various adhesive synthesis stages or directly co-polymerizing with phenolic adhesives. Lignin integration into phenolic adhesives greatly increased the viscosity of the resultant adhesives, regardless of lignin methylolation or adding stage. ML introduction at the second stage of adhesive synthesis led to much bigger viscosity than ML or AL introduction into phenolic adhesives at any other stages. Lignin methylolation and lignin adding stage did not affect the thermal stability of lignin based phenolic adhesives, even though lignin-based adhesives were less thermally stable than NPF. Typical three-stage degradation characteristics were also observed on all the lignin-based phenolic adhesives. Three-ply plywoods can be successfully laminated with lignin based adhesives, and it was interesting that after 3 h of cooking in boiling water, the plywoods specimens bonded with lignin-based phenolic adhesives displayed higher bonding strength than the corresponding dry strength obtained after direct conditioning at 20 °C and 65% RH. Compared with NPF, lignin introduction significantly reduced the bonding strength of lignin based phenolic adhesives when applied for plywood lamination. However, no significant variation of bonding strength was detected among the lignin based phenolic adhesives, regardless of lignin methylolation or adding stages.

Efficient removal of cadmium from soil-washing effluents by garlic peel biosorbent.

Paddy field soil contaminated by cadmium may produce cadmium-contained corns causing Itai-itai disease, and in situ washing of soil with the organic acid is a good technical choice due to its convenience and cost-effectiveness. While the bottleneck of this technique is how to recycle the huge volume of washing effluent in an efficient and economical way. Biosorption of cadmium on the garlic peel was attempted in present study and it was found quite satisfactorily effective to remove all cadmium from the real soil leaching effluent after three-time sequential adsorption. The systematical investigation on the effect of various parameters on the adsorption of cadmium on garlic peel in the existence of tartaric ligand was performed and it was found that tartrate could change Cd2+ into Cd(tar)0 species whose electrical charge state would restrain its approach to the adsorbent particles. The porous microstructure in the transversal surface of garlic peel and the abundant groups of -COOH are the main factors affecting the adsorption capability. A demonstrative flowsheet of soil remediation by chemical washing coupled with biosorption was proposed correspondingly, in which the cadmium could be recovered from the soil washing effluent, and the recovered effluent was reused for next soil washing, and recovered garlic peel was reused for cadmium adsorption from the effluents again, showing a great prospect in the remediation of paddy field soil contaminated by cadmium. Garlic peel was used to remove the cadmium from the soil washing effluent.

Removal of cadmium from a citrate-bearing solution by floatable microsized garlic peel.

Paddy field soil contaminated by cadmium may produce cadmium-containing corn due to the paddy's strong ability to accumulate cadmium. The in situ washing of soil with an organic acid is one of the suitable technical choices for the remediation of cadmium-contaminated soils. The limiting factor of this method lies in the recycling and reuse of the huge amount of washing effluent in an efficient and economical way. In present study, the simulated solutions were used to examine the adsorption efficiency of cadmium on a biosorbent which was synthesized by using garlic peel as the raw material. The biosorption behavior of cadmium on garlic peel was systematically studied in the presence of a citrate ligand. Presented here for the first time, garlic peel with buoyant properties was carefully collected and used for the preparation of the adsorbent, and verified to have a prominent advantage in efficiently separating from the solution after adsorption because of its floatability. Results show that the presence of citrate has a significant inhibition effect on the adsorption behavior of cadmium on the floating garlic peel, at the optimal pH of 4.0, which can be ascribed to the competitive affinity to the cadmium from the citrate ligand. SEM shows that floating garlic peel has a ruffled epidermis in the flat surface and porous microstructure in the transversal surface, making it durable enough and favorable for adsorption; and -COOH was determined by FTIR to be the main functional group contributing to the adsorption capability of garlic peel. Cadmium can be eluted off the garlic peel after adsorption, and the garlic peel can be then reused for the next cycle of adsorption with little decrease in adsorption capacity, even after ten adsorption/desorption cycles. The real leach liquor of cadmium-contaminated soil sample by 0.01 mol L-1 citric acid solution was used for testing, and it was found that after three adsorption uses, almost all the cadmium in the leach liquor had been recovered by the floating garlic peel. The above research results provided a possible route to recycle the soil washing solution by biosorption, giving a great perspective in the remediation of paddy field soil contaminated by cadmium.